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By [[IBM]]
{{IBM-Reprint}}
 
=== About this Reference ===


== About this Reference ==
The following notations are used in this reference:
The following notations are used in this reference:
{|
|'''KEYWORD'''||Commands and language keywords.
|-
|'''KEYWORD'''||The default value for a command or language keyword when multiple values are possible but none are actually specified.
|-
|Phrase||Typically indicates a hypertext link to a separate panel containing a description for that phrase.
|-
|''Parameter''||Parameters whose actual names or values are to be supplied by the programmer.
|-
|'''''Definition'''''||A term being defined for the first time, or special emphasis.
|-
|Subscript||Subscripted text.
|-
|Superscript||Superscripted text (other than ý).
|-
|<Name>||A text value represented by "Name" is to be substituted in place of <Name> typically at assembler run-time.
|}


'''KEYWORD'''Commands and language keywords.
== Assembly Language Processor (ALP) Overview ==
The Assembly Language Processor (ALP) is an assembler that runs under OS/2 Warp. ALP is a functional replacement for the Microsoft Macro Assembler (MASM) and accepts:
* The full syntax of the Intel 80X86 architecture
* The full syntax of the MASM 5.10 high-level directive language
* A subset of the MASM 6.00 high-level directive language


''KEYWORD''The default value for a command or language keyword when multiple values are possible but none are actually specified.
ALP generates standard Object Module Format (OMF) files that can be linked to produce DOS or OS/2 executables. It can also generate symbolic debugging information compatible with the IBM family of source code debuggers. A MASM 5.10-compatible command line utility (MASM2ALP) is also provided to enable use of ALP with little or no change to existing build environments.


Phrase Typically indicates a hypertext link to a separate panel containing a description for that phrase.
ALP also offers a rich set of command line options, as well as a comprehensive listing output cabability that is highly configurable, allowing a visual perspective not possible with other assemblers.


''Parameter''Parameters whose actual names or values are to be supplied by the programmer.
* [[ALP Programming Guide and Reference/Installation|Installation]]


'''''Definition''A term being defined for the first time, or special emphasis.'''
*[[ALP Programming Guide and Reference/Understanding ALP|Understanding ALP]]


Subscript Subscripted text.
* [[ALP Programming Guide and Reference/Using ALP|Using ALP]]


Superscript Superscripted text (other than ý).
== Language Elements ==
;Description
The following sections describe the elements you use to build an ALP program source file.


&lt;Name&gt; A text value represented by &quot;Name&quot; is to be substituted in place of &lt;Name&gt;, typically at assembler run-time. <br />
'''Character Set'''


=== Assembly Language Processor (ALP) Overview ===
All elements in an assembler language source file are built from collections of characters contained in the '''character set''', which are defined as:


The Assembly Language Processor (ALP) is an assembler that runs under OS/2 Warp. ALP is a functional replacement for the Microsoft Macro Assembler ( MASM) and accepts:
* The uppercase and lowercase letters of the English alphabet
* The decimal digits 0 through 9
* The following graphic characters:
~  !  "  #  $  %  ^  &  '  (   )   |
*  +  ,  -  .  /   :   ;  =  <  >  ?
[  \  ]  _  {  }  @


* The full syntax of the Intel 80X86 architecture
* The space and horizontal tab characters
* The full syntax of the MASM 5.10 high-level directive language
* The end of line character(s)
* A subset of the MASM 6.00 high-level directive language <br />


ALP generates standard Object Module Format (OMF) files that can be linked to produce DOS or OS/2 executables. It can also generate symbolic debugging information compatible with the IBM family of source code debuggers. A MASM 5.10-compatible command line utility (MASM2ALP) is also provided to enable use of ALP with little or no change to existing build environments.
'''White Space'''


ALP also offers a rich set of command line options, as well as a comprehensive listing output cabability that is highly configurable, allowing a visual perspective not possible with other assemblers.
White space is a character or contiguous stream of characters that is ignored or removed from the input stream by the ALP preprocessor.


=== Installation ===
'''White space characters''' are any contiguous sequence of one or more space or tab characters not enclosed in single or double quotes. White space characters are significant only in that they serve to separate language tokens from one another; they are removed from the input stream by the scanner.


The following components are part of the ALP package:
;Syntax


'''ALP'''The assembler itself. These are the basic files that must be installed before the assembler can be used.
''Token:''
: ''Reserved-Word''
: ''Identifier''
: ''Literal''
: ''Punctuator''


'''MASM2ALP'''The MASM 5.10 Command Line Driver. The ALP component must be installed before the MASM2ALP utility can be utilized. <br />
=== Reserved Words ===
;Description
This section describes all of the assembler reserved words.


=== Installing ALP ===
;Syntax
''Reserved-Word:''
: ''Preprocessor-Directive''
: ''Assembler-Directive''
: ''Processor-Mnemonic''
: ''Processor-Register''
: ''Scalar-TypeName''
: ''Distance-TypeName''
: ''Language-Name''
: ''Anonymous-Label-Alias''
: ''Location-Counter-Alias''
: ''Indeterminate-Value-Alias''
: ''Directive-Keyword''
: ''Operator-Keyword''


ALP consists of two files: <br />
==== Preprocessor Directives ====
;Description
'''Preprocessor Directives''' are symbolic names that describe the various assembly-time text processing instructions interpreted by the preprocessor phase of the assembler.


<pre>alp . exe
;Syntax
alp . msg </pre>
''Preprocessor-Directive:'' one of
You can rename the root portions of the two file names if desired. In most cases, it does not matter whether the file names are in upper- or lowercase because the default OS/2 file systems disregard case. It is possible, however, that the use of an OS/2 Installable File System (IFS) might require that file names be referenced exactly as they are named with respect to upper- and lowercase. If this is true, then the root portion of the '''alp.exe'''and '''alp.msg'''file names (see [[00008.htm|BaseEXE]]) must be spelled identically and the ''.msg''extension on the messages file name must be specified in lowercase or the assembler will not be able to find the messages file at run time.
CATSTR      COMMENT    ELSE        ELSEIF
ELSEIF1    ELSEIF2    ELSEIFB    ELSEIFDEF
ELSEIFDIF  ELSEIFDIFI  ELSEIFE    ELSEIFIDN
ELSEIFIDNI  ELSEIFNB    ELSEIFNDEF  ENDIF
ENDM        EQU        EXITM      FOR
FORC        IF          IF1        IF2
IFB        IFDEF      IFDIF      IFDIFI
IFE        IFIDN      IFIDNI      IFNB
IFNDEF      INCLUDE    INSTR      IRP
IRPC        LOCAL      MACRO      PURGE
REPEAT      REPT        SIZESTR    SUBSTR


To install ALP on OS/2:
==== Assembler Directives ====
;Description
'''''Assembler Directives''''' are symbolic names that describe the various assembly-time instructions interpreted by the assembler itself.


1.Copy '''alp.exe'''into a directory of your choice. If the assembler will be invoked from the command line (rather than by absolute reference from a makefile or command file), then the selected directory should be among those referenced by the [[00033.htm|PATH]]environment variable.
;Syntax
''Assembler-Directive:'' one of
.186          .286          .286C        .286P
.287          .386          .386C        .386P
.387          .486          .486C        .486P
.586          .586P        .686          .686P
.8086        .8087          ALIGN        .ALPHA
  ASSUME      %BIN          .CODE          COMM
.CONST        .CREF        .DATA        .DATA?
  DB            DD            DF            DOSSEG
.DOSSEG        DQ            DT            DW
  ECHO          END          ENDP          ENDS
  EQU          .ERR          .ERR1        .ERR2
.ERRB        .ERRDEF      .ERRDIF      .ERRDIFI
.ERRE        .ERRIDN      .ERRIDNI      .ERRNB
.ERRNDEF      .ERRNZ        EVEN          EXTERN
  EXTERNDEF    EXTRN        .FARDATA      .FARDATA?
  GROUP        INCLUDELIB    LABEL        .LALL
.LFCOND      .LIST        .LISTALL      .LISTIF
.LISTMACRO    .LISTMACROALL  LOCAL        .MMX
.MODEL        NAME        .NOCREF      .NOLIST
.NOLISTIF    .NOLISTMACRO  .NOMMX        OPTION
  ORG          %OUT          PAGE          PROC
  PUBLIC      .RADIX        RECORD      .SALL
  SEGMENT      .SEQ          .SFCOND      .STACK
  STRUC        STRUCT        SUBTITLE      SUBTTL
.TFCOND        TITLE        TYPEDEF      UNION
.XALL        .XCREF        .XLIST


2.For best performance, the '''alp.msg'''file should be copied into the same directory used in step 1 or in a directory referenced by the [[00030.htm|&lt;BaseEXE&gt;_PATH]] environment variable. It is not necessary to set any additional environment variables if the first method is used.
==== Processor Mnemonics ====
;Description
'''Processor Mnemonics''' are symbolic names given to the various instructions in the processor instruction set.


Alternatively, a directory referenced by the [[00031.htm|DPATH]]environment variable may also be used, but performance may be degraded during initialization, since the assembler must search all of the listed directories for the '''alp.msg''' file. See [[00006.htm|The ALP Messages File]]for more information.
;Syntax
''Processor-Mnemonic:'' one of


3.Optionally, default values for command line options may be established. See [[00029.htm|&lt;BaseEXE&gt;_OPTIONS]]for more information. <br />
AAA        AAD        AAM        AAS        ADC
ADD        AND        ARPL      BOUND      BSF
BSR        BSWAP      BT        BTC        BTR
BTS        CALL      CBW        CDQ        CLC
CLD        CLI        CLTS      CMC        CMOVA
CMOVAE    CMOVB      CMOVBE    CMOVC      CMOVE
CMOVG      CMOVGE    CMOVL      CMOVLE    CMOVNA
CMOVNAE    CMOVNB    CMOVNBE    CMOVNC    CMOVNE
CMOVNG    CMOVNGE    CMOVNL    CMOVNLE    CMOVNO
CMOVNP    CMOVNS    CMOVNZ    CMOVO      CMOVP
CMOVPE    CMOVPO    CMOVS      CMOVZ      CMP
CMPS      CMPSB      CMPSD      CMPSW      CMPXCHG
CMPXCHG8B  CPUID      CWD        CWDE      DAA
DAS        DEC        DIV        EMMS      ENTER
ESC        F2XM1      FABS      FADD      FADDP
FBLD      FBSTP      FCHS      FCLEX      FCMOVB
FCMOVBE    FCMOVE    FCMOVNB    FCMOVNBE  FCMOVNE
FCMOVNU    FCMOVU    FCOM      FCOMI      FCOMIP
FCOMP      FCOMPP    FCOS      FDECSTP    FDISI
FDIV      FDIVP      FDIVR      FDIVRP    FENI
FFREE      FIADD      FICOM      FICOMP    FIDIV
FIDIVR    FILD      FIMUL      FINCSTP    FINIT
FIST      FISTP      FISUB      FISUBR    FLD
FLD1      FLDCW      FLDENV    FLDENVD    FLDENVW
FLDL2E    FLDL2T    FLDLG2    FLDLN2    FLDPI
FLDZ      FMUL      FMULP      FNCLEX    FNDISI
FNENI      FNINIT    FNOP      FNSAVE    FNSAVED
FNSAVEW    FNSTCW    FNSTENV    FNSTENVD  FNSTENVW
FNSTSW    FPATAN    FPREM      FPREM1    FPTAN
FRNDINT    FRSTOR    FRSTORD    FRSTORW    FSAVE
FSAVED    FSAVEW    FSCALE    FSETPM    FSIN
FSINCOS    FSQRT      FST        FSTCW      FSTENV
FSTENVD    FSTENVW    FSTP      FSTSW      FSUB
FSUBP      FSUBR      FSUBRP    FTST      FUCOM
FUCOMI    FUCOMIP    FUCOMP    FUCOMPP    FWAIT
FXAM      FXCH      FXTRACT    FYL2X      FYL2XP1
HLT        IDIV      IMUL      IN        INC
INS        INSB      INSD      INSW      INT
INTO      INVD      INVLPG    IRET      IRETD
IRETDF    IRETF      JA        JAE        JB
JBE        JC        JCXZ      JE        JECXZ
JG        JGE        JL        JLE        JMP
JNA        JNAE      JNB        JNBE      JNC
JNE        JNG        JNGE      JNL        JNLE
JNO        JNP        JNS        JNZ        JO
JP        JPE        JPO        JS        JZ
LAHF      LAR        LDS        LEA        LEAVE
LES        LFS        LGDT      LGS        LIDT
LLDT      LMSW      LOCK      LODS      LODSB
LODSD      LODSW      LOOP      LOOPD      LOOPE
LOOPED    LOOPEW    LOOPNE    LOOPNED    LOOPNEW
LOOPNZ    LOOPNZD    LOOPNZW    LOOPW      LOOPZ
LOOPZD    LOOPZW    LSL        LSS        LTR
MOV        MOVD      MOVQ      MOVS      MOVSB
MOVSD      MOVSW      MOVSX      MOVZX      MUL
NEG        NOP        NOT        OR        OUT
OUTS      OUTSB      OUTSD      OUTSW      PACKSSDW
PACKSSWB  PACKUSWB  PADDB      PADDD      PADDSB
PADDSW    PADDUSB    PADDUSW    PADDW      PAND
PANDN      PCMPEQB    PCMPEQD    PCMPEQW    PCMPGTB
PCMPGTD    PCMPGTW    PMADDWD    PMULHW    PMULLW
POP        POPA      POPAD      POPD      POPF
POPFD      POPW      POR        PSLLD      PSLLQ
PSLLW      PSRAD      PSRAW      PSRLD      PSRLQ
PSRLW      PSUBB      PSUBD      PSUBSB    PSUBSW
PSUBUSB    PSUBUSW    PSUBW      PUNPCKHBW  PUNPCKHDQ
PUNPCKHWD  PUNPCKLBW  PUNPCKLDQ  PUNPCKLWD  PUSH
PUSHA      PUSHAD    PUSHD      PUSHF      PUSHFD
PUSHW      PXOR      RCL        RCR        RDMSR
RDPMC      RDTSC      REP        REPE      REPNE
REPNZ      REPZ      RET        RETF      RETN
ROL        ROR        RSM        SAHF      SAL
SAR        SBB        SCAS      SCASB      SCASD
SCASW      SETA      SETAE      SETB      SETBE
SETC      SETE      SETG      SETGE      SETL
SETLE      SETNA      SETNAE    SETNB      SETNBE
SETNC      SETNE      SETNG      SETNGE    SETNL
SETNLE    SETNO      SETNP      SETNS      SETNZ
SETO      SETP      SETPE      SETPO      SETS
SETZ      SGDT      SHL        SHLD      SHR
SHRD      SIDT      SLDT      SMSW      STC
STD        STI        STOS      STOSB      STOSD
STOSW      STR        SUB        TEST      UC2
VERR      VERW      WAIT      WBINVD    WRMSR
XADD      XCHG      XLAT      XLATB      XOR


=== Installing MASM2ALP ===
==== Processor Registers ====
;Description
'''Processor Registers''' are the symbolic names assigned to the various internal processor registers. They are normally used as operands to processor instructions.


The MASM2ALP utility consists of a single file: <br />
;Syntax
''Processor-Register:''
: ''General-Purpose-Register''
: ''Segment-Register''
: ''Control-Register''
: ''Debug-Register''
: ''Test-Register''
: ''MMX-Register''
: ''Floating-Point-Register''


<pre>masm2alp . exe </pre>
''General-Purpose-Register:''
To install MASM2ALP on OS/2:
: ''8-Bit-Register''
: ''16-Bit-Register''
: ''32-Bit-Register''


1.Copy '''masmalp.exe'''into a directory of your choice. If the utility will be invoked from the command line (rather than by absolute reference from a makefile or command file), then the selected directory should be among those referenced by the [[00033.htm|PATH]]environment variable.
''8-Bit-Register:'' one of
: '''AL AH BL BH CL CH DL DH'''


It is recommended that both '''masm2alp.exe'''and '''alp.exe'''be installed in the same directory, especially in build environments where reliance on environment variables is discouraged. If '''masm2alp.exe'''is invoked by absolute path name (rather than via a [[00033.htm|PATH]]search), it will use that same path when it first attempts to execute '''alp.exe'''. This technique allows execution of '''alp.exe'''without requiring it to be referenced in the [[00033.htm|PATH]]. If the search fails, the path name prefix will be removed and MASM2ALP will rely on the operating system to locate '''alp.exe'''.
''16-Bit-Register:'' one of  
: '''AX BX CX DX DI SI BP SP'''


2.If you also use the Microsoft Macro Assembler, you must decide if MASM2ALP will replace MASM or co-exist with it. This usually means renaming the MASM executable ('''masm.exe''') to something else, then renaming '''masm2alp.exe'''to '''masm.exe'''. Alternatively, you may choose to leave the names unchanged, taking manual steps in your makefiles or build scripts to insure that the correct executables are referenced from your build environment.
''32-Bit-Register:'' one of
: '''EAX EBX ECX EDX EDI ESI EBP ESP'''


3.Optionally, default values for command line options may be established by defining the '''MASM'''environment variable. MASM2ALP interprets the contents of this environment variable before processing the command line. Any values set in this manner are translated and passed to '''alp.exe'''via the command line. The [[00029.htm|&lt;BaseEXE&gt;_OPTIONS]]environment variable used by '''alp.exe''' is not queried or modified by MASM2ALP.
''Segment-Register:'' one of  
: '''CS DS ES FS GS SS'''


4.If it becomes necessary to analyze a problem with MASM2ALP (such as failure to invoke '''alp.exe''', or other unexpected behavior), defining the '''ALP_ ECHO'''environment variable to any non-empty value will cause MASM2ALP to echo the generated command line to the standard output device. <br />
''Control-Register:'' one of
: '''CR0 CR2 CR3 CR4'''


=== Understanding ALP ===
''Debug-Register:'' one of
: '''DR0 DR1 DR2 DR3 DR4 DR5 DR6 DR7'''


This chapter describes:
''Test-Register:'' one of
*The ALP message file
: '''TR3 TR4 TR5 TR6 TR7'''
*ALP internal variables


Though you do not need to understand this information to be able to use ALP , you may need this information for troubleshooting purposes.
''MMX-Register:'' one of
: '''MM0 MM1 MM2 MM3 MM4 MM5 MM6 MM7'''


=== The ALP Messages File ===
''Floating-Point-Register:''
'''ST'''


Nearly every message displayed by ALP at run time is stored in a separate message file. The exception to this rule are messages that are displayed if the message file cannot be opened: ALP ends if one of these messages is displayed.
==== Scalar Type Names ====
;Description
'''Scalar Type Names''' are the symbolic names given to the integral data types. These are the fundamental types of data upon which the processor can directly operate.


When ALP starts, it determines the name of the message file by creating a name of the form &lt;[[00008.htm|BaseEXE]]&gt;'''.msg'''(see [[00008.htm|BaseEXE]]). Once ALP knows the name of the message file, ALP searches the following directories in the following order for the file:
;Syntax
''Scalar-TypeName:''
: '''BYTE'''
: '''SBYTE'''
: '''WORD'''
: '''SWORD'''
: '''DWORD'''
: '''SDWORD'''
: '''REAL4'''
: '''FWORD'''
: '''QWORD'''
: '''REAL8'''
: '''TBYTE'''
: '''REAL10'''


1.Current directory <br /> 2.The directory contained in the [[00009.htm|BasePATH]]internal variable <br /> 3.Each of the directories specified in the [[00008.htm|BaseEXE]]internal variable <br /> 4.Each of the directories specified in the [[00033.htm|PATH]]environment variable <br /> 5.Each of the directories specified in the [[00031.htm|DPATH]]environment variable <br />
==== Distance Type Names ====
;Description
'''Distance Type Names''' are the symbolic names given to the integral types of pointers directly supported by the processor. Their names reflect a fundamental property of the Intel processor architecture known as ''distance''. The type of pointer is defined by the ''distance'' required to reach the information to which it points.


=== Internal Variables ===
;Syntax
''Distance-TypeName:''
: '''NEAR'''
: '''NEAR16'''
: '''NEAR32'''
: '''FAR'''
: '''FAR16'''
: '''FAR32'''


ALP maintains a set of ''internal variables''that it uses for various purposes . These variables reflect the ALP environment; programmers do not use these variables. Their values may be indirectly affected by the user of ALP , for instance, through the use of various command line options.
==== Language Names ====
;Description
'''Language Names''' refer to the various high level programming languages (or more specifically, the calling conventions used by such languages) with which the assembler has the ability to interface.


;Syntax
''Language-Name:''
: '''C'''
: '''SYSCALL'''
: '''STDCALL'''
: '''PASCAL'''
: '''FORTRAN'''
: '''BASIC'''
: '''OPTLINK'''


=== BaseEXE ===
==== Anonymous Label Aliases ====
;Description
The '''''Anonymous Label Aliases''''' are reserved symbolic names that return a context-sensitive value when referenced in expressions.


When ALP is invoked, if the full path name of the ALP executable was provided by the operating system, then the &quot;base&quot; portion is isolated and used to construct the value of the '''BaseEXE'''internal variable. For instance , if the user invoked ALP and the name of the executable was made available as &quot;C:\TOOLS\ALP.EXE&quot;, then the '''BaseEXE'''internal variable would contain the value &quot;ALP&quot;. The value of '''BaseEXE'''is used to differentiate ALP-specific components in the environment (such as data files or environment variables) from those that are globally accessible to all programs. Even multiple versions of ALP can coexist without environmental &quot;collisions&quot; simply by copying and renaming the ALP executable and its associated message file.
The reserved name '''@B''' (backward reference) returns the internally generated name representing the nearest '''@@:''' code label appearing before the current location in the input stream.


If the file name of the ALP executable is '''not'''available at run time, then the value of '''BaseEXE'''defaults to &quot;ALP&quot;.
The reserved name '''@F''' (forward reference) returns the internally generated name representing the nearest '''@@:''' code label appearing after the current location in the input stream.


;Syntax
''Anonymous-Label-Alias:''
: '''@B'''
: '''@F'''


==== Location Counter Alias ====
;Description
The '''''Location Counter Alias''''' is a reserved name used in expressions to return the offset within the current segment or structure being assembled.


=== BasePATH ===
;Syntax
''Location-Counter-Alias:''
: '''$'''


When ALP is invoked, if the full path name of the ALP executable was provided by the operating system, then the &quot;path&quot; portion is isolated and used to construct the value of the '''BasePATH'''internal variable. For instance, if the user invoked ALP and the name of the executable was made available as &quot;C:\TOOLS\ALP.EXE&quot;, then the '''BasePATH'''internal variable would contain the value &quot;C:\TOOLS\&quot;. The value of '''BasePATH'''can be used to locate ALP-specific components in the environment (such as the ALP messages file) without the need to store this information in an alternate environment variable such as DPATH. Check your operating system documentation to see if it feasible to use the '''BasePATH'''method of locating ALP components.
==== Indeterminate Value Alias ====
;Description
The '''''Indeterminate Value Alias''''' is a reserved name used in expressions to represent an uninitialized value.


If the file name of the ALP executable is '''not'''available at run time, then the value of '''BasePATH'''is NULL.
;Syntax
''Indeterminate-Value-Alias:''
: '''?'''


==== Directive Keywords ====
;Description
'''''Directive Keywords''''' are symbolic names recognized and used in the body of various assembler directives.


=== IncDIR ===
;Syntax
''Directive-Keyword:''
ABS        AT            BASIC        C
CASEMAP    CODE          COMMON        DOTNAME
EMULATOR    EPILOGUE      ERROR        EXPORT
EXPR16      EXPR32        FARSTACK      FLAT
FORTRAN    HUGE          LANGUAGE      LARGE
LJMP        MEDIUM        NEARSTACK    NODOTNAME
NOEMULATOR  NOKEYWORD    NOLANGUAGE    NOLJMP
NONE        NOOLDMACROS  NOOLDSTRUCTS  NOREADONLY
NOSCOPED    NOSIGNEXTEND  NOTHING      NOTPUBLIC
OLDMACROS  OLDSTRUCTS    OPTLINK      OS_DOS
OS_OS2      PAGE          PARA          PASCAL
PRIVATE    PROC          PROLOGUE      PUBLIC
READONLY    SCOPED        SEGMENT      SIGNEXTEND
SMALL      STACK        STDCALL      SYSCALL
TINY        USE16        USE32        USES


This variable contains the empty string unless explicitly initialized with the '''Fdi'''parameterized command line option; it contains the cumulative value of all the specified include paths.
==== Operator Keywords ====
;Description
'''''Operator Keywords''''' are symbolic names used in expressions to denote an operation to be performed on one or more operands.


Related Information:
;Syntax
''Operator-Keyword:''
AND        DUP        EQ          GE
GT          HIGH        HIGHWORD    LE
LENGTH      LENGTHOF    LOW        LOWWORD
LT          MASK        MOD        NE
NOT        OFFSET      OPATTR      OR
PTR        SEG        SHL        SHORT
SHR        SIZE        SIZEOF      THIS
.TYPE      TYPE        WIDTH      XOR


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00053.htm|Fdi - Specify Include File Search Path]] <br />
=== Identifiers ===
;Description
This section describes the syntax for identifiers and the various types of information they can be made to represent.


;Syntax
''Identifier:''
: ''Normal-Identifier''
: ''Dot-Identifier''
: ''Normal-Identifier''
: ''NonDigit''
: ''Normal-Identifier Identifer-Character''


=== IncEXT ===
''Dot-Identifier''
''. Normal-Identifier''


This variable contains the default include file name extension that is conditionally appended to unadorned file names generated by the '''INCLUDE''' preprocessor directive. The default value for '''IncEXT'''is &quot;.inc&quot; unless altered by use of the '''Fei'''parameterized command line option.
''Identifier-Character''
''NonDigit''
''Digit''


Related Information:
''NonDigit:'' one of
_ $ @ ?
a b c d e f g h i j k l m
n o p q r s t u v w x y z
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00058.htm|Fei - Control Include File Extension (IncEXT)]] <br />
''Digit:'' one of
0 1 2 3 4 5 6 7 8 9


==== Identifier Types ====
;Description
This section describes the various types of identifiers that the assembler will create and manipulate.


;Definition
''Identifier-Type:''
: ''EquateName''
: ''FieldName''
: ''GroupName''
: ''LabelName''
: ''MacroName''
: ''SegmentName''
: ''UserDefined-TypeName''


=== LstDIR ===
===== Equate Name =====


This variable contains the empty string unless explicitly initialized with the '''Fdl'''parameterized command line option; it is only used if the value specified by the '''Fl'''command line option did not contain any path information.
;Definition


Related Information:
''EquateName:''
: ''Numeric-EquateName''
: ''Text-EquateName''


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00050.htm|Fl - Produce Listing File]] <br />�[[00054.htm|Fdl - Directory to Store Listing File (LstDIR)]] <br />
;Description
An ''EquateName'' is a symbolic identifier that is associated with an expression or a body of text. The assembler substitutes the value of the ''EquateName'' at the point of reference.


====== Numeric Equate Name ======
An identifier becomes a ''Numeric-EquateName'' when it is defined in a EQU or = directive. Procedure parameter names and local variable names are also created as ''Numeric-EquateNames'', but are visible only from within the procedure where they are defined. All other ''Numeric-EquateNames'' are globally-scoped identifiers visible across the entire module.


A ''Numeric-EquateName'' may only be referenced from within expressions, as its replacement value is itself an expression.


=== LstEXT ===
====== Text Equate Name ======
A ''Text-EquateName'' is a globally-scoped identifier created during the processing of a EQU preprocessor directive. A ''Text-EquateName'' is associated with a body of text whose content may not span across line breaks. In certain contexts the assembler replaces the ''Text-EquateName'' with the text that it represents and recursively evaluates the result.


This variable contains the default listing file name extension that is conditionally appended to the concatenated values of [[00012.htm|LstDIR]]and [[00014.htm|LstNAME]]; the assembler treats the resulting string as the fully qualified listing file name. The default value for '''LstEXT'''is &quot;.lst&quot; unless altered by use of the '''Fel'''parameterized command line option.
===== Field Name =====
;Definition
''FieldName:''
: ''Record-FieldName''
: ''Structure-FieldName''
: ''Union-FieldName''


Related Information:
;Description
An identifier becomes a ''FieldName'' when it is defined within a RECORD, STRUCT, or UNION directive.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00059.htm|Fel - Control Listing File Extension (LstEXT)]] <br />
====== Record Field Name ======
A ''Record-FieldName'' is a globally-scoped identifier created during the processing of a RECORD directive. It is a special variation of a ''Numeric-EquateName'' and can be used in the same contexts.


====== Structure Field Name ======
An identifier becomes a ''Structure-FieldName'' when it is defined in a STRUCT directive. If the assembler is operating in M510 mode, or if the OPTION OLDSTRUCTS directive has been specified, then a ''Structure-FieldName'' is a globally-scoped identifier treated as a special variation of a ''Numeric-EquateName'' and can be used in the same contexts. Otherwise, a ''Structure-FieldName'' is private to the defining structure and is only accessible in expressions through use of the Structure/Union Field Selection (. Operator).


====== Union Field Name ======
An identifier becomes a ''Union-FieldName'' when it is defined in a UNION directive. A ''Union-FieldName'' is private to the defining union and is only accessible in expressions through use of the Structure/Union Field Selection (. Operator).


=== LstNAME ===
===== Group Name =====
A ''GroupName'' is a globally-scoped identifier created during the processing of a GROUP directive. It is referenced from within expressions.


This variable contains the same value as the contents of [[00024.htm|SrcNAME]], unless initialized with the '''Fl'''parameterized command line option.
===== Label Name =====
;Definition
''LabelName:''
: ''Code-LabelName''
: ''Data-LabelName''


Related Information:
;Description
A ''LabelName'' is globally-scoped identifier that is associated with a program address at application run-time. It has an explicit or inherited ''Type-Declaration'', and an optional ''Language-Attribute''. These attributes are described in the following sections.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00050.htm|Fl - Produce Listing File]] <br />
;Type Declaration
The type declaration associated with a label name depends on how the label was defined. See the ''Code-LabelName'' and ''Data-LabelName'' sections for descriptions on how this attribute is assigned.


;Language Attribute
A ''LabelName'' can have an assigned ''Language-Attribute'', set either implicitly through the use of a ''Language-Name'' keyword in the body of a .MODEL or OPTION directive, or explicitly through the use of an overriding ''Language-Name'' keyword in the body of a EXTERN/EXTRN, EXTERNDEF, PROC, or PUBLIC directive. The ''Language-Attribute'' determines the exact spelling of the ''LabelName'' identifier when it is written to the object file. According to the ''Language-Attribute'', identifier spellings are modified from their appearance in the assembly language source module as follow:
{| class="wikitable"
!LANGUAGE ATTRIBUTE!!IDENTIFIER SPELLING
|-
|OPTLINK, SYSCALL||No modifications are made to the identifier when written to the object file.
|-
|C, STDCALL||A leading underscore character is appended to the front of the name.
|-
|BASIC, FORTRAN, PASCAL||All characters in the identifier are converted to uppercase.
|}


===== Code Label Name =====
;Definition
''Code-LabelName:''
: ''Target-LabelName''
: ''Procedure-LabelName''


=== MsgDIR ===
;Description
A ''Code-LabelName'' is an identifier that is associated with an executable code address at application run-time. There are two types of ''Code-LabelNames: Target-LabelNames'' and ''Procedure-LabelNames''.


This variable contains the empty string unless explicitly initialized with the '''Fdm'''parameterized command line option; it is only used if the value specified by the '''Fm'''command line option did not contain any path information.
====== Target Label Name ======
An identifier becomes a ''Target-LabelName'' when it is defined with a :, ::, or LABEL directive.


Related Information:
If a ''Target-LabelName'' created with a single colon (:) is defined within the body of a procedure, then the name is visible only from within that procedure unless operating in M510 mode (and no .MODEL directive with a ''Language-Name'' has been specified), or unless the OPTION NOSCOPED directive has been specified.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00051.htm|Fm - Produce Messages File]] <br />�[[00055.htm|Fdm - Directory to Store Messages File (MsgDIR)]] <br />
A ''Target-LabelName'' defined outside the body of a procedure is visible to the entire module, and may also be given PUBLIC visibility.


====== Procedure Label Name ======
An identifier becomes a ''Procedure-LabelName'' when it is defined in a '''PROC''' directive.


===== Data Label Name =====
A ''Data-LabelName'' is an identifier that is the address of a program variable at application run-time. An identifier becomes a ''Data-LabelName'' when it is named in a data allocation statement, or when a scalar, aggregate, or vector type is associated with the identifier named in a LABEL, EXTERN/ EXTRN, EXTERNDEF, or COMM directive.


=== MsgEXT ===
==== Macro Name ====
A ''MacroName'' is a globally-scoped identifier created during the processing of a '''MACRO''' directive. It is associated with a multi-line body of text. A ''MacroName'' may only be used in contexts where a normal assembler directive is expected.


This variable contains the default messages file name extension that is conditionally appended to the concatenated values of [[00015.htm|MsgDIR]]and [[00017.htm|MsgNAME]]; the assembler treats the resulting string as the fully qualified messages file name. The default value for '''MsgEXT'''is &quot;.msg&quot; unless altered by use of the '''Fem'''parameterized command line option.
===== Macro Parameter Name =====
An identifier becomes a ''Macro-ParameterName'' when it is named as a parameter to a macro in a '''MACRO''' directive. It is associated with a body of text whose content may not span across line breaks. It is only recognized and acted upon from within the body of a macro expansion.


Related Information:
==== Segment Name ====
A ''SegmentName'' is a globally-scoped identifier created during the processing of a SEGMENT directive. It may be referenced from within expressions or in the body of a GROUP directive.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00060.htm|Fem - Control Messages File Extension (MsgEXT)]] <br />
==== User-Defined Type Name ====
;Definition
''UserDefined-TypeName:''
: ''Record-TypeName''
: ''Structure-TypeName''
: ''Typedef-TypeName''
: ''Union-TypeName''


;Description
An identifier becomes a ''UserDefined-TypeName'' when it is defined within a RECORD, STRUCT, TYPEDEF, or UNION directive.


===== Record Type Name =====
A ''Record-TypeName'' is a globally-scoped identifier created during the processing of a RECORD directive. It is recognized from within ''Expressions'', ''Type-Declarations'', or as a pseudo-directive in a data allocation statement.


=== MsgNAME ===
===== Structure Type Name =====
A ''Structure-TypeName'' is a globally-scoped identifier created during the processing of a STRUCT directive. It is recognized from within ''Expressions'', ''Type-Declarations'', or as a pseudo-directive in a data allocation statement.


This variable contains the same value as the contents of [[00024.htm|SrcNAME]], unless initialized with the '''Fm'''parameterized command line option.
===== Typedef Type Name =====
A ''Typedef-TypeName'' is a globally-scoped identifier created during the processing of a TYPEDEF directive. It is recognized from within ''Expressions'', ''Type-Declarations'', or as a pseudo-directive in a data allocation statement.


Related Information:
===== Union Type Name =====
A ''Union-TypeName'' is a globally-scoped identifier created during the processing of a UNION directive. It is recognized from within ''Expressions'', ''Type-Declarations'', or as a pseudo-directive in a data allocation statement.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00051.htm|Fm - Produce Messages File]] <br />
=== Predefined Identifiers ===
The following sections describe the predefined identifiers created by the assembler. When a case-sensitive assembly is being performed, the predefined identifiers must be spelled exactly as they appear in the following descriptions with respect to uppercase and lowercase characters.


==== Segment Information ====
The following sections describe the predefined identifiers created by the assembler in support of segment manipulation.


===== @code =====
The '''@code''' identifier is a ''Text-EquateName'' created by the assembler when a .MODEL directive is encountered, at which time the assembler performs an automatic '''ASSUME CS:@code''' operation. The '''@code''' symbol is not defined if a .MODEL directive has not been issued.


=== ObjDIR ===
Under MASM 5.10 emulation, the '''@code''' symbol is set to the name of the implicitly-defined default code segment (the segment opened when a .CODE directive is used) and its value is never changed. In other modes, the '''@code''' symbol is updated to reflect whatever segment is opened by using .CODE, whether defined implicitly or as an explicit parameter to the .CODE directive.


This variable contains the empty string unless explicitly initialized with the '''Fdo'''parameterized command line option; it is only used if the value specified by the '''Fo'''command line option did not contain any path information.
The value assigned to the '''@code''' symbol when the default code segment is opened is determined by the memory model as follows:


Related Information:
'''Memory Model Value for @code'''
: TINY DGROUP
: SMALL _TEXT
: MEDIUM ''module'' _TEXT
: COMPACT_TEXT
: LARGE ''module'' _TEXT
: HUGE ''module'' _TEXT
: FLAT CODE32


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00052.htm|Fo - Produce Object File]] <br />�[[00056.htm|Fdo - Directory to Store Object File (ObjDIR)]] <br />
The ''module'' entry is replaced with base file name of the top-level module being assembled.


===== @CodeSize =====
The '''@CodeSize''' identifier is a ''Numeric-EquateName'' created by the assembler when a .MODEL directive is encountered. '''@CodeSize''' indicates whether code segments created by the .CODE directive are named such that the linker will combine them into a single (NEAR) segment or into multiple (FAR) segments. The '''@CodeSize''' symbol is set to 0 (NEAR) for the '''TINY, SMALL, COMPACT,''' and '''FLAT''' memory models, and to 1 (FAR) for the '''MEDIUM, LARGE,''' and '''HUGE''' memory models. The '''@CodeSize''' symbol is not defined if a .MODEL directive has not been issued.


===== @CurSeg =====
The '''@CurSeg''' identifier is a ''Text-EquateName'' defined by the assembler to hold the name of the currently opened segment. If no segment is currently open, '''@CurSeg''' will expand into an empty string.


=== ObjEXT ===
===== @data =====
The '''@data''' identifier is a ''Text-EquateName'' created by the assembler when a .MODEL directive is encountered. It expands to the group name shared by all of the near data segments. If a '''.MODEL FLAT''' has been issued, the '''@data''' identifier expands to FLAT. For all other memory models, it expands to DGROUP.


This variable contains the default object file name extension that is conditionally appended to the concatenated values of [[00018.htm|ObjDIR]]and [[00020.htm|ObjNAME]]; the assembler treats the resulting string as the fully qualified object file name. The default value for '''ObjEXT'''is &quot;.obj&quot; unless altered by use of the '''Feo'''parameterized command line option.
===== @DataSize =====
The '''@DataSize''' identifier is a ''Numeric-EquateName'' created by the assembler when a .MODEL directive is encountered, and represents the default data distance. Depending on the currently selected memory model, the '''@DataSize''' identifier is set to the following values:
: TINY 0
: SMALL 0
: COMPACT 1
: MEDIUM 1
: LARGE 1
: HUGE 2
: FLAT 0


Related Information:
===== @Model =====
The '''@Model''' identifier is a ''Numeric-EquateName'' created by the assembler when a .MODEL directive is encountered, and is set to a unique value for each memory model. The values are as follows:
: TINY 1
: SMALL 2
: COMPACT 3
: MEDIUM 4
: LARGE 5
: HUGE 6
: FLAT 7


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00061.htm|Feo - Control Object File Extension (ObjEXT)]] <br />
===== @WordSize =====
The '''@WordSize''' identifier is a ''Numeric-EquateName'' that reflects the address size attribute of the current segment. It is set to 2 for a '''USE16''' segment, and 4 for a '''USE32''' segment. If no segment is currently open, it reflects the default address size as determined by the currently selected processor.


==== Version Information ====
These identifiers offer methods of testing the various operating modes of the assembler to determine what features are activated or disabled, or how the assembler will behave under various conditions.


===== @Alp =====
The '''@Alp''' identifier is a ''Text-EquateName'' that can be tested to determine if ALP is assembling the source file (versus some other assembler). It is always set to the string '''100'''.


=== ObjNAME ===
===== @AlpMajor =====
The '''@AlpMajor''' identifier is a ''Text-EquateName'' that reflects the ''major'' portion of the three-part assembler version number. It is padded on the right with zeros to allow major version number comparisions independant of the minor version and revisions numbers. See @AlpVersion for more information.


This variable contains the same value as the contents of [[00024.htm|SrcNAME]], unless initialized with the '''Fo'''parameterized command line option.
This identifier is only defined in ALP mode.


Related Information:
===== @AlpMinor =====
The '''@AlpMinor''' identifier is a ''Text-EquateName'' that reflects the ''minor'' portion of the three-part assembler version number. It is padded on the right with zeros to allow minor version number comparisions independant of the major version and revisions numbers. See @AlpVersion for more information.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00052.htm|Fo - Produce Object File]] <br />
This identifier is only defined in ALP mode.


===== @AlpRevision =====
The '''@AlpRevision''' identifier is a ''Text-EquateName'' that reflects the ''revision'' portion of the three-part assembler version number. It allows revision number comparisions independant of the major and minor version numbers. See @AlpVersion for more information.


=== SourceNAME ===
This identifier is only defined in ALP mode.


This variable contains the name of the top-level source file currently being processed by the assembler; its contents appear exactly as the user typed it on the command line. Other internal variables derive their contents from this value.
===== @AlpVersion =====
The '''@AlpVersion''' identifier is a ''Text-EquateName'' that reflects the full three-part assembler version number. This is an encoding of the version number printed in the program banner when the assembler is invoked. This number and its requisite parts may be tested to determine the presence or absence of features provided by the assembler.


Related Information:
The assembler version number consists of three parts:
# The major version number (one digit)
# The minor version number (two digits)
# The revision number (three digits)


�[[00039.htm|File Names]] <br />
In the assembler banner, the numbers are separated by the period (.) character; the period is removed from the text defined by the predefined identifiers.


=== SrcDIR ===
For example, if the major version number is '''1''', the minor version number is '''2''', and the revision number is '''3''', then the full version number is printed in the assembler banner as '''1.02.003''', and the various predefined version identifers would be set as follows:
@AlpVersion  102003
@AlpMajor    100000
@AlpMinor      2000
@AlpRevision    003
This identifier is only defined in ALP mode.


This variable is derived from [[00021.htm|SourceNAME]]and reflects any drive or path information contained therein. For instance, if the value of [[00021.htm|SourceNAME]]is &quot;D:\Source\Dump\DumpMain.asm&quot;, then the value of '''SrcDIR'''would be &quot;D:\Source \Dump\&quot;. If no drive or path information was specified in the file name, then '''SrcDIR'''will contain the empty string.
===== @Cpu =====
The '''@Cpu''' identifier is a ''Numeric-EquateName'' that reflects the currently selected processor for which ALP is assembling instructions. This value is affected by issuing a ''Processor-Control-Directive'', and is a bit map that indicates the currently active processor instruction set(s).
{|class="wikitable"
!B!!A!!9!!8!!7!!6!!5!!4!!3!!2!!1!!0!!BIT SET IF ASSEMBLING FOR
|-
| || || || || || || || || || || ||1||8086/8088
|-
| || || || || || || || || || ||1|| ||80186
|-
| || || || || || || || || ||1|| || ||80286
|-
| || || || || || || || ||1|| || || ||80386
|-
| || || || || || || ||1|| || || || ||80486
|-
| || || || || || ||1|| || || || || ||80586 (Pentium)
|-
| || || || || ||1|| || || || || || ||80686 (Pentium Pro)
|-
| || || || ||1|| || || || || || || ||Privileged mode
|-
| || || ||1|| || || || || || || || ||8087
|-
| || ||1|| || || || || || || || || ||MMX Extensions
|-
| ||1|| || || || || || || || || || ||80287
|-
|1|| || || || || || || || || || || ||80387
|}


Related Information:
===== @Version =====
The '''@Version''' identifier is a ''Text-EquateName'' that reflects the MASM-compatible version number. The current emulation mode of the assembler affects the value of this symbol as follows:
: M510 510
: M600 600
: ALP 4294967295 (the highest possible value for an unsigned 32-bit integer)


�[[00039.htm|File Names]] <br />
==== Date and Time Information ====
These identifiers allow the programmer to query the system date or time during the assembly. Each time they are referenced, a new system request for the current date and time is made and the values held in the identifiers are refreshed.


===== @Date =====
The '''@Date''' identifier is a ''Text-EquateName'' that is set to the current system date. If the current operating mode is M600, the date is returned in the MM/DD/YY format. In native ALP mode, the date is returned in the MM/DD/YYYY format.


=== SrcEXT ===
The '''@Date''' identifier is not available in M510 mode.


This variable contains the default source file name extension that is conditionally appended to the concatenated values of [[00022.htm|SrcDIR]]and [[00024.htm|SrcNAME]]; the assembler treats the resulting string as the fully qualified input file name. The default value for '''SrcEXT'''is &quot;.asm&quot; unless altered by use of the '''Fes'''parameterized command line option.
===== @Time =====
The '''@Time''' identifier is a ''Text-EquateName'' that is set to the current system time in 24-hour HH:MM:SS format.


Related Information:
The '''@Time''' identifier is not available in M510 mode.


�[[00036.htm|Options]] <br />�[[00039.htm|File Names]] <br />�[[00062.htm|Fes - Control Source File Extension (SrcEXT)]] <br />
==== File Information ====
These identifiers return information about the file(s) being assembled.


===== @FileName =====
The '''@FileName''' identifier is a ''Text-EquateName'' that is set to the base name of the main file being assembled (as it appears on the command line).


=== SrcNAME ===
===== @Line =====
The '''@Line''' identifier is a ''Numeric-EquateName'' that is set to the current source line number in the file currently being assembled.


This variable contains the &quot;root file name&quot; portion of the source file name , which is extracted from the contents of the [[00021.htm|SourceNAME]]variable. For instance, if the value of [[00021.htm|SourceNAME]]is &quot;D:\Source\Dump\DumpMain.asm&quot;, then the value of '''SrcNAME'''would be &quot;DumpMain&quot;. '''SrcNAME'''should never contain the empty string unless the input file name was incorrectly specified; in which case the assembler will generate an error when it tries to access the file.
The '''@Line''' identifier is not available in M510 mode.


Related Information:
=== Literals ===
;Description
'''''Literals''''' are the notational method whereby numeric values or strings of character data are represented in the source stream. Literals are also commonly referred to as '''''constants''''' (especially in the context of high level languages) because they typically represent objects whose values do not change throughout the life of the assembly or compilation. However, literals should not be confused with run-time "constants"; ("read-only"; data items allocated by the programmer); they are assembly-time tokens used by the assembler to represent numeric values or character strings.


�[[00039.htm|File Names]] <br />
;Syntax
''Literal:''
: ''Floating-Point-Literal''
: ''Integer-Literal''
: ''String-Literal''


==== Integer Literals ====
;Description
An '''''integer literal''''' represents a fixed-point numeric value. An integer literal must begin with one of the numeric digits 0 - 9, and may be optionally terminated with a suffix character called a '''''radix specifier'''''. The radix specifier tells the assembler whether the literal is to be interpreted as a base 2 (binary), 8 (octal), 10 (decimal), or 16 ( hexadecimal) number. If the literal is not suffixed with a radix specifier , the assembler uses the value of the current radix to determine the base of the number. The default radix is 10 (decimal), but the '''''.RADIX''''' directive can be used to specify an alternate radix.


=== Using ALP ===
;Syntax
''Integer-Literal:''
: ''Binary-Integer-Literal''
: ''Octal-Integer-Literal''
: ''Decimal-Integer-Literal''
: ''Hexadecimal-Integer-Literal''


This chapter tells you how to:
===== Binary Integer Literals =====
;Syntax
''Binary-Integer-Literal:''
: ''Unqualified-Binary-Integer-Literal''
: ''Qualified-Binary-Integer-Literal''


1.Invoke and use ALP <br /> 2.Use environment variables to pass information to ALP <br />
''Unqualified-Binary-Integer-Literal:''
: ''Binary-Digit''
: ''Binary-Integer-Literal Binary-Digit''


''Qualified-Binary-Integer-Literal:''
: ''Unqualified-Binary-Integer-Literal Binary-Radix''


=== Invoking ALP ===
''Binary-Digit:''
: '''0'''
: '''1'''


To invoke ALP from the command line, type: <br />
''Binary-Radix:''
: '''b'''
: '''B'''
: '''y'''
: '''Y'''


<pre>alp </pre>
;Description
You can also invoke ALP by absolute reference from a makefile or command file; to do this, the directory should be among those referenced by the [[00033.htm|PATH]]environment variable.
A base-2 number containing either of the digits '''''0''''' and '''''1'''''.


=== Using Environment Variables ===
;Examples
The following are examples of unqualified binary integer literals:
10101
0
000001
1111000010101010


This section describes the environment variables that you can set and that are used by ALP.
The following are examples of qualified binary integer literals:
00001111b
1111Y
00y
1111000010101010B


===== Octal Integer Literals =====
;Syntax
''Octal-Integer-Literal:''
: ''Unqualified-Octal-Integer-Literal''
: ''Qualified-Octal-Integer-Literal''


=== _INCLUDE ===
''Unqualified-Octal-Integer-Literal:''
: ''Octal-Digit''
: ''Octal-Integer-Literal Octal-Digit''


When ALP processes an '''INCLUDE'''directive, ALP translates the value of the [[00008.htm|BaseEXE]]internal variable to uppercase and uses this value to construct the name of an ALP-specific environment variable having the form: <br />
''Qualified-Octal-Integer-Literal:''
: ''Unqualified-Octal-Integer-Literal Octal-Radix''


<pre>&lt; BaseEXE &gt; _ INCLUDE </pre>
''Octal-Digit:'' one of:
For example, If the value of [[00008.htm|BaseEXE]]is ''alp'', then ALP constructs an environment variable called '''ALP_INCLUDE'''and tries to locate it in the environment. If found, its contents would be expected to contain a list of directories in a format identical to that of the standard [[00032.htm|INCLUDE]] environment variable.
0 1 2 3 4 5 6 7


''Octal-Radix:''
: '''o'''
: '''O'''
: '''q'''
: '''Q'''


=== _OPTIONS ===
;Description
A base-8 number containing any of the digits '''''0''''' through '''''7'''''.


ALP translates the value of the [[00008.htm|BaseEXE]]internal variable to uppercase and uses this value to construct the name of an ALP-specific environment variable having the form: <br />
;Examples
The following are examples of unqualified octal integer literals:
01234567
27
765


<pre>&lt; BaseEXE &gt; _ OPTIONS </pre>
The following are examples of qualified octal integer literals:
For example, if the value of [[00008.htm|BaseEXE]]is ''alp'', then ALP constructs an environment variable called '''ALP_OPTIONS'''and tries to locate it in the environment. If found, its contents are logically prepended to the assembler command line.
27q
013o
567O
01234567Q


You can use this variable to set alternate default values for assembler command line options. For maximum flexibility, it is recommended that this variable contain a reference to a command line response file using an '''@ Filename'''directive, which allows the default command line options to be stored in a file rather than in the environment variable itself.
===== Decimal Integer Literals =====
;Syntax
''Decimal-Integer-Literal:''
: ''Unqualified-Decimal-Integer-Literal''
: ''Qualified-Decimal-Integer-Literal''


=== _PATH ===
''Unqualified-Decimal-Integer-Literal:''
: ''Decimal-Digit''
: ''Decimal-Integer-Literal Decimal-Digit''


Whenever ALP needs to search for one of its own component files (such as the messages file), the value of the [[00008.htm|BaseEXE]]internal variable is translated to uppercase and is used to construct the name of an ALP specific environment variable having the form &quot;&lt;[[00008.htm|BaseEXE]]&gt;'''_PATH'''.&quot; For example, if the value of [[00008.htm|BaseEXE]]is &quot;alp,&quot; then an environment variable called '''ALP_PATH'''would be constructed and an attempt would be made to locate it in the environment. If found, its contents would be expected to contain a list of directories in a format identical to that of the standard [[00033.htm|PATH]] environment variable. ALP then searches this list of paths when attempting to locate the component file.
''Qualified-Decimal-Integer-Literal:''
: ''Unqualified-Decimal-Integer-Literal Decimal-Radix''


=== DPATH ===
''Decimal-Digit:'' one of:
0 1 2 3 4 5 6 7 8 9


The '''DPATH'''environment variable may be utilized for the same purposes as the [[00030.htm|&lt;BaseEXE&gt;_PATH]]internal variable if so desired.
''Decimal-Radix:''
: '''d'''
: '''D'''
: '''t'''
: '''T'''


=== INCLUDE ===
;Description
A base-10 number containing any of the digits '''''0''''' through '''''9'''''.


The '''INCLUDE'''environment variable may be utilized for the same purposes as the [[00028.htm|&lt;BaseEXE&gt;_INCLUDE]]internal variable if so desired.
;Examples
The following are examples of unqualified decimal integer literals:
0123456789
19
090


The following are examples of qualified decimal integer literals:
01d
89t
4567D
0123456789T


=== PATH ===
===== Hexadecimal Integer Literals =====
;Syntax
''Hexadecimal-Integer-Literal:''
: ''Unqualified-Hexadecimal-Integer-Literal''
: ''Qualified-Hexadecimal-Integer-Literal''


The '''PATH'''environment variable may be utilized for the same purposes as the [[00030.htm|&lt;BaseEXE&gt;_PATH]]internal variable if so desired.
''Unqualified-Hexadecimal-Integer-Literal:''
: ''Decimal-Digit''
: ''Hexadecimal-Integer-Literal Decimal-Digit''
: ''Hexadecimal-Integer-Literal Hexadecimal-Digit''


=== Using the Command Line ===
''Qualified-Hexadecimal-Integer-Literal:''
: ''Unqualified-Hexadecimal-Integer-Literal Hexadecimal-Radix''


This section describes command line parameter types, syntax, and options.
''Decimal-Digit:'' one of:
0 1 2 3 4 5 6 7 8 9


=== Command Line Parameter Types ===
''Hexadecimal-Digit:'' one of:
a b c d e f
A B C D E F


Command line '''''parameters''are individual &quot;words,&quot; or patterns of characters separated by white space. Each individual parameter is recognized by the command line lexical analyzer as having a certain &quot;pattern,&quot; and is thus assigned a '''''parameter type'', as described in the following sections. Parameters should be separated by one or more blanks, tabs, or (when reading from a response file) new line characters, and double quotation marks may be used on the command line to remove the special meaning from the operating system metacharacters. Although the host operating system may support the enclosing of command line parameters within double quotes ( &quot;&quot;) (known as &quot;quoting&quot;), the ALP command line parser also performs quote interpretation. This is necessary to properly interpret quoted parameters within '''@Filename'''response files, for which there is no built-in support provided by the default operating system command shell.''''''
''Hexadecimal-Radix:''
: '''h'''
: '''H'''


Parameter types are determined by looking at the first character of each individual &quot;word.&quot; Options begin with a plus (+) or minus (-), and file names begin with any other legal file name character (as dictated by the operating system). A special case is a word beginning with the ''at sign''(@) character, which signifies the beginning of the '''@Filename'''(read from a response file) directive.
;Description
A base-16 number using any combination of the digits '''0''' through '''9''' and the lowercase letters '''a''' through '''f''' or the uppercase letters '''A''' through '''F'''. The lowercase and uppercase representations of any given hexadecimal letter are equivalent.


;Constraints
A hexadecimal integer literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the '''0''' digit.


=== Options ===
;Examples
The following are examples of unqualified hexadecimal integer literals:
01BD
9A
0AB


Options appear on the command line as mnemonic identifiers prefixed by either of the plus (+) or minus (-) characters, and must be separated from other command line parameters by at least one blank character. Case is not significant in option identifiers.
The following are examples of qualified hexadecimal integer literals:
1234ABCDh
01DH
0bh
1111FFFFH


A single option may be specified more than once on the command line within a given scope; the last occurrence overrides all previous definitions within that scope unless the effect of the option is to collect information in a cumulative fashion. Options are not cumulative unless documented otherwise on an individual basis.
==== Floating-Point Literals ====
;Description
A '''floating-point literal''' is a notation for representing real numbers. The assembler provides both decimal and hexadecimal floating-point notations for representing real numbers.


There are two forms of options:
;Syntax
''Floating-Point-Literal:''
: ''Decimal-Floating-Point-Literal''
: ''Hexadecimal-Floating-Point-Literal''


�[[00037.htm|Switch Option]] <br />�[[00038.htm|Parameterized Option]] <br />
===== Decimal Floating-Point Literals =====
;Syntax


Some options may actually combine both functions of the ''switched''and ''parameterized''variations; for instance, the '''+Fl'''switch option &quot;turns on&quot; the creation of a listing file, while a parameterized option of the same name (for example, '''+Fl:george.lst''') has the same effect, but also treats the argument field as the name of the listing file to create.
''Decimal-Floating-Point-Literal:''<br />''Significand-Part''<br />''Significand-Part Exponent-Part''<br /><br />''Significand-Part:''<br />''Digit-Sequence'''''.'''''Digit-Sequence''<br />''Digit-Sequence'''''.'''<br /><br />''Exponent-Part:''<br />''E-Character Digit-Sequence''<br />''E-Character Sign Digit-Sequence''<br /><br />''E-Character:''<br />'''e'''<br />'''E'''<br /><br />''Sign:''<br />'''-'''<br />'''+'''<br /><br />''Digit-Sequence:''<br />''Digit''<br />''Digit-Sequence Digit''<br /><br />''Digit:''one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />'''


=== Switch Option ===
;Description
A decimal floating-point literal has a ''significand part'' that may be followed by an ''exponent part''. The significand part consists of a digit sequence representing the whole-number part, followed by a period (.), followed by a digit sequence representing the fraction part. The exponent part consists of an introductory character ('''e'''or '''E'''), followed by an optional sign character ('''+'''or '''-'''), followed by a digit sequence representing the exponent.


'''''Switch Options''represent a Boolean value ('''on'''or '''off''', '''yes'''or '''no''', '''true'''or '''false''') for the identifier specified in the option. The plus (+) or minus ( -) character introducing the option specifies the value of the switch; &quot;+&quot; is equivalent to '''on''', '''yes''', or '''true'''; and &quot;-&quot; is equivalent to '''off''', '''no''', or '''false'''.'''
;Constraints
The introductory ''Digit-Sequence'' in the ''Significand-Part'' must be specified ( the literal cannot begin with a ".").


Because plus (+) is not a character traditionally used to introduce a command line option, ALP provides an alternate method of specifying a switch option that resembles a more commonly used syntax. The character that affects the actual value of the &quot;switch&quot; (that is, the (+) or (-) character) may also be specified directly after the option identifier; in this case the option must still be introduced by either the (+) or (-) character, but the trailing &quot;switch value&quot; takes precedence.
;Examples
25.23
2.523E1
2523.0E-2


The following are examples of '''''Switch Options'': <br />'''
===== Hexadecimal Floating-Point Literals =====
;Syntax


<pre>
''Hexadecimal-Floating-Point-Literal:''<br />''Hexadecimal-Literal Float-Radix''<br /><br />''Hexadecimal-Literal:''<br />''Decimal-Digit''<br />''Hexadecimal-Literal Decimal-Digit''<br />''Hexadecimal-Literal Hexadecimal-Digit''<br /><br />''Decimal-Digit:''one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />'''<br />''Hexadecimal-Digit:''one of: '''<br />a b c d e f <br />A B C D E F <br />'''<br />''Float-Radix:''<br />'''r'''<br />'''R'''
+ ML
- ml +
+ Fl
- Fl - </pre>


=== Parameterized Option ===
;Description
A hexadecimal floating-point literal provides a means of initializing floating point values using a notation more closely tied to the internal machine representation than that of the ''Decimal-Floating-Point-Literal''. Such literals are coded in a fashion similar to that of a normal ''Hexadecimal-Integer-Literal'', but a different radix suffix is used to inform the assembler that the value is to be used in the allocation of real numbers rather than integers.


'''''Parameterized Options''are introduced in the same manner as switch options, but are instead followed by a colon (:) or an equals sign (=) (with no intervening blank space) to indicate that the option takes one or more '''''arguments''. The format of the argument field is option specific.''''''
;Constraints
A hexadecimal floating-point literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the '''''0''''' digit.


Using the plus (+) character versus the minus (-) character to introduce a parameterized option may or may not have an effect upon how the option is interpreted. Refer to the description of each individual option for details.
The literal must specify the correct number of hexadecimal digits according to the size of the real-number data-type to which it will be assigned. For '''REAL4''', '''REAL8''', and '''REAL10''' variables, the respective number of digits in the literal must be 8, 16, and 20. For literals encoded with a leading zero, the respective number of digits must be 9, 17, and 21.


The following are examples of '''''Parameterized Options'': <br />'''
;Examples
3F800000r


<pre>
==== String Literals ====
- Fl = Zappa . lst
;Syntax
- Sv : M510
+ fo = &quot; \ obj \ dd \ driver . obj &quot;
- m : 127 - </pre>


=== File Names ===
''String-Literal:''<br />''D-String''<br />''S-String''<br /><br />''D-String:''<br />''D-Quote D-Quote''<br />''D-Quote D-Char-Sequence D-Quote''<br /><br />''S-String:''<br />''S-Quote S-Quote''<br />''S-Quote S-Char-Sequence S-Quote''<br /><br />''D-Char-Sequence:''<br />any printable character except ''D-Quote''<br />''D-Quote D-Quote''<br /><br />''S-Char-Sequence:''<br />any printable character except ''S-Quote''<br />''S-Quote S-Quote''<br /><br />''D-Quote:''<br />'''"'''<br /><br />''S-Quote:''


A file name may be used as an argument to certain command line options or as a stand-alone command line parameter. The file name character set and naming conventions are operating system dependent, and are treated as transparently as possible by ALP. The use of operating system metacharacters in file names should be avoided, and file names should not begin with the plus (+) or minus (-) characters.
;Description
A '''string literal''' contains a sequence of zero or more characters enclosed in quotation mark symbols. Either a single (') or double (") quotation mark symbol may be used as the '''quote character''' that opens and closes the string literal. If a single quotation mark symbol is used as the quote character, then double quotation mark symbols may appear as data characters within the string literal, and vice versa. If the quote character must also appear as a character within the string literal, use two adjacent quote characters; this will allow a single occurrence of the quote character to be inserted into the string literal.


Any file name may be &quot;qualified&quot; with drive or path information as appropriate for the host operating system. ALP accepts both the forward slash (/) and the backward slash (\) as legal path name characters, as well as the colon (:) character. Care must be exercised however, because the underlying operating system may reject the usage of some of these characters.
A quote character must be used to terminate the string literal before the end of the line is reached, otherwise an error message is issued and the literal is terminated by the end of line character. A string literal may span multiple lines only if a backslash (\) appears as the last non- whitespace character on the line, in which case the backslash, all surrounding whitespace characters, and the end of line character are deleted and the literal is continued with the first character on the next line.


;Examples
'Hello, world'
"That's the way it is"
'Unless it''s not'
"SuperStringCon \
catenated"


=== Command Line Syntax ===
=== Punctuators ===
;Description
Punctuators are used as operators and separator characters.


<br />
;Syntax
''Punctuator:''one of '''<br />[ ] ( ) { } * , : = ; %'''


<pre>/-------------------------------------------------------------------------------\
== Declarations ==
|                                                                              |
A '''''Type Declaration''''' is a language construct that specifies the characteristics of code and data objects used in a program.
|                                                  /----------------------\    |
|                                                  |                      |    |
| &gt;&gt;--ALP-------------------------------------------FileName File Options----&gt;&lt; |
|          \-Global Options-/  \-Group Options-/                                |
|                                                                              |
\-------------------------------------------------------------------------------/</pre>


=== Type Declarations ===
;Description
A ''Type-Declaration'' is a common construct used in various assembler directives to establish type attribute information for a program object. A ''Type-Declaration'' is needed to determine the data type of a variable or labeled address. The [[#TYPEDEF|TYPEDEF]] directive offers a method of assigning a name to a ''Type-Declaration''.


The assembler accepts one or more file names for processing. Each file name is taken to be the name of a source file to assemble; file names are not interpreted according to their file &quot;type&quot; or extension to determine if they are valid input files.
;Syntax
''Type-Declaration:''
:''TypeName''
:''TypeName Array-Spec''
:''Pointer-Spec''
:''Pointer-Spec TypeName''
:''Pointer-Spec TypeName Array-Spec''


The OS/2 version of the assembler is enabled to accept ''wild-card characters'' (? and *) in file names, which emulates the UNIX ability to expand a single file name specification into a list of all files that match the wild -card pattern. The '''?'''character matches any single file name character in the given position, and the '''*'''character matches any number of file name characters.
''Pointer-Spec:''
:'''PTR'''
:''[[#Distance-TypeName|Distance-TypeName]]'' '''PTR'''
:''Pointer-Spec Array-Spec''


''Array-Spec:''
:'''[''' ''Expression'' ''']'''
:''Array-Spec'' '''[''' ''Expression'' ''']'''


=== Global Options ===
''TypeName:''
:''Distance-TypeName''
:''Scalar-TypeName''
:''UserDefined-TypeName''


Command line options fall into this category only if they apply to the assembler executable itself and not to any specified files. Options that request the display of assembler help messages fall into this category, as well as the option that controls display of the assembler banner.
;Examples


=== Group Options ===
The '''TYPEDEF''' directive is used to illustrate the type declaration syntax:
<pre>
CHAR        typedef  byte              ;  Alias of intrinsic TypeName
PBYTE      typedef  ptr  byte          ;  Pointer to intrinsic TypeName
PCHAR      typedef  ptr  CHAR          ;  Pointer to TypeDef-TypeName
PPCHAR      typedef  ptr  PCHAR        ;  Pointer to a pointer to a CHAR
PPBYTE      typedef  ptr  ptr byte      ;  Similar to PPCHAR
PVOID      typedef  ptr                ;  Pointer to nothing (pointer to code)
PCODE      typedef  ptr  PROC          ;  Similar to PVOID
PFCODE      typedef  far  ptr far      ;  Far pointer to far code address


Command line options fall into this category if the settings they control can be applied to a list of multiple files within a given scope without causing ambiguities. Group options are useful for such operations as:
; vector declarations


�Requesting a listing file be generated for all files within the group <br />�Specifying the target directory for all generated object files <br />�Controlling the display of warning and informational messages for all files within the group <br />
ACHAR      typedef  CHAR[16]          ;  Array of 16 characters
AAWORD      typedef  word[2][2]        ;  multi-dimensional array
APBYTE      typedef  ptr[8] byte      ;  Array of 8 pointers to byte
APACHAR    typedef  ptr[4] ACHAR      ;  Array of 4 ptrs to arrays of 16 chars


Within a given scope (see [[00044.htm|Command Line Scope Operator ()]]) the command line parser assigns the ''group''classification to each option until the first source file name is encountered; group option settings are applied to all file names that follow within a given scope. After encountering the first source file name, options are assigned the ''file''classification.
SIZES_T    struct                    ;   define an intrinsic structure type
  little  byte      ?
  Medium  word      ?
  BIG      dword    ?
SIZES_T    ends


[[[00042.htm|prev]]][[[00044.htm|next]]][[[00040.htm|parent]]][[[toc.htm|TOC]]]<br />
SIZES      typedef  SIZES_T          ;  alias for intrinsic structure type
PSIZES      typedef  ptr SIZES_T      ;  and a type to point to it


=== File Options ===
PFORWARD    typedef  ptr FORWARD      ;  Pointers to forward-referenced types
FORWARD    struct                    ;  are assumed to be pointers to structs
  blah      word    ?
FORWARD    ends
</pre>


All options appearing to the right of a file name within a given scope (see [[00044.htm|Command Line Scope Operator ()]]) are applied to that file only. File options take precedence over any settings inherited from previously encountered group options.
== Expressions ==
An expression is a sequence of ''operators'' and ''operands'' that are evaluated to derive a numeric result, an effective address, or a register operand.


It should be noted that file names specified using wild-card characters and used in combination with file options may not yield the expected result; the file options will be applied only to the last file in the resulting wild-card expansion file name list.
Expressions are specified using standard infix notation, which is recursive in nature, ie., expressions may be nested within other expressions. The evaluation of an expression occurs in a left to right manner, and is influenced by the rules of operator ''precedence'' and ''associativity''. The order in which expressions are evaluated can be controlled by grouping operands and operators together using parentheses ().


[[[00043.htm|prev]]][[[00045.htm|next]]][[[00040.htm|parent]]][[[toc.htm|TOC]]]<br />
=== Expression Syntax ===
;Description
This section describes the complete expression syntax.


=== Command Line Scope Operator () ===
;Syntax
''Expression:''
: ''Duplicative-Expression''


At any point on the command line, a new ''scope''may be opened using the scope operator (). The scope operator effectively creates a new logical command line whose contents are enclosed in parentheses and is parsed in isolation from other scopes. Any group options in effect at the time the new scope is opened are inherited and applied to all files named within.
''Duplicative-Expression:''
: ''Attribute-Expression''
: ''Attribute-Expression'' DUP '''(''' ''Initializer-List'' ''')'''


[[[00044.htm|prev]]][[[00046.htm|next]]][[[00034.htm|parent]]][[[toc.htm|TOC]]]<br />
''Attribute-Expression:''
: ''OR-Expression'' SHORT ''Additive-Expression''
: .TYPE ''OR-Expression''
: OPATTR ''OR-Expression''


=== Command Line Options ===
''OR-Expression:''
: ''AND-Expression''
: ''OR-Expression'' OR ''AND-Expression''
: ''OR-Expression'' XOR ''AND-Expression''


This section describes all the ALP command line options. For each option, a table appears in the description section with the following format: <br /><br />
''AND-Expression]]:''
: ''NOT-Expression'']]
: ''AND-Expression'']] AND ''NOT-Expression''


<pre>/-------------------------------------------------------------------------\
''NOT-Expression]]:''
|Type|Global|Group|File|Default                                          |
: ''Relational-Expression'' NOT ''Relational-Expression''
|----+------+-----+----+--------------------------------------------------|
|... |...  |...  |... |...                                              |
\-------------------------------------------------------------------------/</pre>
The values appearing in this table are defined as follows:


Type This field specifies the ''type''of the option described in that row, and can be one of:
''Relational-Expression:''
: ''Additive-Expression''
: ''Relational-Expression'' EQ ''Additive-Expression''
: ''Relational-Expression'' NE ''Additive-Expression''
: ''Relational-Expression'' GT ''Additive-Expression''
: ''Relational-Expression'' GE ''Additive-Expression''
: ''Relational-Expression'' LT ''Additive-Expression''
: ''Relational-Expression'' LE ''Additive-Expression''


'''S'''- [[00037.htm|Switch Option]] <br />'''P'''- [[00038.htm|Parameterized Option]]
''Additive-Expression:'
: ''Multiplicative-Expression''
: ''Additive-Expression'' + ''Multiplicative-Expression''
: ''Additive-Expression'' - ''Multiplicative-Expression''


Global Specifies whether or not the option is valid only in a '''''global'' context; that is, in the outermost scope on the command line. These options typically have meaning only for the assembler executable itself, and not for any files to be processed.'''
''Multiplicative-Expression:''
: ''Narrowed-Expression''
: ''Multiplicative-Expression'' * ''Narrowed-Expression''
: ''Multiplicative-Expression'' / ''Narrowed-Expression''
: ''Multiplicative-Expression'' MOD ''Narrowed-Expression''
: ''Multiplicative-Expression'' SHL ''Narrowed-Expression''
: ''Multiplicative-Expression'' SHR ''Narrowed-Expression''


Group Specifies whether or not the option is valid in a '''''group''context; that is, if the option may be applied to multiple files within a given scope without causing ambiguities.'''
''Narrowed-Expression:''
: ''Cast-Expression''  
: HIGH ''Cast-Expression''
: HIGHWORD ''Cast-Expression''
: LOW ''Cast-Expression''
: LOWWORD ''Cast-Expression''


File Specifies whether or not the option is valid only in a '''''file''context; that is, if the option may only be applied to a single file within a given scope.'''
''Cast-Expression:''
: ''Element-Selection-Expression''
: OFFSET ''Cast-Expression''
: SEG ''Cast-Expression''
: THIS ''Element-Selection-Expression''
: TYPE ''Element-Selection-Expression''
: ''Cast-Expression'' PTR ''Cast-Expression''
: ''Cast-Expression'' : ''Cast-Expression''


Default This field shows the default value for the option being described. <br />
''Element-Selection-Expression:''
: ''Sign-Expression''
: ''Element-Selection-Expression''
: ''Sign-Expression''
: ''Element-Selection-Expression'' . ''Sign-Expression''


[[[00045.htm|prev]]][[[00047.htm|next]]][[[00045.htm|parent]]][[[toc.htm|TOC]]]<br />
''Sign-Expression:''
: ''Primary-Expression''
: - ''Primary-Expression''
: + ''Primary-Expression''


=== Base Options ===
''Primary-Expression:''
: ''Literal-Operand''
: ''Record-Constant''
: ''Identifier-Operand''
: ''Register-Operand''
: ''Integral-TypeName-Operand''
: ''Value-Substitution-Operand''
: LENGTH ''Identifier-Operand''
: LENGTHOF ''Identifier-Operand''
: MASK ''Identifier-Operand''
: SIZE ''Element-Selection-Expression''
: SIZEOF ''Element-Selection-Expression''
: WIDTH ''Identifier-Operand''
: ''Parenthesized-Expression''
: ''Indirected-Expression''
: ''Compound-Initializer''


This section describes the standalone base options that are defined by a single unique mnemonic identifier character.
''Literal-Operand:''
: ''Floating-Point-Literal''
: ''Integer-Literal''
: ''String-Literal'']]


[[[00046.htm|prev]]][[[00048.htm|next]]][[[00046.htm|parent]]][[[toc.htm|TOC]]]<br />
''Record-Constant:''
: ''Identifier-Operand'' '''<''' ''Field-List'' '''>'''
: ''Identifier-Operand'' '''{''' ''Field-List'' '''}'''


=== D - Define Text Macro ===
''Field-List:''
: ''Attribute-Expression''
: ''Field-List'' ''',''' ''Attribute-Expression''


This option allows the definition of a symbolic identifier that becomes visible during the assembly of the input file. A single parameter must be specified using one of the following forms:
''Identifier-Operand:''
: ''Identifier''


<br />
''Register-Operand:''
: ''Processor-Register''


<pre>Name[=Value]</pre>
''Integral-TypeName-Operand:''
<br /><br />
: ''Scalar-TypeName''
: ''Distance-TypeName''


<pre>Name[:Value]</pre>
''Value-Substitution-Operand:''
<br />
: ''Anonymous-Label-Alias''
: ''Location-Counter-Alias''
: ''Indeterminate-Value-Alias''
: '''FLAT'''


The ''Name''entry must have the same lexical syntax as a normal assembler [[00149.htm|''Identifier'']]. The ''Name''entry is converted to a [[00157.htm|''Text-EquateName'']]before assembly begins. If no explicit value is specified for the name, then it is assigned the empty string. This is equivalent to specifying the following assembler statement: <br />
''Parenthesized-Expression:''
: '''(''' ''Attribute-Expression'' ''')'''


<pre>    Name  EQU  &lt; &gt; </pre>
''Indirected-Expression:''
If an explicit value is to be assigned, the ''Name''entry must be immediately followed by a colon (:) or equals sign (=) delimiter with no intervening spaces. Blank characters may be specified between the delimiter and the value field. The ''Value''field may contain any text data, but it must be enclosed in double quotes (&quot;&quot;) if it contains blanks, tabs, or operating system metacharacters (such as &amp; or |).
: '''[''' ''Attribute-Expression'' ''']'''


'''Note:'''If quotes are used to specify a value containing embedded blanks or tabs, then at least one blank is required between the delimiter (colon or equals sign) and the opening quote of the value field. For example: <br />
''Compound-Initializer:''
: '''<''' ''Initializer-List'' '''>'''
: '''{''' ''Initializer-List'' '''}'''


<pre>  - D : NAME =  &quot; This  string  will  be  correctly  interpreted &quot;
''Initializer-List:''
  - D : NAME = &quot; This  will  not ;  no  blank  after  the  equals  sign &quot; </pre>
: ''Duplicative-Expression''
<br />
: ''Initializer-List'' ''',''' ''Duplicative-Expression''


<pre>/-------------------------------------------------------------------------\
==== Duplicative Initialization Expression ====
|Type|Global|Group|File|Default                                          |
;Description
|----+------+-----+----+--------------------------------------------------|
A '''''Duplicative Initialization Expression''''' is one that can be optionally used during the initialization of variables such that the operand is duplicated a specified number of times.
|P  |Yes  |Yes  |Yes |(no default value)                                |
\-------------------------------------------------------------------------/</pre>
[[[00047.htm|prev]]][[[00049.htm|next]]][[[00046.htm|parent]]][[[toc.htm|TOC]]]<br />


=== I - Specify Include File Search Path ===
;Syntax


See [[00053.htm|Fdi - Specify Include File Search Path]].
''Duplicative-Expression:''
:''Attribute-Expression''
:''Attribute-Expression''
:[[#DUP]] '''(''' ''Initializer-List''' '')'''


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''Initializer-List:''
:''Duplicative-Expression''
:''Initializer-List'' ''',''' ''Duplicative-Expression''


=== File Control Options ===
===== Duplicative Initialization (DUP Operator) =====
;Description
The '''DUP''' operator creates a ''Duplicated-ExpressionType'' from the ''Initializer-List'' enclosed in parentheses. This construct can be used to create arrays of information during data allocation.


All options that perform file or file name manipulation are described in this section. File Control Options begin with the letter '''&quot;F&quot;''', and the last letter of the option identifier specifies the type of file or file name to which the option applies as follows:
;Syntax


'''i'''Include File <br />'''l'''Listing File <br />'''m'''Messages File <br />'''o'''Object File <br />'''s'''Source File <br />
''Attribute-Expression'' '''DUP ('''''Initializer-List''''')'''
''Initializer-List:''
''Duplicative-Expression''
''Initializer-List''''','''|''Duplicative-Expression''


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;Constraints


=== Fl - Produce Listing File ===
The left hand operand of the '''DUP''' operator must evaluate to an ''Absolute-ExpressionType''.


Turn this flag on to produce an assembler listing file. Using the parameterized version of the option allows the listing file to be explicitly named.
Each ''Duplicative-Expression'' in the ''Initializer-List'' must evaluate to an ''Initializer-ExpressionType''.


Only this option controls the actual creation of a listing file; [[00063.htm|Listing Control Options]]have no effect if this option has not been turned on.
;Examples
STR  STRUCT
  One  BYTE  0
  Two  BYTE  0
STR  ENDS


<br />
Array1  WORD 4 DUP (1,2,3,4)        ; allocates 16 words
Array2  STR  8 DUP (<1,2>)          ; 8 structures


<pre>/-------------------------------------------------------------------------\
==== Attribute Expression ====
|Type|Global|Group|File|Default                                          |
;Description
|----+------+-----+----+--------------------------------------------------|
An '''Attribute Expression''' is one that optionally extracts or modifies one or more of the basic properties of its operand.
|S  |Yes  |Yes  |Yes |-Fl (no listing file is generated)                |
|----+------+-----+----+--------------------------------------------------|
|P  |No    |No  |Yes |-Fl:&lt;LstDIR&gt;&lt;LstNAME&gt;[&lt;LstEXT&gt;]                  |
|    |      |    |    |(A listing file name is generated using the values|
|    |      |    |    |of the referenced internal variables.  The LstEXT |
|    |      |    |    |extension is appended if this feature is turned  |
|    |      |    |    |on.)                                              |
\-------------------------------------------------------------------------/</pre>
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=== Fm - Produce Messages File ===
;Syntax
''Attribute-Expression:''
: ''OR-Expression''
: SHORT ''Additive-Expression''
: .TYPE ''OR-Expression''
: OPATTR ''OR-Expression''


Turn this flag on to produce a messages file. Using the parameterized version of the option allows the messages file to be explicitly named.
===== Expression Descriptor Bitmap (.TYPE Operator) =====
;Description
The '''.TYPE''' operator is considered obsolete. The [[#OPATTR]] operator should be used instead.


Within the context of a given assembly, by default all error, warning, and informational messages are printed to the standard output device. Use of the '''Fm'''option allows these messages to be redirected to a separate file; this can be useful when dissecting the output from multiple assemblies. Messages with a severity greater than '''Error'''are printed to the standard error device, and do not appear in the messages file.
The '''.TYPE''' operator returns a byte value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table:
{|class="wikitable"
!7!!6!!5!!4!!3!!2!!1!!0!!BIT SET IF EXPRESSION
|-
| || || || || || || ||1||Is a Direct-ExpressionType
|-
| || || || || || ||1|| ||Is a Indirect-ExpressionType, an Indexed-ExpressionType, or a combination of both
|-
| || || || || ||1|| || ||Is an Immediate-ExpressionType
|-
| || || || ||1|| || || ||Is an Indirect-ExpressionType
|-
| || || ||1|| || || || ||Is a Register-ExpressionType
|-
| || ||1|| || || || || ||Was parsed and evaluated without error (no undefined symbols, etc.)
|-
| ||1|| || || || || || ||Is relative to the SS Segment-Register
|-
|1|| || || || || || || ||Contains an External Reference
|}


<br />
.TYPE OR-Expression


<pre>/-------------------------------------------------------------------------\
;Syntax
|Type|Global|Group|File|Default                                          |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Fm (no messages file is generated; all messages  |
|    |      |    |    |are printed on the standard output)              |
|----+------+-----+----+--------------------------------------------------|
|P  |No    |No  |Yes |-Fm:&lt;MsgDIR&gt;&lt;MsgNAME&gt;[&lt;MsgEXT&gt;]                  |
|    |      |    |    |(A messages file name is generated using the      |
|    |      |    |    |values of the referenced internal variables.  The |
|    |      |    |    |MsgEXT extension is appended if this feature is  |
|    |      |    |    |turned on.)                                      |
\-------------------------------------------------------------------------/</pre>
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=== Fo - Produce Object File ===
'''.TYPE''' ''OR-Expression''


An object file name is generated using the values of the referenced internal variables. The [[00019.htm|ObjEXT]]extension is appended if this feature is turned on.
;Examples


By default, this switch is turned on and thus an object file is produced ( provided the assembly completes without errors); this switch may be turned off if an object file is not desired. Using the parameterized version of the option allows the object file to be explicitly named.
BumpCounter macro bump
  if (((.TYPE (bump)) and 07h) eq 04h)
      Counter = Counter + bump
  else
      .err <Non-constant value passed to BumpCounter>
  endif
endm


<br />
===== Extended Descriptor Bitmap (OPATTR Operator) =====
OPATTR OR-Expression


<pre>/-------------------------------------------------------------------------\
;Syntax
|Type|Global|Group|File|Default                                          |
'''OPATTR''' ''OR-Expression'
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Fo (an object file is generated)                |
|----+------+-----+----+--------------------------------------------------|
|P  |No    |No  |Yes |-Fo:&lt;ObjDIR&gt;&lt;ObjNAME&gt;[&lt;ObjEXT&gt;]                  |
\-------------------------------------------------------------------------/</pre>
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=== Fdi - Specify Include File Search Path ===
;Description


This option accepts a path (or list of paths separated by semicolons) that are searched by the assembler while attempting to locate an '''INCLUDE'''file. When multiple occurrences of this option are specified within a given scope , the effect is cumulative rather than destructive; successive occurrences add to the existing list rather than overwriting previous definitions. The more conventional spelling &quot;'''I'''&quot; can be used as an alias for the '''Fdi'''option.
The '''OPATTR''' operator returns a superset of the information returned by the .TYPE operator, which should be considered obsolete.


<br />
The '''OPATTR''' operator returns a word value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table:
{|class="wikitable"
!A98
!7
!6
!5
!4
!3
!2
!1
!0
!BIT SET IF EXPRESSION
|-
|
|
|
|
|
|
|
|
|1
|Is a Direct-ExpressionType
|-
|
|
|
|
|
|
|
|1
|
|Is a Indirect-ExpressionType, an Indexed-ExpressionType, or a combination of both
|-
|
|
|
|
|
|
|1
|
|
|Is an Immediate-ExpressionType
|-
|
|
|
|
|
|1
|
|
|
|Is an Indirect-ExpressionType
|-
|
|
|
|
|1
|
|
|
|
|Is a Register-ExpressionType
|-
|
|
|
|1
|
|
|
|
|
|Was parsed and evaluated without error (no undefined symbols, etc.)
|-
|
|
|1
|
|
|
|
|
|
|Is relative to the SS Segment-Register
|-
|
|1
|
|
|
|
|
|
|
|Contains an External Reference
|-
|LLL
|
|
|
|
|
|
|
|
|Language encoding (described below)
|}


<pre>/-------------------------------------------------------------------------\
The '''LLL''' field (bits 8, 9, and A) comprise an enumerated value that describes the language attribute assigned to the expression as follows:
|Type|Global|Group|File|Default                                          |
* 000 No language attribute used in expression
|----+------+-----+----+--------------------------------------------------|
* 001 C
|P  |Yes  |Yes  |Yes |-Fdi:&lt;IncDIR&gt;                                    |
* 010 SYSCALL
\-------------------------------------------------------------------------/</pre>
* 011 STDCALL
[[[00053.htm|prev]]][[[00055.htm|next]]][[[00049.htm|parent]]][[[toc.htm|TOC]]]<br />
* 100 PASCAL
* 101 FORTRAN
* 110 BASIC
* 111 OPTLINK


=== Fdl - Directory to Store Listing File (LstDIR) ===
;Constraints
This operator is not available in M510 mode.


This option affects the [[00012.htm|LstDIR]]variable and allows the user to specify a target directory where the listing file(s) will be stored; by default this variable is empty and listing file(s) are created in the current working directory. This value is ignored if the '''Fl'''option was used to explicitly name the listing file, and the name included absolute or relative path information.
;Examples
L_MASK    equ 011100000000y              ; mask to isolate language bits
L_OPTLINK  equ 011100000000y              ; setting for OptLink calling convention
VerifyCallBack  macro  ProcName
  if (((OPATTR (ProcName)) and L_MASK) ne L_OPTLINK)
      .err <Call-back routine must have OptLink linkage>
  endif
endm


If the value specified in this option is anything other than an unadorned '''''drive letter''(for example, '''D:''') or a string ending with a '''''path separator character''('''/'''or '''\'''), then the '''''path separator character''appropriate for the underlying operating system is appended to the string.'''''''''
===== Force Short Relative Address (SHORT Operator) =====
;Syntax
'''SHORT''' ''Additive-Expression''


<br />
;Description


<pre>/-------------------------------------------------------------------------\
The '''SHORT''' operator forces the assembler to calculate the distance from the start of the next instruction to the target specified by the operand (given by ''Additive-Expression'') to be less than 128 bytes away. This can cause the assembler to generate more efficient control transfer instructions when the target is a forward reference. By default, the assembler assumes that the code-relative target is of '''NEAR''' distance when the target is an unqualified forward reference.
|Type|Global|Group|File|Default                                          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Fdl:&lt;LstDIR&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Fdm - Directory to Store Messages File (MsgDIR) ===
;Constraints
The ''Additive-Expression'' must evaluate to a ''Direct-ExpressionType''.


This option affects the [[00015.htm|MsgDIR]]variable and allows the user to specify a target directory where the messages file(s) will be stored; by default this variable is empty and messages file(s) are created in the current working directory. This value is ignored if the '''Fm'''option was used to explicitly name the message file, and the name included absolute or relative path information.
;Examples
  JMP    Forward                ; target unknown, NEAR jump generated
  JMP    SHORT Forward          ; force SHORT encoding
  .
  .                      ; fewer than 128 bytes of instructions
  .
Forward:                ; definition of target


If the value specified in this option is anything other than an unadorned '''''drive letter''(for example, '''D:''') or a string ending with a '''''path separator character''('''/'''or '''\'''), then the '''''path separator character''appropriate for the underlying operating system is appended to the string.'''''''''
==== Bitwise OR Expression ====
;Description
A '''Bitwise OR Expression''' is one where an optional binary bitwise '''OR''' operation between the left and right operands is performed and the result returned.


<br />
;Syntax
''OR-Expression:'' ''AND-Expression''
''OR-Expression'' OR ''AND-Expression''
''OR-Expression'' XOR ''AND-Expression''


<pre>/-------------------------------------------------------------------------\
===== Bitwise Inclusive OR (OR Operator) =====
|Type|Global|Group|File|Default                                          |
;Syntax
|----+------+-----+----+--------------------------------------------------|
''OR-Expression'' '''OR''' ''AND-Expression''
|P  |Yes  |Yes  |Yes |-Fdm:&lt;MsgDIR&gt;                                     |
\-------------------------------------------------------------------------/</pre>
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=== Fdo - Directory to Store Object File (ObjDIR) ===
;Description
The '''OR''' operator performs a binary bitwise OR operation on the left and right hand operands.


This option affects the [[00018.htm|ObjDIR]]variable and allows the user to specify a target directory where the object file(s) will be stored; by default this variable is empty and object file(s) are created in the current working directory. This value is ignored if the '''Fo'''option was used to explicitly name the object file, and the name included absolute or relative path information.
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


If the value specified in this option is anything other than an unadorned '''''drive letter''(for example, '''D:''') or a string ending with a '''''path separator character''('''/'''or '''\'''), then the '''''path separator character''appropriate for the underlying operating system is appended to the string.'''''''''
;Examples
One  EQU  1
Two  EQU  2
MOV  AX, One OR Two        ; moves 3 into AX


<br />
===== Bitwise Exclusive OR (XOR Operator) =====
;Syntax
''OR-Expression'' '''XOR''' ''AND-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''XOR''' operator performs a binary bitwise XOR operation on the left and right hand operands.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Fdo:&lt;ObjDIR&gt;                                     |
\-------------------------------------------------------------------------/</pre>
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=== Fds - Directory to Locate Source File (SrcDIR) ===
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


This option affects the [[00022.htm|SrcDIR]]variable and allows the user to specify a source directory from which source file(s) will be loaded; by default this variable is empty and source file(s) are searched for in the current working directory. This value is ignored if the source file name included absolute or relative path information.
;Examples
Lower  EQU  0101y          ; 7h - binary radix suffix
Upper  EQU  1100y          ; Eh - binary radix suffix
MOV  AX, Upper XOR Lower  ; moves 1001 into AX


If the value specified in this option is anything other than an unadorned '''''drive letter''(for example, '''D:''') or a string ending with a '''''path separator character''('''/'''or '''\'''), then the '''''path separator character''appropriate for the underlying operating system is appended to the string.'''''''''
==== Bitwise AND Expression ====
;Description
A '''Bitwise AND Expression''' is one where an optional binary bitwise '''AND''' operation between the left and right operands is performed and the result returned.


<br />
;Syntax


<pre>/-------------------------------------------------------------------------\
''AND-Expression:''
|Type|Global|Group|File|Default                                          |
:''NOT-Expression''
|----+------+-----+----+--------------------------------------------------|
:''AND-Expression'' AND ''NOT-Expression''
|P  |Yes  |Yes  |Yes |-Fds:&lt;SrcDIR&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Fei - Control Include File Extension (IncEXT) ===
===== Bitwise AND (AND Operator) =====
;Syntax
''AND-Expression'' '''AND''' ''NOT-Expression''


This option determines whether or not the value of the [[00011.htm|IncEXT]]variable is appended to file names generated by the preprocessor when processing the INCLUDE directive. The parameterized version of this option affects the actual value of the [[00011.htm|IncEXT]]variable.
;Description
The '''AND''' operator performs a binary bitwise AND operation on the left and right hand operands.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
Lower  EQU  0111y          ; 7h - binary radix suffix
|----+------+-----+----+--------------------------------------------------|
  Upper  EQU  1110y          ; Eh - binary radix suffix
|S  |Yes  |Yes |Yes |-Fei                                              |
|    |      |    |    |(the value of IncEXT is not appended to include  |
MOV  AX, Upper XOR Lower   ; moves 0110 into AX
|   |      |    |    |file names)                                      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Fei:&lt;IncEXT&gt;                                     |
\-------------------------------------------------------------------------/</pre>
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=== Fel - Control Listing File Extension (LstEXT) ===
==== Bitwise One's Complement Expression ====
;Description
A '''Bitwise One's Complement Expression''' is one that performs an optional unary bitwise negation of its operand and returns the result.


This option determines whether or not the value of the [[00013.htm|LstEXT]]variable is appended to listing file names. The parameterized version of this option affects the actual value of the [[00013.htm|LstEXT]]variable.
;Syntax
''NOT-Expression:''
''Relational-Expression''
NOT ''Relational-Expression''


<br />
===== Bitwise One's Complement (NOT Operator) =====
;Syntax
'''NOT''' ''Relational-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''NOT''' operator performs a unary bitwise negation on its operand.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Fel                                              |
|    |      |    |    |(the value of LstEXT is appended to listing file  |
|    |      |    |    |names)                                            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |+Fel:&lt;LstEXT&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Fem - Control Messages File Extension (MsgEXT) ===
;Constraints
The operand must evaluate to a ''Constant-ExpressionType''.


This option determines whether or not the value of the [[00016.htm|MsgEXT]]variable is appended to messages file names. The parameterized version of this option affects the actual value of the [[00016.htm|MsgEXT]]variable.
;Examples
  Value  EQU 0111y          ; 7h - binary radix suffix


<br />
  MOV    EAX, NOT Value    ; moves FFFFFFF8 into EAX


<pre>/-------------------------------------------------------------------------\
====Relational Expression====
|Type|Global|Group|File|Default                                          |
;Description
|----+------+-----+----+--------------------------------------------------|
A '''Relational Expression''' is one where an optional binary comparision operation between the left and right operands is performed and the result returned.
|S  |Yes  |Yes  |Yes |+Fem                                              |
|    |      |    |    |(the value of MsgEXT is appended to messages file |
|    |      |    |    |names)                                            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |+Fem:&lt;MsgEXT&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Feo - Control Object File Extension (ObjEXT) ===
;Syntax
:''Relational-Expression:''
:''Additive-Expression''
:''Relational-Expression'' EQ ''Additive-Expression''
:''Relational-Expression'' NE ''Additive-Expression''
:''Relational-Expression'' GT ''Additive-Expression''
:''Relational-Expression'' GE ''Additive-Expression''
:''Relational-Expression'' LT ''Additive-Expression''
:''Relational-Expression'' LE ''Additive-Expression''


This option determines whether or not the value of the [[00019.htm|ObjEXT]]variable is appended to object file names. The parameterized version of this option affects the actual value of the [[00019.htm|ObjEXT]]variable.
=====Equal To (EQ Operator)=====
;Syntax
:''Relational-Expression'' '''EQ''' ''Additive-Expression''


<br />
;Description
The '''EQ''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are equal, and false (all bits off) if they are not equal.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
Each operand must evaluate to a ''Constant-ExpressionType''.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Feo                                              |
|    |      |    |    |(the value of ObjEXT is appended to object file  |
|    |      |    |    |names)                                            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |+Feo:&lt;ObjEXT&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Fes - Control Source File Extension (SrcEXT) ===
;Examples
  IF 1234 EQ 5678
    TRUE = 1
  ELSE
    TRUE = 0                ; Sets TRUE to 0
  ENDIF


This option determines whether or not the value of the [[00023.htm|SrcEXT]]variable is appended to source file names. The parameterized version of this option affects the actual value of the [[00023.htm|SrcEXT]]variable.
=====Not Equal To (NE Operator)=====
;Syntax
:''Relational-Expression'' '''NE''' ''Additive-Expression''


<br />
;Description
The '''NE''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are not equal, and false (all bits off) if they are equal.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
Each operand must evaluate to a ''Constant-ExpressionType''.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Fes                                              |
|    |      |    |    |(the value of SrcEXT is appended to source file  |
|    |      |    |    |names)                                            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |+Fes:&lt;SrcEXT&gt;                                    |
\-------------------------------------------------------------------------/</pre>
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=== Listing Control Options ===
;Examples
IF 1234 NE 5678
    TRUE = 1                ; Sets TRUE to 1
ELSE
    TRUE = 0
ENDIF


This section describes all options related to controlling the content of the assembler listing file. All listing control options begin with the letter '''&quot;L&quot;'''.
=====Greater Than (GT Operator)=====
;Syntax
:''Relational-Expression'' '''GT''' ''Additive-Expression''


Options that manipulate the characteristics of individual listing file columns reference a particular column by having a single character mnemonic identifier as part of the option identifier. Listing column mnemonics are as follows:
;Description
The '''GT''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than the right operand, and false (all bits off) if it is not.


'''C''''''Conditional assembly nesting level'''is a numeric value that appears during processing of a conditional assembly directive and is incremented for each level of nesting that occurs.
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


'''D''''''Macro definition line number'''tracks line numbers for each new MACRO definition introduced into the assembly.
;Examples
IF 1234 GT 5678
  TRUE = 1
ELSE
  TRUE = 0              ; Sets TRUE to 0
ENDIF


'''F''''''True or false conditional flag'''appears during processing of a conditional assembly directive and is either a plus (+) character to denote that the conditional expression was TRUE and tokens appearing within the block are being interpreted, or a minus (-) character to denote that the conditional expression was FALSE and tokens appearing within the block are being ignored.
=====Greater Than or Equal To (GE Operator)=====
;Syntax
:''Relational-Expression'' '''GE''' ''Additive-Expression''


'''G''''''Generated machine code data'''column shows the hexadecimal values for data generated by machine instructions or data allocation statements.
;Description
The '''GE''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than or equal to the right operand, and false (all bits off) if it is not.


'''I''''''Include file nesting level'''is a numeric value that appears during processing of INCLUDE files and is incremented for each level of nesting that occurs.
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


'''L''''''Macro expansion indentation level'''is a text field whose width reflects the current nesting level of expanded macros, and whose value contains a simulated &quot;arrow&quot; using the &quot;---&gt;&quot; characters.
;Examples
IF 1234 GE 1234
    TRUE = 1                ; Sets TRUE to 1
ELSE
    TRUE = 0
ENDIF


'''M''''''Macro expansion nesting level'''is a numeric value that appears during macro expansions and is incremented for each level of nesting that occurs.
=====Less Than (LT Operator)=====
;Syntax
:''Relational-Expression'' '''LT''' ''Additive-Expression''


'''O''''''Location counter offset value'''is a numeric value displayed in hexadecimal notation and indicates the current offset of the location counter within the current segment or structure.
;Description
The '''LT''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than the right operand, and false (all bits off) if it is not.


'''S''''''Source line data'''column contains the text data of the current line in the input source file.
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


'''X''''''Cumulative listing line number'''is incremented for every new line that appears in the listing file.
;Examples
  IF 1234 LT 5678
      TRUE = 1              ; Sets TRUE to 1
  ELSE
      TRUE = 0
  ENDIF


'''Y''''''Individual source file line number'''tracks line numbers for the top-level source file and for each separate INCLUDE file.
=====Less Than or Equal To (LE Operator)=====
;Syntax
:''Relational-Expression'' '''LE''' ''Additive-Expression''


'''Z''''''Macro expansion line number'''tracks the current line number for each MACRO expanded during the assembly. <br />
;Description
The '''LE''' operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than or equal to the right operand, and false (all bits off) if it is not.


[[[00063.htm|prev]]][[[00065.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


=== Lc* - Control Display of Individual Columns ===
;Examples
  IF 1234 LE 1234
    TRUE = 1                  ; Sets TRUE to 1
  ELSE
    TRUE = 0
  ENDIF


This family of options controls whether or not an individual column physically appears in the listing file. The display of each column may be controlled with a switch option by using the standard ON (+) or OFF (-) switch values (see [[00037.htm|Switch Option]]) or by using the parameterized option syntax (see [[00038.htm|Parameterized Option]]) with one of the following keyword values in the argument field:
====Additive Expression====
;Description
A '''Additive Expression''' is one where an optional binary additive arithmetic operation between the left and right operands is performed and the result returned.


'''B'''Abbreviation for BLANK. <br />'''BLANK'''The column will appear as a place-holder in the listing file, but the column data will not be displayed. <br />'''OFF'''The column will not be displayed. <br />'''ON'''The column will be displayed. <br />'''Z'''Abbreviation for ZBLANK. <br />'''ZBLANK'''The column data will only display if its value is nonzero (valid only for numeric fields). <br />
;Syntax
:''Additive-Expression:''
:''Multiplicative-Expression''
:''Additive-Expression'' + ''Multiplicative-Expression''
:''Additive-Expression'' - ''Multiplicative-Expression''


<br />
=====Addition (+ Operator)=====
;Syntax
:''Additive-Expression'' '''+''' ''Multiplicative-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''+''' operator performs a binary addition operation on the left and right hand operands, and returns the result.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcX (display Cumulative Listing Line Number)    |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcY (display Individual Source File Line Number) |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcZ:Z (display Macro Expansion Line Number if not|
|    |      |    |    |zero)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcD:Z (display Macro Definition Line Number if  |
|    |      |    |    |not zero)                                        |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcL (display Macro Expansion Indentation Level)  |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcM:Z (display Macro Expansion Nesting Level if  |
|    |      |    |    |not zero)                                        |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcI:Z (display Include File Nesting Level if not |
|    |      |    |    |zero)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcC (display Conditional Assembly Nesting Level) |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcF (display True or False Conditional Flag)    |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcO (display Location Counter Offset Value)      |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcG (display Generated Machine Code Data)        |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcS (display Source Line Data)                  |
\-------------------------------------------------------------------------/</pre>
[[[00064.htm|prev]]][[[00066.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lcm* - Specify Left Margin for Individual Columns ===
;Constraints
One of the operands must evaluate to a ''Constant-ExpressionType''. If one of the operands references an external identifier, then the other operand must be a ''Constant-ExpressionType'' without an external reference. Both operands must be of scalar type.


This family of options specifies the left margin value for each individual column, which determines the number of blank spaces that will appear to the left of the column data.
;Examples
  VALUE = 100 + 11          ; sets VALUE to 111


<br />
=====Subtraction (- Operator)=====
;Syntax
:''Additive-Expression'' '''-''' ''Multiplicative-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''-''' operator performs a binary subtraction operation on the left and right hand operands, and returns the result.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmX:0 (Cumulative Listing Line Number)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmY:1 (Individual Source File Line Number)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmZ:1 (Macro Expansion Line Number)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmD:1 (Macro Definition Line Number)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmL:0 (Macro Expansion Indentation Level)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmM:1 (Macro Expansion Nesting Level)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmI:1 (Include File Nesting Level)              |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmC:1 (Conditional Assembly Nesting Level)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmF:1 (True or False Conditional Flag)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmO:2 (Location Counter Offset Value)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmG:2 (Generated Machine Code Data)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmS:2 (Source Line Data)                        |
\-------------------------------------------------------------------------/</pre>
[[[00065.htm|prev]]][[[00067.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lct* - Specify Truncation of Individual Columns ===
;Constraints
The right operand must evaluate to a ''Constant-ExpressionType'' and reference no external identifiers. If both operands are relocatable, they must reside within the same segment, in which case the result is converted to a ''Absolute-ExpressionType''. Both operands must be of scalar type.


This family of options specifies whether or not the data contained within an individual column will be truncated if it exceeds the column width, or whether it will overflow onto additional lines until the entire column contents have been printed.
;Examples
  VALUE = 111 - 11          ; sets VALUE to 100


<br />
====Multiplicative Expression====
;Description
A '''Multiplicative Expression''' is one where an optional binary multiplicative arithmetic operation between the left and right operands is performed and the result returned.


<pre>/-------------------------------------------------------------------------\
;Syntax
|Type|Global|Group|File|Default                                          |
:''Multiplicative-Expression:''
|----+------+-----+----+--------------------------------------------------|
:''Narrowed-Expression''
|S  |Yes  |Yes  |Yes |+LcmX (truncate Cumulative Listing Line Number)  |
:''Multiplicative-Expression'' * ''Narrowed-Expression''
|----+------+-----+----+--------------------------------------------------|
:''Multiplicative-Expression'' / ''Narrowed-Expression''
|S  |Yes  |Yes  |Yes |+LcmY (truncate Individual Source File Line      |
:''Multiplicative-Expression'' MOD ''Narrowed-Expression''
|    |      |    |    |Number)                                          |
:''Multiplicative-Expression'' SHL ''Narrowed-Expression''
|----+------+-----+----+--------------------------------------------------|
:''Multiplicative-Expression'' SHR ''Narrowed-Expression''
|S  |Yes  |Yes  |Yes |+LcmZ (truncate Macro Expansion Line Number)      |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcmD (do not truncate Macro Definition Line      |
|    |      |    |    |Number)                                          |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcmL (do not truncate Macro Expansion Indentation|
|    |      |    |    |Level)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcmM (truncate Macro Expansion Nesting Level)    |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcmI (truncate Include File Nesting Level)      |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcmC (truncate Conditional Assembly Nesting      |
|    |      |    |    |Level)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcmF (truncate True or False Conditional Flag)  |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcmO (do not truncate Location Counter Offset    |
|    |      |    |    |Value)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-LcmG (do not truncate Generated Machine Code    |
|    |      |    |    |Data)                                            |
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+LcmS (truncate Source Line Data)                |
\-------------------------------------------------------------------------/</pre>
[[[00066.htm|prev]]][[[00068.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lcw* - Specify Width of Individual Columns ===
=====Multiplication (* Operator)=====
;Syntax
:''Multiplicative-Expression'' '''*''' ''Narrowed-Expression''


This family of options specifies the width of each individual listing column in single character positions. Note that the width of column '''L'''( Macro Expansion Indentation Level) will vary according to the macro expansion nesting level (which is also displayed as a numeric value in column '''M''') if the nesting level value exceeds the column width. This behavior may be avoided by setting the width of column '''L'''such that its width never exceeds the value of column '''M''', or by turning off the display of column '''L'''altogether.
;Description
The '''*''' operator performs a binary multiplication operation on the left and right hand operands, and returns the result.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
   VALUE = 9 * 3                 ; sets VALUE to 27
|----+------+-----+----+--------------------------------------------------|
|P  |Yes   |Yes  |Yes |-LcmX:4 (Cumulative Listing Line Number)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmY:4 (Individual Source File Line Number)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmZ:3 (Macro Expansion Line Number)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmD:3 (Macro Definition Line Number)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmL:0 (Macro Expansion Indentation Level)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmM:2 (Macro Expansion Nesting Level)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmI:2 (Include File Nesting Level)              |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmC:2 (Conditional Assembly Nesting Level)      |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmF:1 (True or False Conditional Flag)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmO:4 (Location Counter Offset Value)          |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmG:24 (Generated Machine Code Data)            |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-LcmS:90 (Source Line Data)                      |
\-------------------------------------------------------------------------/</pre>
[[[00067.htm|prev]]][[[00069.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lc - Control display of false Conditional blocks ===
=====Division (/ Operator)=====
;Syntax
:''Multiplicative-Expression'' '''/''' ''Narrowed-Expression''


This switch determines whether or not sections of source code appear in the listing file when they are rendered inactive by a false conditional expression. By default, the assembler does not show source code in the listing file if it is skipped during conditional processing; turn this switch on if listing of all source code is desired.
;Description
The '''/''' operator performs a binary division operation on the left and right hand operands, and returns the result.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
   VALUE = 27 / 9                ; sets VALUE to 3
|----+------+-----+----+--------------------------------------------------|
|S  |Yes   |Yes  |Yes |-Lc (do not list false conditional blocks)        |
\-------------------------------------------------------------------------/</pre>
[[[00068.htm|prev]]][[[00070.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Ld - Control Display of Listing Directives ===
=====Remainder (MOD Operator)=====
;Syntax
:''Multiplicative-Expression'' '''MOD''' ''Narrowed-Expression''


This switch controls whether or not assembler listing directives appear in the listing output. Listing directives are shown by default; turn this switch off to hide them.
;Description
The '''MOD''' operator performs a binary modulus division operation on the left and right hand operands, and returns the remainder as the result.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
   VALUE = 18 MOD 4              ; sets VALUE to 2
|----+------+-----+----+--------------------------------------------------|
|S   |Yes  |Yes  |Yes |+Lc (show all listing directives)                |
\-------------------------------------------------------------------------/</pre>
[[[00069.htm|prev]]][[[00071.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Le - Control Display of Error/Warning/Info Messages ===
=====Bitwise Left Shift (SHL Operator)=====
;Syntax
:''Multiplicative-Expression'' '''SHL''' ''Narrowed-Expression''


By default, any time the assembler prints an Error, Warning, or Info message during the assembly, the message also appears in the listing file following the source line to which it refers. Turn this switch off if such messages are not desired in the listing output.
;Description
The '''SHL''' operator shifts the bits in the left hand operand to the left by the number of bits specified in the right hand operand, and returns the result.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
   VALUE = 1111y SHL 4          ; sets VALUE to 11110000y
|----+------+-----+----+--------------------------------------------------|
|S   |Yes  |Yes  |Yes |+Le (show messages in listing file)              |
\-------------------------------------------------------------------------/</pre>
[[[00070.htm|prev]]][[[00072.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lf - Control Use of FormFeed Characters ===
=====Bitwise Right Shift (SHR Operator)=====
;Syntax
:''Multiplicative-Expression'' '''SHR''' ''Narrowed-Expression''


When the assembler is generating formatted listing output and it needs to advance to the next page, it inserts the ASCII FormFeed character (0x0C) into the listing output stream. If this causes problems, turning this switch off will instead cause the assembler to generate the appropriate number of newline character sequences to perform the page eject operation.
;Description
The '''SHR''' operator shifts the bits in the left hand operand to the right by the number of bits specified in the right hand operand, and returns the result.


<br />
;Constraints
Each operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
   VALUE = 11110000y SHR 4      ; sets VALUE to 00001111y
|----+------+-----+----+--------------------------------------------------|
|S   |Yes  |Yes  |Yes |+Lf (the FormFeed character is used)              |
\-------------------------------------------------------------------------/</pre>
[[[00071.htm|prev]]][[[00073.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Li - Control Display of INCLUDE Files ===
====Narrowed Expression====
;Description
A '''Narrowed Expression''' is one that performs an optional unary narrowing operation on its operand and returns the result.


When the assembler processes source code stored in an INCLUDE file, by default the contents of the file are expanded in the listing output; depending on the types of files that are included, this behavior can result in large volumes of listing output. Turn this switch off if the expansion is not desired.
;Syntax
''Narrowed-Expression:''
:''Cast-Expression'' HIGH ''Cast-Expression''
:HIGHWORD ''Cast-Expression''
:LOW ''Cast-Expression''
:LOWWORD ''Cast-Expression''


<br />
=====Upper 8 Bits of WORD Expression (HIGH Operator)=====
;Syntax
:'''HIGH''' ''Cast-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''HIGH''' operator returns the upper 8 bits of a 16-bit expression. Only bits 8-15 are returned, even if the magnitude of the operand exceeds 16 bits.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Li (INCLUDE files are expanded in listing output)|
\-------------------------------------------------------------------------/</pre>
[[[00072.htm|prev]]][[[00074.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Llp - Specify Length of Page ===
;Constraints
The operand must evaluate to a ''Constant-ExpressionType''.


To correctly format the listing file for subsequent hardcopy output, the assembler must know how many physical lines of output will fit vertically on the printed page. This setting is especially important if the use of FormFeed characters has been turned off with the '''Lf'''option. The default value for this option is 66 lines per page.
;Examples
  FIRST  = 1234h
  SECOND = HIGH FIRST        ; Sets SECOND to 12h


<br />
=====Upper 16 Bits of DWORD Expression (HIGHWORD Operator)=====
;Syntax
:'''HIGHWORD''' ''Cast-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''HIGHWORD''' operator returns the upper 16 bits of a 32-bit expression. Only bits 16-31 are returned, even if the magnitude of the operand exceeds 32 bits.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Llp:66 (the default page length is 66 lines)    |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00071.htm|Lf - Control Use of FormFeed Characters]] <br />�[[00085.htm|Lwp - Specify Width of Page]] <br />
;Constraints
The operand must evaluate to a ''Constant-ExpressionType''.


[[[00073.htm|prev]]][[[00075.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
This operator is not available in M510 mode.


=== Lm - Control Display of Macro Expansions ===
;Examples
  FIRST  = 12345678h
  SECOND = HIGHWORD FIRST    ; Sets SECOND to 1234h


This switch controls whether or not the text body of an expanded macro appears in the listing output. While turning this switch on can be very useful when debugging macros, it can also result in large volumes of listing output if many macros are utilized. By default, macro expansions do not appear in the listing output; turn this switch on if this behavior is desired.
=====Lower 8 Bits of WORD Expression (LOW Operator)=====
;Syntax
:'''LOW''' ''Cast-Expression''


<br />
;Description
The '''LOW''' operator returns the lower 8 bits of its operand.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
The operand must evaluate to a ''Constant-ExpressionType''.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Lm (macro expansions do not appear in listing    |
|    |      |    |    |output)                                          |
\-------------------------------------------------------------------------/</pre>
[[[00074.htm|prev]]][[[00076.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lmb - Specify Bottom Margin ===
;Examples
  FIRST  = 1234h
  SECOND = LOW FIRST        ; Sets SECOND to 34h


This option determines how many blank lines will appear at the bottom of the page in the listing output; by default this value is 4. The correct behavior of this option depends on the setting of the '''Llp'''and '''Lf'''options, and that they match the settings of the physical output device. If there are problems with these settings, then the actual bottom margin may not appear to correctly reflect the value of this option.
=====Lower 16 Bits of DWORD Expression (LOWWORD Operator)=====
;Syntax
:'''LOWWORD''' ''Cast-Expression''


<br />
;Description
The '''LOWWORD''' operator returns the lower 16 bits of its operand.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
The operand must evaluate to a ''Constant-ExpressionType''.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Lmb:4 (4 blank lines at bottom of page)          |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00071.htm|Lf - Control Use of FormFeed Characters]] <br />�[[00073.htm|Llp - Specify Length of Page]] <br />�[[00077.htm|Lmb - Specify Middle Margin after Title]] <br />�[[00079.htm|Lmt - Specify Top Margin before Title]] <br />
This operator is not available in [[#M510]] mode.


[[[00075.htm|prev]]][[[00077.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Examples
  FIRST  = 12345678h
  SECOND = LOWWORD FIRST    ; Sets SECOND to 5678h


=== Lml - Specify Left Margin ===
==== Type Conversion Expression ====
;Description
A '''Type Conversion Expression''' is one that performs an optional type conversion operation on its operand and returns the result.


This option specifies the number of blank characters that are printed to the left of every line of listing output. The default value for this option is 4.
;Syntax
''Cast-Expression:''
: ''Element-Selection-Expression''
: OFFSET ''Cast-Expression''
: SEG ''Cast-Expression''
: THIS ''Element-Selection-Expression''
: TYPE ''Element-Selection-Expression''
: ''Cast-Expression'' PTR ''Cast-Expression''
: ''Cast-Expression'' : ''Cast-Expression''


<br />
===== Address Offset (OFFSET Operator) =====
;Description
The '''OFFSET''' operator returns the offset portion of its operand. For relocatable values, this is the offset into the segment or group to which the expression is relative.


<pre>/-------------------------------------------------------------------------\
;Syntax
|Type|Global|Group|File|Default                                          |
'''OFFSET''' ''Cast-Expression''
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Lml:4 (left margin is 4 blank characters wide)  |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00078.htm|Lmr - Specify Right Margin]] <br />�[[00085.htm|Lwp - Specify Width of Page]] <br />�[[00065.htm|Lcm* - Specify Left Margin for Individual Columns]] <br />
;Constraints
The operand may evaluate to any one of the following ''[[#ExpressionType]]s:''
* ''Absolute-ExpressionType''
* ''Constant-ExpressionType''
* ''Immediate-ExpressionType''
* ''Direct-ExpressionType''
* ''Indirect-ExpressionType''


[[[00076.htm|prev]]][[[00078.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Examples
CodeLabel:
        MOV  AX, CodeLabel            ; illegal, no data at address
        MOV  AX, OFFSET  CodeLabel  ; we want the address itself


=== Lmb - Specify Middle Margin after Title ===
===== Address Segment (SEG Operator) =====
;Syntax
'''SEG''' ''Cast-Expression''


This option specifies the number of blank lines that separate the assembler heading, the title and subtitle (if there are any), from both the '''''column ruler''(if there is one) and the body of the generated listing text. The default value for this option is 2 blank lines.'''
;Description
The '''SEG''' operator returns the segment or group to which a relocatable expression is relative.


<br />
;Constraints
The operand must evaluate to one of the following ''ExpressionTypes:''
* ''Immediate-ExpressionType''
* ''Direct-ExpressionType''
* ''Indirect-ExpressionType''
* ''Indexed-ExpressionType''


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
DATA    SEGMENT
|----+------+-----+----+--------------------------------------------------|
Stuff  DB    ?
|P   |Yes   |Yes  |Yes |-Lmm:2 (2 blank lines after title and subtitle,   |
        MOV   AX, SEG Stuff    ; This construct is
|   |      |    |    |and before ruler line)                            |
        MOV   AX, DATA        ; equivalent to this
\-------------------------------------------------------------------------/</pre>
DATA   ENDS
'''Related Information:'''


�[[00073.htm|Llp - Specify Length of Page]] <br />�[[00075.htm|Lmb - Specify Bottom Margin]] <br />�[[00079.htm|Lmt - Specify Top Margin before Title]] <br />�[[00081.htm|Lr - Control Display of Column Ruler]] <br />
====== Address Alias (THIS Operator) ======
;Syntax
'''THIS''' ''Element-Selection-Expression''


[[[00077.htm|prev]]][[[00079.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Description
The '''THIS''' operator returns an operand whose:
* ''Relative Frame'' attribute is set to that of the current segment
* ''Displacement'' attribute is set to the current location counter
* ''Type Declaration'' attribute is set to that of the expression given by the ''Element-Selection-Expression'' operand.


=== Lmr - Specify Right Margin ===
;Constraints
The operand must evaluate to a ''Type-ExpressionType''.


This option specifies the number of blank characters that are reserved (but not actually printed) to the right of every line of listing output. The default value for this option is 4.
;Examples
DATA      SEGMENT
ALIAS  EQU  THIS BYTE        ; reference this address as a byte
Stuff  DB    ?
        MOV  AL, ALIAS        ; This construct is
        MOV  AL, Stuff        ; equivalent to this
DATA    ENDS


<br />
===== Datatype Extraction (TYPE Operator) =====
;Syntax
'''TYPE''' ''Element-Selection-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''TYPE''' operator returns the ''Type-ExpressionType'' attribute of its operand.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Lmr:4 (right margin is 4 blank characters wide)  |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00076.htm|Lml - Specify Left Margin]] <br />�[[00085.htm|Lwp - Specify Width of Page]] <br />�[[00065.htm|Lcm* - Specify Left Margin for Individual Columns]] <br />
;Constraints
None


[[[00078.htm|prev]]][[[00080.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Examples
CODE    SEGMENT
        ASSUME  CS:CODE, DS:CODE
Stuff  DB      ?                        ; TYPE Stuff is BYTE
        MOV    [BX],(TYPE Stuff) PTR 1  ; stores 1 as a BYTE at [BX]
CODE    ENDS


=== Lmt - Specify Top Margin before Title ===
===== Type Conversion (PTR Operator) =====
;Syntax
''Cast-Expression'' '''PTR''' ''Cast-Expression''


This option specifies the number of blank lines that appear at the top of the page before any other listing output is generated. The default value for this option is 2 blank lines.
;Description
The '''PTR'''operator converts the right operand to the type specified by the left operand.


<br />
;Constraints
The left operand must be a ''Type-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
CODE    SEGMENT
|----+------+-----+----+--------------------------------------------------|
          MOV  BYTE PTR [BX], 1    ; stores 1 as a BYTE at [BX]
|P  |Yes  |Yes |Yes |-Lmt:2 (2 blank lines at the top of the page)     |
  CODE     ENDS
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00073.htm|Llp - Specify Length of Page]] <br />�[[00075.htm|Lmb - Specify Bottom Margin]] <br />�[[00077.htm|Lmb - Specify Middle Margin after Title]] <br />
===== Segment Override (: Operator) =====
;Syntax
''Cast-Expression'' ''':''' ''Cast-Expression''


[[[00079.htm|prev]]][[[00081.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Description
The ''':''' (colon) operator forces the right operand to have the ''Relative Frame'' attribute of the left operand.


=== Lp - Generate Listing on Specific Pass ===
;Constraints
The left operand must evaluate to one of the following ''[[#ExpressionType]]s:''
* ''Register-ExpressionType'' where the ''Register Value'' attribute is that of a ''Segment-Register''
* ''Immediate-ExpressionType'' where the ''Relative Frame'' attribute is that of a ''GroupName'' or ''SegmentName''.


This option allows the user to control whether or not listing information is generated on a specific pass of the assembler. By default, the assembler only generates listing information on pass two. If the user is encountering &quot;phase errors&quot; or other unusual situations, it may be helpful to request a listing for the first pass as well.
;Examples
DATA      SEGMENT
Variable  DW    ?
DATA      ENDS
DGROUP    GROUP DATA, CODE
CODE      SEGMENT
  ASSUME  CS:CODE, DS:DGROUP
  MOV      AX, DGROUP:Variable        ; insure Variable is relative to DGROUP
  ASSUME  DS:NOTHING
  MOV      BX, CS:Variable            ; access Variable through CS register
CODE      ENDS


The arguments to this option are either a series of numeric digits (without intervening white space) or the '''ALL'''or '''NONE'''keywords. In the default assembler configuration, use of the '''-Lp:ALL'''form is equivalent to specifying '''-Lp:12''', because the assembler makes two passes through the source file by default. The '''NONE'''keyword prevents generation of any pass- related information in the listing file; however, symbol table information will still appear if selected.
==== Element Selection Expression ====
;Description
A '''Element Selection Expression''' is one that optionally selects a specific element of its operand and returns a reference to it.


When using numeric digits to specify the desired pass numbers, a listing will only be generated for the numbers given in the argument field; the default setting (or settings given by previous occurrences of the option) will be discarded.
;Syntax
''Element-Selection-Expression:''
:''Sign-Expression'']]
:''Element-Selection-Expression'' [''Sign-Expression'']
:''Element-Selection-Expression'' .''Sign-Expression''


<br />
===== Subscript ([] Operator) =====
;Syntax
''Element-Selection-Expression'' '''[''' ''Sign-Expression'' ''']'''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''[]''' binary operator performs a subscripting (or ''indexing'') operation between the operand to the left of the brackets and the operand enclosed within the brackets. This is a simple additive operation of '''BYTE''' granularity; the arithmetic performed is not influenced by the ''Operand Size'' of either operand.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Lp:2 (listing on pass 2 only)                   |
\-------------------------------------------------------------------------/</pre>
[[[00080.htm|prev]]][[[00082.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lr - Control Display of Column Ruler ===
The syntax for this operator describes a binary operation between the left hand expression and the bracketed expression. The bracketed expression is also subject to the same operations performed during the processing of a standalone ''Indirected-Expression'' as described in the section on ''Primary-Expressions''.


This switch to determines whether or not the '''''column ruler''appears at the top of each page in the listing output. This ruler is simply a line of information containing a string of alphabetic characters corresponding to each vertical column of listing information. The ruler reflects the current width, margins, and placement of the various listing columns at the time each page is printed, and helps the user to determine which column they are looking at. Turn this switch off if display of the column ruler is not desired.'''
;Constraints
Only one of the operands may specify a relocatable value.


<br />
;Examples
CODE    SEGMENT
        ASSUME  CS:CODE, DS:CODE
Value    DB    0                        ;  Value [0]
          DB    1                        ;  Value [1]
          DB    2                        ;  Value [2]
          DB    3                        ;  Value [3]
          DB    4                        ;  Value [4]


<pre>/-------------------------------------------------------------------------\
  MOV      AL, Value [3]        ;   load AL with the fourth byte at Value (3)
|Type|Global|Group|File|Default                                          |
  MOV      BX, offset Value     ;  get address of Value
|----+------+-----+----+--------------------------------------------------|
  MOV      AL, [BX] [1] [2]     ;  also gets the fourth byte ( 3 )
|S   |Yes  |Yes  |Yes |+Lr (show the column ruler in listing output)    |
\-------------------------------------------------------------------------/</pre>
CODE    ENDS
[[[00081.htm|prev]]][[[00083.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Ls - Control Display of Symbol Table ===
===== Structure/Union Field Selection (. Operator) =====
;Syntax
''Element-Selection-Expression'' '''.''' ''Sign-Expression''


This switch determines whether or not a summary of the symbol table contents is included at the end of the listing file. The default behavior is to omit the symbol table summary; turn this switch on to include it.
;Description
The '''.''' (period) operator selects a structure or union field entry. It adds the left and right hand operands together and returns the result. The left operand should be an ''Indirect-ExpressionType'', ''Indexed-ExpressionType'', or ''Type-ExpressionType'' whose ''Type Declaration'' attribute resolves to that of a ''Structure-TypeName'' or ''Union-TypeName''. The right operand should refer to a ''FieldName'' defined within the referenced type.


<br />
The ''Operand Size'' attribute of the result depends on the operands involved. If both operands have an operand size, a ''Structure-FieldName'' appearing as the right hand operand would override the operand size of the left operand and would dictate the operand size of the resulting expression.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
Only one of the operands may specify a relocatable value.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Ls (do not include symbol table in listing      |
|    |      |    |    |output)                                          |
\-------------------------------------------------------------------------/</pre>
[[[00082.htm|prev]]][[[00084.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lt1 - Specify Title ===
;Examples
Number  STRUC
  One    DB  1
  Two    DW  2
Number  ENDS


This option allows the user to specify the text of a default title to be printed at the top of each listing page; there is no default title. Title information must be enclosed in double quotes &quot;&quot; if it contains white space characters.
; The following line is only allowed in MASM 5.10 mode ( OPTION OLDSTRUCTS )
  MOV  AX,[BX] .Two        ;  BX points to a "Number", get the "Two" entry
; In other modes, "Two" is private to the "Number" structure type, so
; one of the following methods are required :
  MOV  AX,(Number PTR[BX]).Two  ; Explicit override
  MOV  AX,[BX] + Number.Two    ; Fully qualified reference
  ASSUME BX:Number              ; Associate BX with "Number"
  MOV  AX,[BX].Two              ; then original syntax is allowed


<br />
==== Unary Arithmetic Expression ====
;Description
A '''Unary Arithmetic Expression''' is one that optionally alters the sign of its operand and returns the result.


<pre>/-------------------------------------------------------------------------\
;Syntax
|Type|Global|Group|File|Default                                          |
''Sign-Expression:''
|----+------+-----+----+--------------------------------------------------|
:''Primary-Expression''
|P  |Yes  |Yes  |Yes |-Lt1:&lt;empty&gt; (no default title information)      |
:-''Primary-Expression''
\-------------------------------------------------------------------------/</pre>
:+''Primary-Expression''
[[[00083.htm|prev]]][[[00085.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lt2 - Specify Subtitle ===
===== Unary Minus (- Operator) =====
;Syntax
'''-''' ''Primary-Expression''


This option allows the user to specify the text of a default subtitle to be printed at the top of each listing page; there is no default subtitle. Subtitle information must be enclosed in double quotes &quot;&quot; if it contains white space characters.
;Description
The '''-''' operator makes its operand into a negative number and returns the result.


<br />
;Constraints
The operand must evaluate to a ''Constant-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
Value  EQU  1
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes |Yes |-Lt2:&lt;empty&gt; (no default subtitle information)    |
  MOV  AX, -Value    ; move -1 into AX
\-------------------------------------------------------------------------/</pre>
[[[00084.htm|prev]]][[[00086.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Lwp - Specify Width of Page ===
===== Unary Plus (+ Operator) =====
;Syntax
'''+''' ''Primary-Expression''


To correctly format the listing file for subsequent hardcopy output, the assembler must know how many physical characters of output will fit horizontally on the printed page. The default value for this option is 132 character positions.
;Description
The '''+''' operator returns its operand.


<br />
;Constraints
The operand must evaluate to a ''[[#Constant-ExpressionType|Constant-ExpressionType]]''.


<pre>/-------------------------------------------------------------------------\
;Examples
|Type|Global|Group|File|Default                                          |
Value EQU 1
|----+------+-----+----+--------------------------------------------------|
MOV  AX,+Value ; move 1 into AX
|P  |Yes  |Yes |Yes |-Lwp:132 (the default page width is 132 character |
|    |      |    |    |positions)                                        |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00065.htm|Lcm* - Specify Left Margin for Individual Columns]] <br />�[[00067.htm|Lcw* - Specify Width of Individual Columns]] <br />
==== Primary Expression ====
;Description
A '''Primary Expression''' is one that returns an expression operand.


[[[00085.htm|prev]]][[[00087.htm|next]]][[[00063.htm|parent]]][[[toc.htm|TOC]]]<br />
;Syntax
''Primary-Expression:''
:''Literal-Operand''
:''Record-Constant''
:''Identifier-Operand''
:''Register-Operand''
:''Integral-TypeName-Operand''
:''Value-Substitution-Operand''
:LENGTH ''Identifier-Operand''
:LENGTHOF ''Identifier-Operand''
:MASK ''Identifier-Operand''
:SIZE ''Element-Selection-Expression''
:SIZEOF ''Element-Selection-Expression''
:WIDTH ''Identifier-Operand''
:''Parenthesized-Expression''
:''Indirected-Expression''
:''Compound-Initializer''


=== Lwt - Specify Tab Expansion Width ===
===== Literal Operand =====
;Syntax
''Literal-Operand:''
:''Floating-Point-Literal''
:''Integer-Literal''
:''String-Literal''


This option specifies the width of a tab character in blank spaces. Tab characters appearing in the source file are always expanded into blank spaces when output to the listing file; the default behavior is to expand tab characters to every eighth character position.
;Description
The assembler accepts several types of literal values as operands within expressions. ''Literal-Operands'' are converted to ''[[#ExpressionType]]s'' according to the following table:
{|class="wikitable"
|Floating-Point-Literal
|Floating-Point-ExpressionType
|-
|Integer-Literal
|Absolute-ExpressionType
|-
|String-Literal
|Absolute-ExpressionType if the string length is less than or equal to the current Address Size; a String-ExpressionType otherwise.
|}


<br />
The context where the expression is used determines whether or not a particular type of literal is legal.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
Arithmetic operations cannot be performed on ''[[#Floating-Point-Literal]]s'', thus they cannot be the operand of a unary or binary operator.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Lwt:8 (tab characters are 8 character positions  |
|    |      |    |    |wide)                                            |
\-------------------------------------------------------------------------/</pre>
[[[00086.htm|prev]]][[[00088.htm|next]]][[[00045.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Message Control Options ===
===== Value Substitution Operand =====
;Syntax
''Value-Substitution-Operand:''
:''Anonymous-Label-Alias''
:''Location-Counter-Alias''
:''Indeterminate-Value-Alias''
:'''FLAT'''


This section describes all options related to the output and control of assembler messages. All Message Control Options begin with the letter '''&quot;M&quot;'''.
;Description
These operands are used to retrieve specialized values that are calculated internally by the assembler.


[[[00087.htm|prev]]][[[00089.htm|next]]][[[00087.htm|parent]]][[[toc.htm|TOC]]]<br />
The '''FLAT''' operator returns an expression whose ''[[#Relative Frame]]'' is set to that of the predefined FLAT pseudo-group.


=== M - Control Individual Messages or Groups ===
;Constraints
The '''FLAT''' operand is only active when a 32-bit processor has been selected.


This option controls the types of messages that are displayed by manipulating '''''message group identifier flags''or individual message numbers. Only messages with a severity of '''Warning'''or '''Info'''are controllable with this option. Messages with a severity of '''Error''', '''System''', '''Fatal''', '''Internal''', or '''Usage'''cannot be suppressed.'''
===== Record Constant Operand =====
;Syntax
''Record-Constant:''
:''Identifier-Operand'' '''<''' ''Field-List'' '''>'''
:''Identifier-Operand'' '''{''' ''Field-List'' '''}'''


<br />
''Field-List:''
:''Attribute-Expression''
:''Field-List'' ''',''' ''Attribute-Expression''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
A ''Record-Constant'' provides a method of calculating a single numeric result value from a list of ''Record-FieldName'' values, and combining them together according to the definition of the ''Record-TypeName'' given by the ''Identifier-Operand''. The result value is a ''Constant-ExpressionType'' suitable for use as an instruction operand, or for assigning to a record variable.
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-M:W+ (all warning messages are enabled)          |
\-------------------------------------------------------------------------/</pre>
All assembler messages are assigned a unique message number, and '''Warning'''or '''Info'''messages may belong to one or more message groups. The message group identifier flags are defined as follows:


'''ALL'''All warning and informational messages <br />'''BLK'''Messages regarding block structure violations <br />'''COD'''Messages regarding code generation <br />'''FIL'''File manipulation messages <br />'''I''' All informational messages <br />'''PP''' Preprocessor messages <br />'''SRC'''Source file lexical analyzer messages <br />'''STA'''Assembly statistics <br />'''W''' All warning messages <br />
The ''Record-TypeName'' given by the ''Identifier-operand'' determines how the ''Field-List'' will be evaluated. The ''Attribute-Expression'' entries are position-dependent, and are matched with the corresponding ''Record-FieldName'' entries from the ''Record-TypeName'' definition to determine their width and shift values. ''Attribute-Expression'' entries may be omitted, in which case the default values from the record definition are used in the calculation.


Any sequence of message groups or message numbers may be specified in the argument field of the '''M'''option; each argument must be followed by a plus (+ ) or minus (-) character to turn the value on or off, and no intervening white space characters may appear between arguments.
;Constraints
The ''Identifier-Operand'' must resolve to a ''Record-TypeName''.
;Examples
<pre>
DATE_T  record  Year  : 7 = 0,  ; 0 is 1980
                  Month : 4 = 1,  ; January
                  Day  : 5 = 1    ; 1st
CODE SEGMENT
  mov  AX,DATE_T  < >                      ; January 1st, 1980
  mov  AX,DATE_T  < 1996 - 1980, 12, 25 >  ; Christmas, 1996
  mov  AX,DATE_T  < 10h, 0Ch, 19h >        ; equivalent values in hex
  mov  AX,DATE_T  < 10000y, 1100y, 11001y > ; equivalent values in binary
  mov  AX,2199h                            ; equivalent value manually coded
  mov  AX,0010000110011001y                ; and in binary
;        YYYYYYYMMMMDDDDD
CODE  ENDS
</pre>


See [[02911.htm|Assembler Messages]]for more information on message number values and the messages groups to which they belong.
===== Register Operand =====
;Syntax
''Register-Operand:''
:''Processor-Register''


[[[00088.htm|prev]]][[[00090.htm|next]]][[[00087.htm|parent]]][[[toc.htm|TOC]]]<br />
;Description
Processor registers are valid expression operands. The context where the expression is used determines the allowable register operands.


=== Mb - Control Printing of the Assembler Banner ===
;Constraints
The currently selected processor dictates whether or not a register is visible to the expression evaluator.


This switch controls whether or not the assembler start-up banner is printed. This switch is on by default; turn it off to suppress display of the banner.
===== Identifier Operand =====
;Syntax
''Identifier-Operand:''
:''Identifier''


<br />
;Description
When an ''Identifier'' is used in an expression, it returns a value according to its ''Identifier-Type'', as shown in the following table:
{|class="wikitable"
!width=20%|Identifier-Type
!VALUE RETURNED
|-
|Numeric-EquateName
|The value originally assigned to the equate.
|-
|Structure-FieldName
|The offset in bytes from the beginning of the structure.
|-
|Union-FieldName
|The offset in bytes from the beginning of the union (always 0).
|-
|Record-FieldName
|The shift-count required to reach the field within the record.
|-
|Record-TypeName
|The mask-value that isolates defined record fields from undefined fields.
|-
|Structure-TypeName
|Zero if mode is M510, otherwise the size of the structure in bytes (the operand size of the structure type).
|-
|Union-TypeName
|The size of the union in bytes (the operand size of the union type).
|-
|Typedef-TypeName
|The operand size of the underlying data-type represented by the Typedef-TypeName.
|-
|GroupName
|A Relative Frame attribute that represents the group, and a Displacement value of zero.
|-
|SegmentName
|A Relative Frame attribute that represents the segment (or the group to which it belongs), and a Displacement value of zero if the mode is M510, or the current segment offset otherwise.
|-
|LabelName
|The Relative Frame attribute where the label is defined, and the segment offset value of the label.
|}


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
The ''Identifier'' must resolve to one of the following ''Identifier-Types:''
|----+------+-----+----+--------------------------------------------------|
* ''Numeric-EquateName''
|S  |Yes  |No  |No  |+Mb (Print the assembler banner)                  |
* ''FieldName''
\-------------------------------------------------------------------------/</pre>
* ''GroupName''
[[[00089.htm|prev]]][[[00091.htm|next]]][[[00087.htm|parent]]][[[toc.htm|TOC]]]<br />
* ''LabelName''
* ''SegmentName''
* ''UserDefined-TypeName''


=== Me - Set Number of Errors Before Assembler Aborts ===
===== Integral Type-Name Operand =====
;Syntax
''Integral-TypeName-Operand:''
:''Scalar-TypeName''
:''Distance-TypeName''


This option specifies the maximum number of errors that the assembler will tolerate before ending the assembly. The default value is 50.
;Description
When an ''Integral-TypeName-Operand''is used in an expression, it is converted to a ''Type-ExpressionType''. If used in a numeric context, the following numeric values are returned:
{|class="wikitable"
!Integral-TypeName-Operand||VALUE RETURNED
|-
|Scalar-TypeName||The operand-size of the type in bytes.
|-
|Distance-TypeName||If mode is M510, NEAR returns FFFF, and FAR returns FFFE.  Otherwise, NEAR and FAR are resolved and the values returned are:  NEAR16=FF02, NEAR32=FF04, FAR16=FF05, FAR32=FF06.
|}


<br />
;Constraints
The '''NEAR32''' and '''FAR32''' keywords are only valid if a 32-bit processor has been selected.


<pre>/-------------------------------------------------------------------------\
===== Number of Data Elements (LENGTH Operator) =====
|Type|Global|Group|File|Default                                          |
;Syntax
|----+------+-----+----+--------------------------------------------------|
'''LENGTH''' ''Identifier-Operand''
|P  |Yes  |Yes  |Yes |-Me:50 (abort the assembly after 50 errors are    |
|    |      |    |    |encountered)                                      |
\-------------------------------------------------------------------------/</pre>
[[[00090.htm|prev]]][[[00092.htm|next]]][[[00087.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Mwe - Treat Warnings as Errors ===
;Description
The '''LENGTH''' operator returns the number of data elements allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the length of the first element is considered.


This switch tells the assembler that any Warning messages are to be treated as though they were errors; this causes the assembler to end with a non- zero exit code, and helps prevent any warning conditions from &quot;passing by&quot; unnoticed.
;Constraints
The operand must evaluate to a ''Data-LabelName''.


<br />
===== Number of Data Elements (LENGTHOF Operator) =====
;Syntax
'''LENGTHOF''' ''Identifier-Operand''


<pre>/-------------------------------------------------------------------------\
;Description
|Type|Global|Group|File|Default                                          |
The '''LENGTHOF''' operator returns the number of data elements allocated to the operand.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Mwe (warnings are not considered to be errors)  |
\-------------------------------------------------------------------------/</pre>
[[[00091.htm|prev]]][[[00093.htm|next]]][[[00045.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Object Control Options ===
;Constraints
The operand must evaluate to a ''Data-LabelName''.


This section describes all options related to the output and control of object file information. All Object Control Options begin with the letter '''&quot;O&quot;'''.
This operator is not available in M510 mode.


[[[00092.htm|prev]]][[[00094.htm|next]]][[[00092.htm|parent]]][[[toc.htm|TOC]]]<br />
;Examples
<none>


=== Od - Line Number and Symbolic Debug Information in Object File ===
===== Record or Field Bit-Mask (MASK Operator) =====
;Syntax
'''MASK''' ''Identifier-Operand''


This switch controls whether or not all forms of debug information are included in the object file, and is a shorthand method of specifying the options to control '''''line numbering''and '''''symbolic''debug information.''''''
;Description
The '''MASK''' operator returns the bit mask required to isolate a field within a record.


The parameterized version of this option may be used to specify the format of the debugging information. The setting of this value may be necessary depending on which linker is used to link the object file output, or on the debugger used to debug the executable. The argument must be one of the following keywords:
;Constraints
The ''Identifier-Operand'' must resolve to a ''Record-TypeName'' or ''Record-FieldName''; otherwise the result is zero.


'''IBM32'''Generate debugging information in the 32-bit IBM (HLL) format. Executable code that is to be debugged with the IBM family of debuggers should use this setting. This is the default value if no parameter is specified. <br />'''MS16'''Generate debugging information in the 16-bit Microsoft (CodeView) format. You may need to use this setting if the object file output will be processed by a 16-bit linker, or if non-IBM debuggers will be utilized on the executable. <br />
===== Size of Variable in Bytes (SIZE Operator) =====
;Syntax
'''SIZE''' ''Element-Selection-Expression''


<br />
;Description
The '''SIZE''' operator returns the number of bytes allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the size of the first element is considered.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
None
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |(see default values for Ods and Odl)              |
|----+------+-----+----+--------------------------------------------------|
|P  |Yes  |Yes  |Yes |-Od:IBM32 (use the IBM debug format)              |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00094.htm|Odl - Line Numbering Information in Object File]] <br />�[[00095.htm|Ods - Symbolic Debug Information in Object File]] <br />
===== Size of Variable in Bytes (SIZEOF Operator) =====
;Syntax
'''SIZEOF''' ''Element-Selection-Expression''


[[[00093.htm|prev]]][[[00095.htm|next]]][[[00092.htm|parent]]][[[toc.htm|TOC]]]<br />
;Description
The '''SIZEOF''' operator returns the number of bytes allocated to the operand.


=== Odl - Line Numbering Information in Object File ===
;Constraints
This operator is not available in M510 mode.


This switch controls whether or not line numbering debug information is included in the object file, thus allowing the assembler source file to be viewed from within a source-level debugger.
===== Record or Field Width (WIDTH Operator) =====
;Syntax
'''WIDTH''' ''Identifier-Operand''


<br />
;Description
The '''WIDTH'''operator returns the width of a record or a record field name.


<pre>/-------------------------------------------------------------------------\
;Constraints
|Type|Global|Group|File|Default                                          |
The ''Identifier-Operand'' must resolve to a  ''Record-TypeName'' or ''Record-FieldName''; otherwise the result is zero.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Odl (line numbering debug information is not    |
|    |      |    |    |included in object file)                          |
\-------------------------------------------------------------------------/</pre>
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=== Ods - Symbolic Debug Information in Object File ===
===== Precedence (() Operator) =====
;Syntax
''Parenthesized-Expression:''
:'''(''' ''Attribute-Expression'' ''')'''


This switch controls whether or not symbolic debug information is included in the object file, thus allowing variables, labels, and expressions appearing in the assembler source file to be viewed from within a source- level debugger.
;Description
Parentheses forces the ''Attribute-Expression'' operand to be evaluated at a higher precedence level.


<br />
;Examples
Value =  2 + 3  * 4    ; Value = 14
Value = ( 2 + 3 ) * 4    ; Value = 20


<pre>/-------------------------------------------------------------------------\
===== Indirection ([] Operator) =====
|Type|Global|Group|File|Default                                          |
;Syntax
|----+------+-----+----+--------------------------------------------------|
''Indirected-Expression:''
|S  |Yes  |Yes  |Yes |-Ods (symbolic debug information is not included  |
:'''[''' ''Attribute-Expression'' ''']'''
|    |      |    |    |in object file)                                  |
\-------------------------------------------------------------------------/</pre>
[[[00095.htm|prev]]][[[00097.htm|next]]][[[00092.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Oug - Convert Global Identifiers to Uppercase ===
;Description
During evaluation of the ''Attribute-Expression'', the '''[]'''('''indirection''') operator will convert a ''Register-ExpressionType'' to a ''Indexed-ExpressionType'' by moving the ''Register Value'' attribute to either the ''Base Register'' or ''Index Register'' attribute field as appropriate for the register(s) referenced in the expression. This operation allows values contained in the processor registers to be used during effective address calculation at application run time.


This switch controls whether external identifiers (declared with the '''EXTERN''' directive) and public identifiers (declared with the '''PUBLIC'''directive) are converted to uppercase before writing them to the object file. By default, no conversion is performed and the symbols are written to the object file exactly as they were entered into the symbol table during assembly.
;Constraints
See the ''Indexed-ExpressionType'' section for information on registers that are valid for use in this context.


<br />
;Examples
CODE      SEGMENT
          ASSUME  CS : CODE ,  DS : CODE
Value    DW    0
          MOV    BX , offset  Value        ; load the address of Value into BX
          MOV    [ BX ] , BX                ; store the contents of BX into the
                                            ; memory location addressed by [BX]
CODE      ENDS


<pre>/-------------------------------------------------------------------------\
===== Compound Initializer List (<> Operator) =====
|Type|Global|Group|File|Default                                          |
;Syntax
|----+------+-----+----+--------------------------------------------------|
''Compound-Initializer:''
|S  |Yes  |Yes  |Yes |-Oug (do not convert global identifiers to        |
:'''<''' ''Initializer-List'' '''>'''
|    |      |    |    |uppercase in object file)                        |
:'''{''' ''Initializer-List'' '''}'''
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00101.htm|Scs - Control Case Sensitivity for Symbol Names]] <br />�[[00097.htm|Ous - Convert Group and Segment Names to Uppercase]] <br />
''Initializer-List:''
:''Duplicative-Expression''
:''Initializer-List'' ''',''' ''Duplicative-Expression''


[[[00096.htm|prev]]][[[00098.htm|next]]][[[00092.htm|parent]]][[[toc.htm|TOC]]]<br />
;Description
The '''<>''' (or '''{}''') operator provides a way of specifying a list of expressions to be used for initializing complex (multi-field) variables such as records or structures.


=== Ous - Convert Group and Segment Names to Uppercase ===
The '''<>''' operator encloses a list of comma-separated expressions; individual expressions are optional, but are also positional with respect to the record or structure fields they are intended to initialize. Commas must therefore be used to maintain field positions if empty expressions are encountered in the list.


This switch controls whether external group names (declared with the '''GROUP''' directive) and segment names (declared with the '''SEGMENT'''directive) are converted to uppercase before writing them to the object file. By default, no conversion is performed and the names are written to the object file exactly as they were entered into the symbol table during assembly.
The initializer list itself may also be left out entirely for those cases where a variable allocation will use the default initializers provided in the record or structure definition (the '''<>'''or '''{}''' themselves are still required).


<br />
;Examples
Numbers  STRUCT
  One    DB    0
  Two    DW    0
  Three  DB    0
  Four    DD    0
Numbers  ENDS
First    Numbers  < >               ;  empty initializer list
Second  Numbers  < 1, 2, 3, 4 >    ;  override all defaults
Third    Numbers  < 1 >            ;  override first entry only
Fourth  Numbers  < 1, , , 4 >      ;  override first and last entries


<pre>/-------------------------------------------------------------------------\
=== Expression Evaluation ===
|Type|Global|Group|File|Default                                          |
After an expression is parsed and checked for syntax errors, it is '''evaluated'''. During evaluation, all calculations and conversions are performed on the operands according to the operators that are applied to them. The final result is a collection of ''[[#Expression-Attribute]]s'', to which an ''ExpressionType'' is assigned.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Ous (do not convert group or segment names to   |
|    |      |    |    |uppercase in object file)                        |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00101.htm|Scs - Control Case Sensitivity for Symbol Names]] <br />�[[00096.htm|Oug - Convert Global Identifiers to Uppercase]] <br />
==== Expression Attributes ====
This section describes the ''Expression-Attributes''that are associated with an expression after it is evaluated.


[[[00097.htm|prev]]][[[00099.htm|next]]][[[00045.htm|parent]]][[[toc.htm|TOC]]]<br />
===== Address Size =====
If an expression refers to an effective address, then it also has an associated [[#address size]]. The following ''[[#ExpressionType]]s'' normally reference an effective address, and thus have an associated address size:
* ''Immediate-ExpressionType''
* ''Direct-ExpressionType''
* ''Indirect-ExpressionType''
* ''Indexed-ExpressionType''


=== Source Control Options ===
The address size can be either 2 ('''USE16''') or 4 ('''USE32'''). For an expression that references a label, the address size of the segment where the label is defined determines the address size of the expression.


All options related to parsing or processing the input source stream are described in this section. All Source Control Options begin with the letter '''&quot;S&quot;'''.
===== Operand Size =====
The ''Operand Size'' of an expression can be set explicitly using the [[#Type Conversion (PTR Operator)]], or it may be a side-effect inherited from the type of data referenced in the expression. The following table describes the operand sizes that will be assigned when an identifier is referenced in an expression:
{|class="wikitable"
!REFERENCE||OPERAND SIZE
|-
|8-Bit-Register||1
|-
|16-Bit-Register||2
|-
|32-Bit-Register||4
|-
|Segment-Register||2
|-
|Control-Register||4
|-
|Debug-Register||4
|-
|Test-Register||4
|-
|MMX-Register||8
|-
|Floating-Point-Register||10
|-
|BYTE||1
|-
|SBYTE||1
|-
|WORD||2
|-
|SWORD||2
|-
|DWORD||4
|-
|SDWORD||4
|-
|REAL4||4
|-
|FWORD||6
|-
|QWORD||8
|-
|REAL8||8
|-
|TBYTE||10
|-
|REAL10||10
|-
|NEAR||2 or 4
|-
|NEAR16||2
|-
|NEAR32||4
|-
|FAR||4 or 6
|-
|FAR16||4
|-
|FAR32||6
|-
|Numeric-EquateName||Inherited from equate expression
|-
|GroupName||2
|-
|SegmentName||2
|-
|Code-LabelName||SIZE (TYPE Code-LabelName)
|-
|Data-LabelName||SIZE (TYPE Data-LabelName)
|-
|Structure-FieldName||SIZE Structure-FieldName
|-
|Record-TypeName||SIZE Record-TypeName
|-
|Structure-TypeName||SIZE Structure-TypeName
|-
|Union-TypeName||SIZE Union-TypeName
|}
The ''Operand Size'' is 0 for all other identifier types.


[[[00098.htm|prev]]][[[00100.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />
===== Displacement =====
The ''Displacement'' value in an expression is the final calculated value of all numeric quantities, and must be a scalar value. It may also be a reference to a relocatable address, in which case the expression will also have a ''Relative Frame'' and/or an ''External Reference'' attribute. A ''Displacement'' may be used in the calculation of an effective address, either alone or in combination with a  ''Base Register'' and/or an ''Index Register''.


=== Sc - Control Case Sensitivity for All Identifiers ===
===== Relative Frame =====
The ''Relative Frame'' attribute will be present if the expression contains a direct or indirect reference to any of the following ''[[#Identifier-Type]]s:''
* ''GroupName''
* ''LabelName''
* ''SegmentName''


This switch controls whether or not all identifiers are case sensitive, and is a shorthand method of specifying the options for user identifiers and keywords.
The ''Relative Frame'' attribute indicates that the expression is relocatable, and specifies the ''GroupName'' or ''SegmentName'' to which the expression is relative.


<br />
===== External Reference =====
The ''External Reference'' attribute will be present if the expression references any external identifiers.


<pre>/-------------------------------------------------------------------------\
===== Register Value =====
|Type|Global|Group|File|Default                                          |
The ''Register Value'' attribute specifies the value of the ''Processor-Register'' referenced in a ''Register-ExpressionType''.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |(see default values for Sck and Scs)              |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00100.htm|Sck - Control Case Sensitivity for Keywords]] <br />�[[00101.htm|Scs - Control Case Sensitivity for Symbol Names]] <br />
===== Base Register =====
The ''Base Register'' attribute specifies the value for the base register used in an ''Indexed-ExpressionType''.


[[[00099.htm|prev]]][[[00101.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />
===== Index Register =====
The ''Index Register'' attribute specifies the value for the index register used in an ''Indexed-ExpressionType''.


=== Sck - Control Case Sensitivity for Keywords ===
===== Scale Factor =====
The ''Scale Factor'' attribute specifies the scaling value used (if any) in an ''Indexed-ExpressionType''.


This switch controls whether or not language keywords are case sensitive. By default, this flag is turned off; thus the spellings '''SEGMENT''', '''Segment''', and '''segment'''all refer to the same keyword. Turning this switch on would render the three spellings separate and distinct, and only the uppercase variant would be recognized as a keyword.
===== Type Declaration =====
The ''Type Declaration'' attribute specifies the type of data referenced in the expression. This is the value extracted from the expression when it is used as the left operand of the [[#Type Conversion (PTR Operator)]].


This option has no effect on user identifiers (see [[00101.htm|Scs - Control Case Sensitivity for Symbol Names]]) or processor mnemonics.
==== Expression Types ====
;Description
An ''ExpressionType'' is assigned to every expression during evaluation. The ''ExpressionType'' is used to determine whether or not an expression is legal for the context in which it is used. The type of an expression is influenced primarily by the operands that are used, but the use of expression operators also play an important part in determining the type of an expression.


<br />
;Definition
''ExpressionType:''
:''Absolute-ExpressionType''
:''Constant-ExpressionType''
:''Direct-ExpressionType''
:''Floating-Point-ExpressionType''
:''Immediate-ExpressionType''
:''Indirect-ExpressionType''
:''Indexed-ExpressionType''
:''Register-ExpressionType''
:''String-ExpressionType''
:''Type-ExpressionType''
:''Duplicated-ExpressionType''
:''Compound-ExpressionType''


<pre>/-------------------------------------------------------------------------\
===== Absolute Expression Type =====
|Type|Global|Group|File|Default                                          |
An ''Absolute-ExpressionType'' is an expression that evaluates to an integer quantity. Its value must be representable using one of the following types of scalar data:
|----+------+-----+----+--------------------------------------------------|
* '''BYTE'''
|S  |Yes  |Yes  |Yes |-Sck (All language keywords are case insensitive) |
* '''SBYTE'''
\-------------------------------------------------------------------------/</pre>
* '''WORD'''
[[[00100.htm|prev]]][[[00102.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />
* '''SWORD'''
* '''DWORD'''
* '''SDWORD'''
* '''FWORD'''
* '''QWORD'''
* '''TBYTE'''


=== Scs - Control Case Sensitivity for Symbol Names ===
The following restrictions apply to an ''Absolute-ExpressionType:''
* It cannot be relocatable (it may not contain references to a ''GroupName'', ''SegmentName'' or ''LabelName'').
* It cannot reference any external symbols.
* It cannot contain any forward references.


This switch controls whether or not user identifiers are case sensitive. By default, this flag is turned on; thus the identifiers '''GEORGE''', '''George''', and '''george'''are separate and distinct. Turning this switch off would cause the three spellings to refer to the same identifier.
===== Constant Expression Type =====
A ''Constant-ExpressionType'' is an ''Absolute-ExpressionType'' with the following restrictions relaxed:
* It may contain forward references to identifiers defined later in the source stream.
* It may reference a single external symbol, provided that the symbol was declared in an '''EXTERN''' directive with the '''ABS''' attribute.


If a case-insensitive assembly is being performed (-Scs), the actual spelling of the identifier is not altered (e.g., converted to uppercase) when it is entered into the symbol table. The actual symbol definition controls the spelling of the identifier regardless of whether or not a case -insensitive assembly was performed. The only exception to this rule is when processing a '''PUBLIC'''directive under MASM 5.10 emulation; the identifier spelling, which appears in the '''PUBLIC'''directive is honored over the one appearing in the actual identifier definition.
===== Immediate Expression Type =====
An ''Immediate-ExpressionType'' has all the properties of a ''Constant-ExpressionType'' with the following restrictions relaxed:
* It may contain references to a ''GroupName'', ''SegmentName'' or ''LabelName''(it may be relocatable).
* It may reference a relocatable external symbol.


This option has no effect on language keywords (see [[00100.htm|Sck - Control Case Sensitivity for Keywords]]), processor mnemonics, or register names.
An ''Immediate-ExpressionType'' must not be larger than 32 bits in magnitude; its value must be representable using one of the following types of scalar data:
*'''BYTE'''
*'''SBYTE'''
*'''WORD'''
*'''SWORD'''
*'''DWORD'''
*'''SDWORD'''


<br />
===== Direct Expression Type =====
A ''Direct-ExpressionType'' is an expression that references a ''Code-LabelName''. It can be used directly in code-relative instructions without conversion. There is no data type associated with the address that a ''Direct-ExpressionType'' represents, therefore It may not be used in a data-relative instruction without first being explicitly converted to another expression type.


<pre>/-------------------------------------------------------------------------\
===== Indirect Expression Type =====
|Type|Global|Group|File|Default                                          |
An ''Indirect-ExpressionType'' is an expression that references a ''Data-LabelName''. It can be used directly in data-relative instructions without conversion to another expression type.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |+Scs (All user identifiers are case sensitive)    |
\-------------------------------------------------------------------------/</pre>
'''Related Information:'''


�[[00096.htm|Oug - Convert Global Identifiers to Uppercase]] <br />�[[00097.htm|Ous - Convert Group and Segment Names to Uppercase]] <br />
===== Indexed Expression Type =====
An ''Indexed-ExpressionType'' is an expression that calculates an effective memory address using the contents of a '''Base-Register''', an '''Index-Register''', or both. A ''Processor-Register'' must first be converted to a ''Base-Register'' or ''Index-Register'' by specifying it as the operand of the [[#Indirection ([] Operator)]]before the expression can be converted to an ''Indexed-ExpressionType''.


[[[00101.htm|prev]]][[[00103.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />
When calculating a 16-bit effective address, only the '''BP''' and '''BX''' registers may be used as ''Base-Registers'', and only the '''DI''' and '''SI''' registers may be used as ''Index-Registers''.


=== Sk - Control Use of Reserved Words as Labels ===
When calculating a 32-bit effective address, only the '''EAX, EBX, ECX, EDX, EDI, ESI, EBP, and ESP''' registers may be used as ''Base-Registers'', and only the '''EAX, EBX, ECX, EDX, EDI, ESI, and EBP''' registers may be used as ''Index-Registers''.


This switch controls whether or not certain assembler keywords (reserved words) may be used in the context of a code label (for example, '''TEST:'''). By default, this switch is off, and keywords may not be used as labels.
'''Note:''' Only a single ''Base-Register'' and a single ''Index-Register'' may be used in a given expression.


Even when this switch is turned on, there are severe restrictions on this capability. Processor mnemonics classify as the only &quot;keywords&quot; allowed in this situation, and only in the context of a '''''code label''(a label followed by a colon); using any reserved word as a directive name or data label is illegal.'''
On 80386 (and higher) processors, the [[#Multiplication (* Operator)]] may be used with an ''Index-Register''operand and an ''Absolute-ExpressionType'' operand to establish a scaling factor that is applied to the ''Index-Register'' during effective address calculation. The scaling factor effectively causes the ''Index-Register'' to be multiplied by a fixed value at run time. The scaling ''Expression'' must evaluate to 1 (no scale factor), 2, 4, or 8.


<br />
A ''Direct-ExpressionType'' or an ''Indirect-ExpressionType'' may be a sub-expression of an ''Indexed-ExpressionType''.


<pre>/-------------------------------------------------------------------------\
===== Register Expression Type =====
|Type|Global|Group|File|Default                                          |
A ''Register-ExpressionType'' is an expression that specifies a single ''Processor-Register''.
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Sk (Reserved words may not be used as labels)    |
\-------------------------------------------------------------------------/</pre>
[[[00102.htm|prev]]][[[00104.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Sfs - SHORT is Default Distance for Forward-Referenced Jumps ===
===== String Expression Type =====
A ''String-ExpressionType'' is an expression that specifies a single ''String- Literal''.


By default, when the assembler encounters an unqualified forward reference as the operand to a jump instruction, it makes a worst-case assumption that the target will not be close enough to allow generating the '''SHORT'''variation of the instruction. Enough space is reserved to generate the '''NEAR'''version, and if it is determined later that the target is close enough, the '''SHORT''' variation is generated and extra space is padded with '''NOP'''instructions. This helps insure that source files will assemble without &quot;out of range&quot; errors, but wastes space when the '''NOP'''instructions are generated.
===== Floating-Point Expression Type =====
A ''Floating-Point-ExpressionType'' is an expression that specifies a single ''Floating-Point-Literal''.


Turning this switch on causes the assembler to assume that unqualified forward referenced jumps will always be reachable with the '''SHORT''' instruction variation; should this not be the case, an error is generated and the user may recode the instruction using the '''NEAR'''override.
===== Type Expression Type =====
A ''Type-ExpressionType''is an expression that specifies one of the following:
* A ''Scalar-TypeName''
* A ''Distance-TypeName''
* A ''UserDefined-TypeName''


<br />
===== Compound Expression Type =====
A ''Compound-ExpressionType'' evaluates to a list of (possibly nested) expressions collected together as a unit by the [[#Compound Initializer List ( <> Operator)]]. A ''Compound-ExpressionType''is used to initialize [[#aggregate]] data types (such as records, structures, and unions) and [[#vector]] data types (arrays).


<pre>/-------------------------------------------------------------------------\
===== Duplicated Expression Type =====
|Type|Global|Group|File|Default                                          |
A ''Duplicated-ExpressionType'' evaluates to an expression that is to be duplicated (repeated) a specified number of times. This type of expression is created using the [[#Duplicative Initialization (DUP Operator)]].
|----+------+-----+----+--------------------------------------------------|
|S  |Yes  |Yes  |Yes |-Sfs (default distance is NEAR)                   |
\-------------------------------------------------------------------------/</pre>
[[[00103.htm|prev]]][[[00105.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />


=== Sme - Control Visibility of MASM 6.00 Extended Mnemonics ===
==== Operand Expression Type ====
An ''Operand-ExpressionType'' consists of those ''[[#ExpressionType]]s'' that are valid for use as operands in processor instructions. The following ''ExpressionTypes'' are not valid for use as an ''Operand-ExpressionType:''
* ''Compound-ExpressionType''
* ''Duplicated-ExpressionType''
* A ''String-ExpressionType'' is only valid as an ''Operand-ExpressionType'' if it is short enough to be converted to an ''Absolute-ExpressionType'' having an ''Operand Size'' less than or equal to the current ''Address Size'' setting.


This option controls whether or not the following processor mnemonics are recognized as keywords: ''''''
''Operand-ExpressionType:''
:''Absolute-ExpressionType''
:''Constant-ExpressionType''
:''Immediate-ExpressionType''
:''Direct-ExpressionType''
:''Indirect-ExpressionType''
:''Indexed-ExpressionType''
:''Register-ExpressionType''
:''String-ExpressionType''
:''Floating-Point-ExpressionType''
:''Type-ExpressionType''


<br />FLDENVD <br />FLDENVW <br />FNSAVED <br />FNSAVEW <br />FNSTENVD <br />FNSTENVW <br />FRSTORD <br />FRSTORW <br />FSAVED <br />FSAVEW <br />FSTENVD <br />FSTENVW <br />IRETF <br />IRETDF <br />LOOPD <br />LOOPW <br />LOOPED <br />LOOPEW <br />LOOPNED <br />LOOPNEW <br />LOOPNZD <br />LOOPNZW <br />LOOPZD <br />LOOPZW <br />POPD <br />POPW <br />PUSHD <br />PUSHW <br />
;Description
An ''Operand-ExpressionType''consists of those ''[[#ExpressionType]]s'' that are valid for use as operands in processor instructions. The following ''ExpressionTypes'' are not valid for use as an ''Operand-ExpressionType:''
*''Compound-ExpressionType''
*''Duplicated-ExpressionType''


These mnemonics were introduced in MASM 6.00 to allow explicit word (16-bit ) or double-word (32-bit) operations on 80386 or newer processors. Although MASM 5.10 supports the 80386 processor, it does not recognize these keywords. To avoid conflicts with preexisting macro libraries, ALP will also refuse to recognize these keywords when operating under MASM 5.10 compatibility mode (-Sv:M510) unless this option is turned on. This option is turned on automatically when the -Sv:M600 option is used.
A ''String-ExpressionType'' is only valid as an ''Operand-ExpressionType'' if it is short enough to be converted to an ''Absolute-ExpressionType'' having an ''Operand Size'' less than or equal to the current ''Address Size'' setting.


<br />
;Definition


<pre>/-------------------------------------------------------------------------\
''Operand-ExpressionType:''
|Type|Global|Group|File|Default                                          |
:''Absolute-ExpressionType''
|----+------+-----+----+--------------------------------------------------|
:''Constant-ExpressionType''
|S  |Yes  |Yes  |Yes |-Sme (extended mnemonics are not enabled)        |
:''Immediate-ExpressionType''
\-------------------------------------------------------------------------/</pre>
:''Direct-ExpressionType''
'''Related Information:'''
:''Indirect-ExpressionType''
:''Indexed-ExpressionType''
:''Register-ExpressionType''
:''String-ExpressionType''
:''Floating-Point-ExpressionType''
:''Type-ExpressionType''


�[[00105.htm|Sv - Set Version Behavior]] <br />
==== Initializer Expression Type ====
An ''Initializer-ExpressionType'' consists of those ''[[#ExpressionType]]s'' that are valid for use in initializing variables. The following ''ExpressionTypes'' are not valid ''Initializer-ExpressionTypes:''
*''Indexed-ExpressionType''
*''Register-ExpressionType''


[[[00104.htm|prev]]][[[00106.htm|next]]][[[00098.htm|parent]]][[[toc.htm|TOC]]]<br />
''Initializer-ExpressionType:''
:''Scalar-Initializer-ExpressionType''
:''Compound-ExpressionType''
:''Duplicated-ExpressionType''


=== Sv - Set Version Behavior ===
''Scalar-Initializer-ExpressionType:''
:''Absolute-ExpressionType''
:''Constant-ExpressionType''
:''Immediate-ExpressionType''
:''Direct-ExpressionType''
:''Indirect-ExpressionType''
:''String-ExpressionType''
:''Floating-Point-ExpressionType''
:''Type-ExpressionType''


This option controls the various modes of compatibility that the assembler is designed to emulate. The argument to the '''Sv'''option must be one of the following keywords:
;Description
An ''Initializer-ExpressionType'' consists of those ''[[#ExpressionType]]s'' that are valid for use in initializing variables. The following ''ExpressionTypes'' are not valid ''Initializer-ExpressionTypes:''
*''Indexed-ExpressionType''
*''Register-ExpressionType''


'''ALP'''Native operating mode; don't emulate other assemblers <br />'''M510'''Emulate Microsoft MASM Version 5.10 <br />'''M600'''Emulate Microsoft MASM Version 6.00 <br />
;Definition
''Initializer-ExpressionType:''
:''Scalar-Initializer-ExpressionType''
:''Compound-ExpressionType''
:''Duplicated-ExpressionType''


<br />
''Scalar-Initializer-ExpressionType:''
:''Absolute-ExpressionType''
:''Constant-ExpressionType''
:''Immediate-ExpressionType''
:''Direct-ExpressionType''
:''Indirect-ExpressionType''
:''String-ExpressionType''
:''Floating-Point-ExpressionType''
:''Type-ExpressionType''


<pre>/-------------------------------------------------------------------------\
== Text Preprocessor ==
|Type|Global|Group|File|Default                                          |
The text preprocessor is a functional unit within the assembler that performs the '''''text preprocessing''''' translation phase. During text preprocessing, the following actions are performed:
|----+------+-----+----+--------------------------------------------------|
#Language Elements are recognized.
|P  |Yes  |Yes  |Yes |+Sv:ALP (do not emulate other assemblers)        |
#Text equates and macros are expanded.
\-------------------------------------------------------------------------/</pre>
#Macro directives and conditional assembly directives are recognized and processed.
'''Related Information:'''
#The preprocessed output is passed on to the assembler for final processing.


�[[00104.htm|Sme - Control Visibility of MASM 6.00 Extended Mnemonics]] <br />
This section also describes the various types of preprocessor directives:
{|class="wikitable"
!Type
!Function
!Directives
|-
|Conditional Assembly
|Tests for a specified condition and assembles a block of statements if the condition is true.
|IF IFB IFDEF IFDIFI IFE IFIDN IFNB IFNDEF IF1 IF2 ELSE ENDIF
|-
|Text Equate
|Allows assignment of simple text strings to a symbolic name. Provides functions for expanding and operating on the values.
|CATSTR EQU INSTR SIZESTR SUBSTR
|-
|Macro
|Provides text processing that is done sequentially at assembly time. By the end of assembly, ALP expands all macros and assembles the resulting text into object code.
|ENDM EXITM FOR FORC IRP IRPC LOCAL MACRO PURGE REPEAT REPT
|-
|Miscellaneous
|Miscellaneous text processing functions.
|COMMENT ECHO %OUT INCLUDE
|}


[[[00105.htm|prev]]][[[00107.htm|next]]][[[00025.htm|parent]]][[[toc.htm|TOC]]]<br />
=== Text Operators ===
;Description
The [[#Text Preprocessor]] recognizes certain punctuator characters as text operators. The programmer may use these operators to force the Text Preprocessor to perform various operations such as delineating text, expanding arguments, and converting expressions into their text representations.


=== The MASM2ALP Utility ===
;Syntax
''Text-Operator:''
:''Literal-Character-Operator''
:''Literal-Text-Operator''
:''Text-Expansion-Operator''
:''Text-Substitution-Operator''


MASM2ALP is a utility that accepts a MASM 5.10-compatible command line, transforms the command line parameters to the appropriate ALP syntax, and invokes '''alp.exe'''to perform the assembly. This allows the use of ALP instead of MASM in existing build environments without requiring major changes to makefiles or build scripts. You simply replace your existing MASM executable with MASM2ALP and resume operations.
==== Literal Character Operator (!) ====
;Syntax
''Literal-Character-Operator:''
:'''!''' any printable character


MASM2ALP accepts the following MASM 5.10-style command line syntax: <br />
;Description
When you use an exclamation point (!) in an operand, ALP treats the next character literally. (!) is typically used to prevent the assembler from recognizing and acting upon special characters such as the semicolon (;) or the ampersand (&), forcing them to appear as normal data characters.


<pre>masm2alp  [ Options ]  SourceFile  [ , [ ObjectFile ]  [ , [ ListingFile ]  [ , [ CrossRefFile ] ] ] ]  [ ; ] </pre>
;Constraints
'''Notes:'''
The ''Literal-Character-Operator'' has no effect when used inside of a ''String-Literal''.


�'''''Options''are normally specified first on the command line, but may appear anywhere before the optional semicolon (;) terminator. Options may begin with either a slash (/) or a dash (-), but once the first option is encountered, no further mixing of introductory characters is allowed. Options are not case sensitive. Individual command line options are discussed below.'''
;Examples
In this example, use of the ! in the second macro argument prevents the assembler from interpreting the rest of the line as a comment:
MACRONAME  First, !; NonComment, Third              ; Comment


�Filename arguments are position-dependent. Commas (,) must be used to separate each argument and to maintain argument position, both when arguments are explicitly specified or when they are skipped (left unspecified). The filename argument descriptions are as follows:
=== Literal Text Operator (<>) ===
;Syntax
''Literal-Text-Operator:''
:'''<''' ''Char-Sequence'' '''>'''


'''''SourceFile''This argument is mandatory, and specifies the name of the assembly language source file to be processed. If no filename suffix is supplied, a default value of &quot;.asm&quot; is assumed.'''
''Char-Sequence''
:any printable character
:''Char-Sequence'' any printable character


'''''ObjectFile''The optional name of the object-code output file to be produced. If no filename suffix is supplied, a default value of &quot;.obj&quot; is assumed. If no '''''ObjectFile''argument is given, the root portion of the '''''SourceFile'' argument is used as the name of the object file.'''''''''
;Description
The literal-text operator directs the assembler to treat ''Char-Sequence'' as a single literal element regardless of whether it contains commas, spaces, or other separators. The operator is most often used with macro calls and the FOR directive to ensure that values in a parameter list are treated as a single parameter.


'''''ListingFile''The optional name of the listing output file to be produced. If no filename suffix is supplied, a default value of &quot;.lst&quot; is assumed. If no '''''ListingFile''argument or '''-L'''option is given, then no listing file is produced; otherwise the root portion of the '''''SourceFile''argument is used as the name of the listing file.'''''''''
The literal-text operator can also be used to force ALP to treat other special characters such as the semicolon (;) or the ampersand (&) literally. For example, the semicolon inside angle brackets (<>) becomes a semicolon, not a comment indicator.


'''''CrossRefFile''The optional name of the cross-reference output file. Since ALP does not support the creation of a cross-reference file, MASM2ALP ignores this argument.'''
ALP removes one set of angle brackets each time the parameter is used in a macro. When using nested macros, you will need to supply as many sets of angle brackets as there are levels of nesting. The assembler recognizes nested occurrences of text literals.


�The trailing semicolon (;) operator may be used when no more filename arguments are to be specified and the default values are to be utilized for the remaining arguments. Any arguments or command line options that follow the semicolon will be ignored.
;Examples
The following example illustrates how to pass arbitrary text to a macro as a single parameter:
MACRONAME  First, <Second Argument>, <Third, <Nested>, Argument>


�MASM2ALP does not support the &quot;prompting&quot; behavior of Microsoft MASM when insufficient command line arguments are supplied. A syntax error is issued in this event. <br />
The macro will receive three separate arguments:
# First
# Second Argument
# Third, <Nested>, Argument


'''Options:'''
Notice that the outermost set of angle brackets were removed from the second and third arguments.


MASM2ALP accepts the following command line options:
==== Text Expansion Operator (%) ====
;Syntax
''Text-Expansion-Operator:''
:'''%''' 2nd through Nth token on line
:'''%''' ''Text-EquateName''
:'''%''' ''Expression''


'''-A'''Forces MASM to write segments to the object file in alphabetical order. MASM normally writes segments in source code order. MASM2ALP ignores this option.
;Description
The '''%''' ''Text-Expansion-Operator'' has different effects depending upon the context in which it is used. Its primary purpose is convert various sources of information into text literals that may in turn be passed to macros as arguments.


'''-B'''''number''Sets the size of the source file read buffer in 1K increments. MASM2ALP ignores this option.
The '''%''' ''Text-Expansion-Operator'' causes the following types of conversions:


'''-C'''Tells MASM to create a cross-reference file. MASM2ALP ignores this option.
;Line Expansion
When used as the first token on the line, the '''%''' operator forces expansion of ''Text-EquateNames'' in contexts where they would otherwise be left unexpanded. ''Text-EquateNames'' passed as arguments to macros are not automatically expanded; this is one context where the '''%''' operator is useful.


'''-d'''Causes the assembler to generate listing file information during both pass 1 and 2. By default, the assembler only generates listing file information during pass 2.
;Expansion of a Text Equate Operand
As with '''''Line Expansion''''', the '''%''' operator may be used within the body of a line to expand individual ''Text-EquateNames''. This can be useful when expansion of all ''Text-EquateNames'' on the line is not desired.


'''-D'''''symbol[=value]''Defines a symbol visible during assembly. An optional text value may also be specified for the symbol.
;Conversion of Numeric Expression to Text
If the ''Text-Expansion-Operator''is not the first token on the line or immediately followed by a ''Text-EquateName'', then the argument of the '''%''' operator is assumed to be an ''Expression'', which is evaluated and converted to the text representation of its value. This is useful when the need arises to pass the text representation of a number to a macro.


'''-E'''Tells MASM to generate code compatible with floating-point emulation libraries. MASM2ALP ignores this option.
;Constraints
When the '''%''' ''Expression'' form of the expansion operator is used, the ''Expression'' must evaluate to an ''Immediate-ExpressionType''.


'''-H'''Prints the help information panel for the command line syntax.
;Examples
MakErr      MACRO      X
LB          =          0
              REPEAT      X
LB          =          LB + 1
              MakLib      % LB
              ENDM        ; ; End of REPEAT
              ENDM        ; ; End of MACRO
MakLib      MACRO      Y
Err & Y :    DB    ' Error    & Y ' ,0
              ENDM
              MakErr  3
Err1 :    DB    ' Error  1 ' ,0
Err2 :    DB    ' Error  2 ' ,0
Err3 :    DB    ' Error  3 ' ,0


'''-I'''''path''Specifies an INCLUDE file search path.
==== Text Substitution Operator (&) ====
;Syntax
''Text-Substitution-Operator:''
:''Macro-ParameterName'' '''&'''
:'''&''' ''Macro-ParameterName''


'''-L[A]'''Forces the creation of a listing output file. The '''-LA'''option is an abbreviation for &quot;list all&quot;, which forces macro expansions and false conditionals to also be included in the listing output.
;Description
An ampersand (&) is used in the body of a macro to force the substitution of a ''Macro-ParameterName'' with the value of its argument during expansion of the macro.


'''- ML'''Directs the assembler to perform a case-sensitive assembly, and to preserve the case of external identifiers when writing them to the object file.
;Constraints
The assembler does not substitute a ''Macro-ParameterName'' that is in a quoted string or not preceded by a delimiter in the expansion unless it is immediately preceded by an ampersand (&).


'''-MU'''Directs the assembler to perform a case-insensitive assembly, and to convert the names of external identifiers to uppercase when writing them to the object file. This is the default mode of operation for Microsoft MASM.
It is necessary to separate a ''Macro-ParameterName'' from other ''Identifer-Characters'' with an ampersand (&) before any substitution or paste operations are performed.


'''-MX'''Directs the assembler to perform a case-insensitive assembly, yet preserve the case of external identifiers when writing them to the object file.
;Examples
ErrGen    MACRO    X
Error &X: push      bx
ABX      mov      BX, "A";
AB &X    mp        ERROR
          ENDM


'''-N'''Prevents the symbol table summary from being printed in the listing file .
The statement '''ErrGen A''' produces this code:
ErrorA :  push    bx
ABX        mov      BX , "A";
ABA        jmp      ERROR


'''-P'''Causes MASM to check for inpure code operations when assembling for a privileged mode processor. This feature is not supported by ALP, thus MASM2ALP ignores this option.
=== Preprocessor Tokens ===
;Syntax
''Preprocessing-Token:''
:''Identifier''
:''Text-Literal''
:''FileName''
:''Comment''


'''-S'''Forces MASM to write segments to the object file in source code order, nullifying the effects of any previously encountered '''-A'''option. MASM2ALP ignores this option.
;Description
During the text preprocessing translation phase, certain conditions will cause the preprocessor to convert raw [[#Language Elements]] (''[[#Token]]s'') into ''Preprocessing-Tokens''. The act of text preprocessing typically causes ''Preprocessing-Tokens'' to either be removed from the input stream or converted back into ''Tokens'' before being passed on to the assembler for final processing.


'''-X'''Forces false conditionals to be included in the listing file output.
==== Text Literals ====
;Syntax
''Text-Literal:''
:operand of ''Literal-Character-Operator''
:operand of ''Literal-Text-Operator''


'''-Z'''Causes MASM to print the source line of any statement causing an assembly error to the standard output device. MASM2ALP ignores this option .
;Description
A ''Text-Literal'' is a single unit of text that is used by the [[#Text Preprocessor]] in many different text handling contexts. In some contexts ( such as the processing of arguments to be passed to a macro), normal language ''[[#Token]]s'' are implicitly treated as ''Text-Literals'', provided they are not a delimiter character such as a comma or a blank. In other contexts, it may be necessary to explicitly convert a unit of text to a ''Text-Literal'' using the ''Literal-Text-Operator''.


'''-ZD'''Causes line number debugging information to be included in the object file output.
;Constraints
A normal language ''Token'' is never implicitly considered to be a ''Text-Literal'' if a ''Text-Literal'' is explicitly required in the syntax of the construct being parsed.


'''-ZI'''Causes both line number and symbolic debugging information to be included in the object file output. <br />
=== File Names ===
;Syntax
''FileName:''
:''FileName-Text''
:''Text-Literal''


[[[00106.htm|prev]]][[[00108.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
''FileName-Text:''
:''FileName-Character''
:''FileName-Text FileName-Character''


=== Language Elements ===
''FileName-Character:''
:any printable character except blank (ASCII 32)


;Description
''FileName'' arguments may be coded as an arbitrary sequence of printable characters, or as a ''Text-Literal''; use the ''Text-Literal'' form if the ''FileName'' is to contain embedded spaces or other special characters.


-----
If path information is included in the ''FileName'', you can separate the individual directory names with either the back slash (\) or the forward slash (/) and they will be treated identically by the assembler.


The following sections describe the elements you use to build an ALP program source file.
;Examples
  INCLUDE      <inc\macros.inc>
  INCLUDELIB  os2386.lib


'''Character Set'''
=== Comments ===
'''''Comments''''' are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.


All elements in an assembler language source file are built from collections of characters contained in the '''character set''', which are defined as:
There are two classes of comments recognized by ALP:


�The uppercase and lowercase letters of the English alphabet <br />�The decimal digits 0 through 9 <br />�The following graphic characters: <br />
* Comments that start with a character sequence and continue to the end of the line (''EndOfLine-Comment'')


<pre>~  !  &quot;  #  $  %  ^  &amp;  '   (  )   |
* Comments that start with a character sequence and continue until the occurrence of another character sequence (''Block-Comment''). See the [[#COMMENT]] directive for a description of ''[[#Block-Comment]]s''.
*  +  ,  -  .   /  :  ;  =  &lt;  &gt;  ?
[   \  ]   _  {  }  @ </pre>
<br />�The space and horizontal tab characters <br />�The end of line character(s)


'''White Space'''
There are two types of ''EndOfLine-Comments:''


White space is a character or contiguous stream of characters that is ignored or removed from the input stream by the ALP preprocessor.
'''''Macro-Comment'''''


'''White space characters'''are any contiguous sequence of one or more space or tab characters not enclosed in single or double quotes. White space characters are significant only in that they serve to separate language tokens from one another; they are removed from the input stream by the scanner. <br />
'''''Macro-Comments''''' (beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of ''Macro-Comments'' can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, ''Macro-Comments'' are discarded and not entered into the macro definition, whereas ''NonMacro-Comments'' are treated as normal text and are retained.


'''''NonMacro-Comment'''''


-----
'''''NonMacro-Comment''''' (beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions.


''Token'''':'' <br />[[00110.htm|''Reserved-Word'']] <br />[[00149.htm|''Identifier'']] <br />[[00199.htm|''Literal'']] <br />[[00246.htm|''Punctuator'']] <br /> <br />
;Syntax


[[[00107.htm|prev]]][[[00109.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
''Comment:''
:''EndOfLine-Comment''
:''Block-Comment''


=== Description ===
''EndOfLine-Comment:''
:''NonMacro-Comment''
:''Macro-Comment''


The following sections describe the elements you use to build an ALP program source file.
''NonMacro-Comment:''
:''';''' ''Char-Sequence''


'''Character Set'''
''Macro-Comment:''
:''';;''' ''Char-Sequence''


All elements in an assembler language source file are built from collections of characters contained in the '''character set''', which are defined as:
''Char-Sequence:''
:any printable character
:''Char-Sequence'' any printable character


�The uppercase and lowercase letters of the English alphabet <br />�The decimal digits 0 through 9 <br />�The following graphic characters: <br />
''[[#Block-Comment]]:''
:See the [[#COMMENT]] directive


<pre>~  !  &quot;   #  $  %  ^  &amp;  '  (  )  |
;Description
*  +  ,  -  .  /  :  ;  =  &lt;  &gt;  ?
[  \  ]  _  {  }  @ </pre>
<br />�The space and horizontal tab characters <br />�The end of line character(s)


'''White Space'''
'''''Comments''''' are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.


White space is a character or contiguous stream of characters that is ignored or removed from the input stream by the ALP preprocessor.
There are two classes of comments recognized by ALP:
* Comments that start with a character sequence and continue to the end of the line (''EndOfLine-Comment'')
* Comments that start with a character sequence and continue until the occurrence of another character sequence (''Block-Comment''). See the [[#COMMENT]] directive for a description of ''[[#Block-Comment]]s''.


'''White space characters'''are any contiguous sequence of one or more space or tab characters not enclosed in single or double quotes. White space characters are significant only in that they serve to separate language tokens from one another; they are removed from the input stream by the scanner. <br />
There are two types of ''EndOfLine-Comments:''


[[[00108.htm|prev]]][[[00110.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
'''''Macro-Comment'''''


=== Syntax ===
'''''Macro-Comments''''' (beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of ''Macro-Comments'' can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, ''Macro-Comments'' are discarded and not entered into the macro definition, whereas ''NonMacro-Comments'' are treated as normal text and are retained.


''Token'''':'' <br />[[00110.htm|''Reserved-Word'']] <br />[[00149.htm|''Identifier'']] <br />[[00199.htm|''Literal'']] <br />[[00246.htm|''Punctuator'']] <br /> <br />
'''''NonMacro-Comment'''''


[[[00109.htm|prev]]][[[00111.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
'''''NonMacro-Comment''''' (beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions.


=== Reserved Words ===
;Example


The following are examples of ''EndOfLine-Comments:''


-----
; Comments may be on a line all by themselves. They can be empty ...
;
                        ; They don't have to start in the first column
BumpCount MACRO Amount  ; They can appear to the right of statements
  Count = Count + Amount      ; This appears in macro expansions
  $Total = $Total + Amount    ;; This does not, discarded during definition
ENDM


This section describes all of the assembler reserved words.
=== Text Arguments ===
Many preprocessing directives operate on sequences of raw text characters called ''Text-Arguments''. A ''Text-Argument''may be specified using any one of several methods:
* Specifying the text directly using a raw ''Text-Literal''.
* Using the ''Text-Expansion-Operator'' to convert a numeric expression to its text representation.
* Using a ''Text-EquateName'' in those contexts where a ''Text-Argument''is expected. In this case the preprocessor will automatically resolve the ''Text-EquateName'' and use its value as the ''Text-Argument''.


''Text-Argument:''
:''Text-Literal''
:'''%''' ''Expression''
:''Text-EquateName''


-----
;Description
Many preprocessing directives operate on sequences of raw text characters called ''Text-Arguments''. A ''Text-Argument''may be specified using any one of several methods:


''Reserved-Word'''':'' <br />[[00113.htm|''Preprocessor-Directive'']] <br />[[00116.htm|''Assembler-Directive'']] <br />[[00119.htm|''Processor-Mnemonic'']] <br />[[00122.htm|''Processor-Register'']] <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br />[[00131.htm|''Language-Name'']] <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />[[00143.htm|''Directive-Keyword'']] <br />[[00146.htm|''Operator-Keyword'']] <br /> <br />
* Specifying the text directly using a raw ''Text-Literal''.
* Using the ''Text-Expansion-Operator'' to convert a numeric expression to its text representation.
* Using a ''Text-EquateName'' in those contexts where a ''Text-Argument'' is expected. In this case the preprocessor will automatically resolve the ''Text-EquateName'' and use its value as the ''Text-Argument''.


[[[00110.htm|prev]]][[[00112.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
;Syntax
''Text-Argument:''
:''Text-Literal''
:'''%''' ''Expression''
:''Text-EquateName''


=== Description ===
=== Conditional Assembly Directives ===
At assembly time, ALP evaluates conditional assembly directives, assembling if the conditions are true. You can use conditional assembly directives when you want to test for a specified condition and assemble a block of statements if the condition is true. The [[#IFxx]] and [[#ENDIF]] directives enclose the statements to be considered for conditional assembly. The optional [[#ELSEIFxx]] and [[#ELSE]] blocks follow the [[#IFxx]] directive. There are many forms of the [[#IFxx]] and [[#ELSEIFxx]] directives.


This section describes all of the assembler reserved words.
This section describes the following conditional assembly directives:
:[[#IF]]
:[[#IFB]]
:[[#IFDEF]]
:[[#IFDIF]]
:[[#IFDIFI]]
:[[#IFE]]
:[[#IFIDN]]
:[[#IFIDNI]]
:[[#IFNB]]
:[[#IFNDEF]]
:[[#IF1]]
:[[#IF2]]
:[[#ELSE]]
:[[#ENDIF]]


[[[00111.htm|prev]]][[[00113.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
=== IFxx (Begin Primary Conditional Block) ===
You can use each '''IFxx'''conditional directive with the [[#ELSExx]], [[#ELSE]] and [[#ENDIF]] directives to provide the statements to be considered for conditional assembly. ALP assembles the statements following the [[#IFxx]] directive only if this condition is true.


=== Syntax ===
'''Syntax'''
IFxx  operand
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF


''Reserved-Word'''':'' <br />[[00113.htm|''Preprocessor-Directive'']] <br />[[00116.htm|''Assembler-Directive'']] <br />[[00119.htm|''Processor-Mnemonic'']] <br />[[00122.htm|''Processor-Register'']] <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br />[[00131.htm|''Language-Name'']] <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />[[00143.htm|''Directive-Keyword'']] <br />[[00146.htm|''Operator-Keyword'']] <br /> <br />
'''Remarks'''


[[[00112.htm|prev]]][[[00114.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
The following directives are members of the '''IFxx''' family:
* IF
* IFB
* IFDEF
* IFDIF
* IFDIFI
* IFE
* IFIDN
* IFIDNI
* IFNB
* IFNDEF
* IF1
* IF2


=== Preprocessor Directives ===
You can nest the conditional directives to any level. They are not limited to use within a macro. The assembler must know any operand to a conditional on pass one to avoid errors and incorrect evaluation.


=== IF (If Expression is True) ===
'''IF''' starts a conditional assembly statement, which is ended by the corresponding [[#ENDIF]] conditional assembly directive. Each '''IF''' directive must be ended by a matching ENDIF directive.


-----
'''Syntax'''
<pre>
IF Expression
    .
    .
    .
[ ELSEIFxx ]  (optional)
    .
    .
    .
[ ELSE ]  (optional)
    .
    .
    .
ENDIF
</pre>


'''''Preprocessor Directives''are symbolic names that describe the various assembly-time text processing instructions interpreted by the preprocessor phase of the assembler.'''
'''Remarks'''


If the [[#IFxx]] conditional assembly statement is not ended by an [[#ENDIF]] directive, an ''unterminated conditional''  message is produced by the assembler. An ENDIF without a matching '''IF''' causes an error. ENDIF does not have an operand.


-----
'''Note:''' The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.


''Preprocessor-Directive'''':'' one of <br />'''<br />'''
'''Example'''
IF  debug
      EXTERN  dump:FAR
      EXTERN  trace:FAR
      EXTERN  breakpoint:FAR
ENDIF


<pre>CATSTR      COMMENT    ELSE        ELSEIF
=== IFB (If Argument is Blank) ===
ELSEIF1    ELSEIF2    ELSEIFB    ELSEIFDEF
This is true if ''[[#Text-Argument]]'' is blank (contains no characters).
ELSEIFDIF  ELSEIFDIFI  ELSEIFE    ELSEIFIDN
ELSEIFIDNI  ELSEIFNB    ELSEIFNDEF  ENDIF
ENDM        EQU        EXITM      FOR
FORC        IF          IF1        IF2
IFB         IFDEF      IFDIF      IFDIFI
IFE        IFIDN      IFIDNI      IFNB
IFNDEF      INCLUDE    INSTR      IRP
IRPC        LOCAL      MACRO      PURGE
REPEAT      REPT        SIZESTR    SUBSTR</pre>
<br /> <br />


[[[00113.htm|prev]]][[[00115.htm|next]]][[[00113.htm|parent]]][[[toc.htm|TOC]]]<br />
;Syntax
IFB Text-Argument


=== Description ===
;Remarks
A ''[[#Text-Argument]]'' must be specified, the contents of which are checked for the presence of characters. An error is generated if a ''Text-Argument'' is not supplied.


''Preprocessor Directives''are symbolic names that describe the various assembly-time text processing instructions interpreted by the preprocessor phase of the assembler.
=== IFDEF (If Identifier is Defined) ===
This is true if ''[[#Identifier]]'' has been defined as a label, variable, or symbol.


[[[00114.htm|prev]]][[[00116.htm|next]]][[[00113.htm|parent]]][[[toc.htm|TOC]]]<br />
;Syntax
IFDEF Identifier


=== Syntax ===
=== IFDIF (If Arguments Are Different) ===
This is true if ''[[#Text-Argument]]-1'' and ''Text-Argument-2'' are different in a case-sensitive comparison.


''Preprocessor-Directive'''':'' one of <br />'''<br />'''
;Syntax
IFDIF Text-Argument-1, Text-Argument-2


<pre>CATSTR      COMMENT    ELSE        ELSEIF
;Remarks
ELSEIF1    ELSEIF2    ELSEIFB    ELSEIFDEF
Both ''Text-Argument'' arguments must be specified. An error is generated if a either argument is not supplied.
ELSEIFDIF  ELSEIFDIFI  ELSEIFE    ELSEIFIDN
ELSEIFIDNI  ELSEIFNB    ELSEIFNDEF  ENDIF
ENDM        EQU        EXITM      FOR
FORC        IF          IF1        IF2
IFB        IFDEF      IFDIF      IFDIFI
IFE        IFIDN      IFIDNI      IFNB
IFNDEF      INCLUDE    INSTR      IRP
IRPC        LOCAL      MACRO      PURGE
REPEAT      REPT        SIZESTR    SUBSTR</pre>
<br /> <br />


[[[00115.htm|prev]]][[[00117.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
;Example
In the following example:
IFDIF <EAGLES>,<Eagles>;
  value = 1
ENDIF
the condition would be true; the arguments are different because they are compared with a case-sensitive algorithm.


=== Assembler Directives ===
=== IFDIFI (If Arguments Are Spelled Differently) ===
This is true if ''[[#Text-Argument]]-1'' and ''Text-Argument-2'' are different in a case-insensitive comparison.


;Syntax
IFDIFI Text-Argument-1, Text-Argument-2


-----
;Remarks
Both ''Text-Argument'' arguments must be specified. An error is generated if a either argument is not supplied.


'''''Assembler Directives''are symbolic names that describe the various assembly- time instructions interpreted by the assembler itself.'''
;Example
In the following example:
IFDIFI <EAGLES>, <Eagles>
  value = 1
ENDIF


the condition would be false; the arguments are not different because they are compared using a case-insensitive algorithm.


-----
=== IFE (If Expression is Not True) ===
This is true if ''expression'' is 0.


''Assembler-Directive'''':'' one of <br />'''<br />'''
'''Syntax'''


<pre>.186          .286          .286C        .286P
  IFE  Expression
.287          .386          .386C        .386P
.387          .486          .486C        .486P
.586          .586P        .686          .686P
.8086        .8087          ALIGN        .ALPHA
  ASSUME      %BIN          .CODE          COMM
.CONST        .CREF        .DATA        .DATA?
DB            DD            DF            DOSSEG
.DOSSEG        DQ            DT            DW
ECHO          END          ENDP          ENDS
EQU          .ERR          .ERR1        .ERR2
.ERRB        .ERRDEF      .ERRDIF      .ERRDIFI
.ERRE        .ERRIDN      .ERRIDNI      .ERRNB
.ERRNDEF      .ERRNZ        EVEN          EXTERN
EXTERNDEF    EXTRN        .FARDATA      .FARDATA?
GROUP        INCLUDELIB    LABEL        .LALL
.LFCOND      .LIST        .LISTALL      .LISTIF
.LISTMACRO    .LISTMACROALL  LOCAL        .MMX
.MODEL        NAME        .NOCREF      .NOLIST
.NOLISTIF    .NOLISTMACRO  .NOMMX        OPTION
ORG          %OUT          PAGE          PROC
PUBLIC      .RADIX        RECORD      .SALL
SEGMENT      .SEQ          .SFCOND      .STACK
STRUC        STRUCT        SUBTITLE      SUBTTL
.TFCOND        TITLE        TYPEDEF      UNION
.XALL        .XCREF        .XLIST</pre>
<br /> <br />


[[[00116.htm|prev]]][[[00118.htm|next]]][[[00116.htm|parent]]][[[toc.htm|TOC]]]<br />
=== IFIDN (If Arguments Are Identical) ===
This is true if ''[[#Text-Argument]]-1'' and ''Text-Argument-2'' are identical in a case -sensitive comparison.


=== Description ===
'''Syntax'''
IFIDN  Text-Argument - 1, Text-Argument - 2


''Assembler Directives''are symbolic names that describe the various assembly- time instructions interpreted by the assembler itself.
'''Remarks'''


[[[00117.htm|prev]]][[[00119.htm|next]]][[[00116.htm|parent]]][[[toc.htm|TOC]]]<br />
Both ''Text-Argument'' arguments must be specified. An error is generated if a either argument is not supplied.


=== Syntax ===
'''Example'''


''Assembler-Directive'''':'' one of <br />'''<br />'''
In the following example:


<pre>.186          .286          .286C        .286P
IFIDN  <EAGLES>, <Eagles>;
.287          .386          .386C        .386P
   value  =  1
.387          .486          .486C        .486P
  ENDIF
.586          .586P        .686          .686P
the condition would be false; the arguments are not identical because they are compared using a case-insensitive algorithm.
.8086        .8087          ALIGN        .ALPHA
ASSUME      %BIN          .CODE          COMM
.CONST        .CREF        .DATA        .DATA?
DB            DD            DF            DOSSEG
.DOSSEG        DQ            DT            DW
ECHO          END          ENDP          ENDS
EQU          .ERR          .ERR1        .ERR2
.ERRB        .ERRDEF      .ERRDIF      .ERRDIFI
.ERRE        .ERRIDN      .ERRIDNI      .ERRNB
.ERRNDEF      .ERRNZ        EVEN          EXTERN
EXTERNDEF    EXTRN        .FARDATA      .FARDATA?
GROUP        INCLUDELIB   LABEL        .LALL
.LFCOND      .LIST        .LISTALL      .LISTIF
.LISTMACRO    .LISTMACROALL LOCAL        .MMX
.MODEL        NAME        .NOCREF      .NOLIST
.NOLISTIF    .NOLISTMACRO  .NOMMX        OPTION
ORG          %OUT          PAGE          PROC
PUBLIC      .RADIX        RECORD      .SALL
SEGMENT      .SEQ          .SFCOND      .STACK
STRUC        STRUCT        SUBTITLE      SUBTTL
.TFCOND        TITLE        TYPEDEF      UNION
.XALL        .XCREF        .XLIST</pre>
<br /> <br />


[[[00118.htm|prev]]][[[00120.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
=== IFIDNI (If Arguments Are Spelled Identically) ===
This is true if ''[[#Text-Argument]]-1'' and ''Text-Argument-2'' are identical in a case -insensitive comparison.


=== Processor Mnemonics ===
'''Syntax'''
IFIDNI  Text-Argument - 1, Text-Argument - 2


'''Remarks'''


-----
Both ''Text-Argument'' arguments must be specified. An error is generated if a either argument is not supplied.


'''''Processor Mnemonics''are symbolic names given to the various instructions in the processor instruction set.'''
'''Example'''


In the following example:
IFIDNI <EAGLES>, <Eagles>
  value = 1
ENDIF
the condition would be true; the arguments are identical because they are compared using a case-insensitive algorithm.


-----
=== IFNB (If Argument is Not Blank) ===
This is true if ''Text-Argument'' is not blank (characters are present).


''Processor-Mnemonic'''':'' one of <br />'''<br />'''
'''Syntax'''
IFNB Text-Argument
'''Remarks'''


<pre>AAA        AAD        AAM        AAS        ADC
A ''Text-Argument'' must be specified, the contents of which are checked for the presence of characters. An error is generated if a ''Text-Argument'' is not supplied.
ADD        AND        ARPL      BOUND      BSF
BSR        BSWAP      BT        BTC        BTR
BTS        CALL      CBW        CDQ        CLC
CLD        CLI        CLTS      CMC        CMOVA
CMOVAE    CMOVB      CMOVBE    CMOVC      CMOVE
CMOVG      CMOVGE    CMOVL      CMOVLE    CMOVNA
CMOVNAE    CMOVNB    CMOVNBE    CMOVNC    CMOVNE
CMOVNG    CMOVNGE    CMOVNL    CMOVNLE    CMOVNO
CMOVNP    CMOVNS    CMOVNZ    CMOVO      CMOVP
CMOVPE    CMOVPO    CMOVS      CMOVZ      CMP
CMPS      CMPSB      CMPSD      CMPSW      CMPXCHG
CMPXCHG8B  CPUID      CWD        CWDE      DAA
DAS        DEC        DIV        EMMS      ENTER
ESC        F2XM1      FABS      FADD      FADDP
FBLD      FBSTP      FCHS      FCLEX      FCMOVB
FCMOVBE    FCMOVE    FCMOVNB    FCMOVNBE  FCMOVNE
FCMOVNU    FCMOVU    FCOM      FCOMI      FCOMIP
FCOMP      FCOMPP    FCOS      FDECSTP    FDISI
FDIV      FDIVP      FDIVR      FDIVRP    FENI
FFREE      FIADD      FICOM      FICOMP    FIDIV
FIDIVR    FILD      FIMUL      FINCSTP    FINIT
FIST      FISTP      FISUB      FISUBR    FLD
FLD1      FLDCW      FLDENV    FLDENVD    FLDENVW
FLDL2E    FLDL2T    FLDLG2    FLDLN2    FLDPI
FLDZ      FMUL      FMULP      FNCLEX    FNDISI
FNENI      FNINIT    FNOP      FNSAVE    FNSAVED
FNSAVEW    FNSTCW    FNSTENV    FNSTENVD  FNSTENVW
FNSTSW    FPATAN    FPREM      FPREM1    FPTAN
FRNDINT    FRSTOR    FRSTORD    FRSTORW    FSAVE
FSAVED    FSAVEW    FSCALE    FSETPM    FSIN
FSINCOS    FSQRT      FST        FSTCW      FSTENV
FSTENVD    FSTENVW    FSTP      FSTSW      FSUB
FSUBP      FSUBR      FSUBRP    FTST      FUCOM
FUCOMI    FUCOMIP    FUCOMP    FUCOMPP    FWAIT
FXAM      FXCH      FXTRACT    FYL2X      FYL2XP1
HLT        IDIV      IMUL      IN        INC
INS        INSB      INSD      INSW      INT
INTO      INVD      INVLPG    IRET      IRETD
IRETDF    IRETF      JA        JAE        JB
JBE        JC        JCXZ      JE        JECXZ
JG        JGE        JL        JLE        JMP
JNA        JNAE      JNB        JNBE      JNC
JNE        JNG        JNGE      JNL        JNLE
JNO        JNP        JNS        JNZ        JO
JP        JPE        JPO        JS        JZ
LAHF      LAR          LDS          LEA          LEAVE
LES          LFS          LGDT        LGS          LIDT
LLDT        LMSW        LOCK        LODS        LODSB
LODSD        LODSW        LOOP        LOOPD        LOOPE
LOOPED      LOOPEW      LOOPNE      LOOPNED      LOOPNEW
LOOPNZ      LOOPNZD      LOOPNZW      LOOPW        LOOPZ
LOOPZD      LOOPZW      LSL          LSS          LTR
MOV          MOVD        MOVQ        MOVS        MOVSB
MOVSD        MOVSW        MOVSX        MOVZX        MUL
NEG          NOP          NOT          OR          OUT
OUTS        OUTSB        OUTSD        OUTSW        PACKSSDW
PACKSSWB    PACKUSWB    PADDB        PADDD        PADDSB
PADDSW      PADDUSB      PADDUSW      PADDW        PAND
PANDN        PCMPEQB      PCMPEQD      PCMPEQW      PCMPGTB
PCMPGTD      PCMPGTW      PMADDWD      PMULHW      PMULLW
POP          POPA        POPAD        POPD        POPF
POPFD        POPW        POR          PSLLD        PSLLQ
PSLLW        PSRAD        PSRAW        PSRLD        PSRLQ
PSRLW        PSUBB        PSUBD        PSUBSB      PSUBSW
PSUBUSB      PSUBUSW      PSUBW        PUNPCKHBW    PUNPCKHDQ
PUNPCKHWD    PUNPCKLBW    PUNPCKLDQ    PUNPCKLWD    PUSH
PUSHA        PUSHAD      PUSHD        PUSHF        PUSHFD
PUSHW        PXOR        RCL          RCR          RDMSR
RDPMC        RDTSC        REP          REPE        REPNE
REPNZ        REPZ        RET          RETF        RETN
ROL          ROR          RSM          SAHF        SAL
SAR          SBB          SCAS        SCASB        SCASD
SCASW        SETA        SETAE        SETB        SETBE
SETC        SETE        SETG        SETGE        SETL
SETLE        SETNA        SETNAE      SETNB        SETNBE
SETNC        SETNE        SETNG        SETNGE      SETNL
SETNLE      SETNO        SETNP        SETNS        SETNZ
SETO        SETP        SETPE        SETPO        SETS
SETZ        SGDT        SHL          SHLD        SHR
SHRD        SIDT        SLDT        SMSW        STC
STD          STI          STOS        STOSB        STOSD
STOSW        STR          SUB          TEST        UC2
VERR        VERW        WAIT        WBINVD      WRMSR
XADD        XCHG        XLAT        XLATB        XOR </pre>
<br /> <br />


[[[00119.htm|prev]]][[[00121.htm|next]]][[[00119.htm|parent]]][[[toc.htm|TOC]]]<br />
=== IFNDEF (If Identifier is Not Defined) ===
This is true if ''symbol'' has not yet been defined as a label, variable, or symbol.


=== Description ===
'''Syntax'''
IFNDEF symbol


''Processor Mnemonics''are symbolic names given to the various instructions in the processor instruction set.
=== IF1 (If Assembling On Pass 1) ===
This is true on pass one.


[[[00120.htm|prev]]][[[00122.htm|next]]][[[00119.htm|parent]]][[[toc.htm|TOC]]]<br />
'''Syntax'''
IF1


=== Syntax ===
'''Remarks'''


''Processor-Mnemonic'''':'' one of <br />'''<br />'''
'''IF1''' does not have an operand.


<pre>AAA        AAD        AAM        AAS        ADC
=== IF2 (If Assembling On Pass 2) ===
ADD        AND        ARPL      BOUND      BSF
BSR        BSWAP      BT        BTC        BTR
BTS        CALL      CBW        CDQ        CLC
CLD        CLI        CLTS      CMC        CMOVA
CMOVAE    CMOVB      CMOVBE    CMOVC      CMOVE
CMOVG      CMOVGE    CMOVL      CMOVLE    CMOVNA
CMOVNAE    CMOVNB    CMOVNBE    CMOVNC    CMOVNE
CMOVNG    CMOVNGE    CMOVNL    CMOVNLE    CMOVNO
CMOVNP    CMOVNS    CMOVNZ    CMOVO      CMOVP
CMOVPE    CMOVPO    CMOVS      CMOVZ      CMP
CMPS      CMPSB      CMPSD      CMPSW      CMPXCHG
CMPXCHG8B  CPUID      CWD        CWDE      DAA
DAS        DEC        DIV        EMMS      ENTER
ESC        F2XM1      FABS      FADD      FADDP
FBLD      FBSTP      FCHS      FCLEX      FCMOVB
FCMOVBE    FCMOVE    FCMOVNB    FCMOVNBE  FCMOVNE
FCMOVNU    FCMOVU    FCOM      FCOMI      FCOMIP
FCOMP      FCOMPP    FCOS      FDECSTP    FDISI
FDIV      FDIVP      FDIVR      FDIVRP    FENI
FFREE      FIADD      FICOM      FICOMP    FIDIV
FIDIVR    FILD      FIMUL      FINCSTP    FINIT
FIST      FISTP      FISUB      FISUBR    FLD
FLD1      FLDCW      FLDENV    FLDENVD    FLDENVW
FLDL2E    FLDL2T    FLDLG2    FLDLN2    FLDPI
FLDZ      FMUL      FMULP      FNCLEX    FNDISI
FNENI      FNINIT    FNOP      FNSAVE    FNSAVED
FNSAVEW    FNSTCW    FNSTENV    FNSTENVD  FNSTENVW
FNSTSW    FPATAN    FPREM      FPREM1    FPTAN
FRNDINT    FRSTOR    FRSTORD    FRSTORW    FSAVE
FSAVED    FSAVEW    FSCALE    FSETPM    FSIN
FSINCOS    FSQRT      FST        FSTCW      FSTENV
FSTENVD    FSTENVW    FSTP      FSTSW      FSUB
FSUBP      FSUBR      FSUBRP    FTST      FUCOM
FUCOMI    FUCOMIP    FUCOMP    FUCOMPP    FWAIT
FXAM      FXCH      FXTRACT    FYL2X      FYL2XP1
HLT        IDIV      IMUL      IN        INC
INS        INSB      INSD      INSW      INT
INTO      INVD      INVLPG    IRET      IRETD
IRETDF    IRETF      JA        JAE        JB
JBE        JC        JCXZ      JE        JECXZ
JG        JGE        JL        JLE        JMP
JNA        JNAE      JNB        JNBE      JNC
JNE        JNG        JNGE      JNL        JNLE
JNO        JNP        JNS        JNZ        JO
JP        JPE        JPO        JS        JZ
LAHF      LAR          LDS          LEA          LEAVE
LES          LFS          LGDT        LGS          LIDT
LLDT        LMSW        LOCK        LODS        LODSB
LODSD        LODSW        LOOP        LOOPD        LOOPE
LOOPED      LOOPEW      LOOPNE      LOOPNED      LOOPNEW
LOOPNZ      LOOPNZD      LOOPNZW      LOOPW        LOOPZ
LOOPZD      LOOPZW      LSL          LSS          LTR
MOV          MOVD        MOVQ        MOVS        MOVSB
MOVSD        MOVSW        MOVSX        MOVZX        MUL
NEG          NOP          NOT          OR          OUT
OUTS        OUTSB        OUTSD        OUTSW        PACKSSDW
PACKSSWB    PACKUSWB    PADDB        PADDD        PADDSB
PADDSW      PADDUSB      PADDUSW      PADDW        PAND
PANDN        PCMPEQB      PCMPEQD      PCMPEQW      PCMPGTB
PCMPGTD      PCMPGTW      PMADDWD      PMULHW      PMULLW
POP          POPA        POPAD        POPD        POPF
POPFD        POPW        POR          PSLLD        PSLLQ
PSLLW        PSRAD        PSRAW        PSRLD        PSRLQ
PSRLW        PSUBB        PSUBD        PSUBSB      PSUBSW
PSUBUSB      PSUBUSW      PSUBW        PUNPCKHBW    PUNPCKHDQ
PUNPCKHWD    PUNPCKLBW    PUNPCKLDQ    PUNPCKLWD    PUSH
PUSHA        PUSHAD      PUSHD        PUSHF        PUSHFD
PUSHW        PXOR        RCL          RCR          RDMSR
RDPMC        RDTSC        REP          REPE        REPNE
REPNZ        REPZ        RET          RETF        RETN
ROL          ROR          RSM          SAHF        SAL
SAR          SBB          SCAS        SCASB        SCASD
SCASW        SETA        SETAE        SETB        SETBE
SETC        SETE        SETG        SETGE        SETL
SETLE        SETNA        SETNAE      SETNB        SETNBE
SETNC        SETNE        SETNG        SETNGE      SETNL
SETNLE      SETNO        SETNP        SETNS        SETNZ
SETO        SETP        SETPE        SETPO        SETS
SETZ        SGDT        SHL          SHLD        SHR
SHRD        SIDT        SLDT        SMSW        STC
STD          STI          STOS        STOSB        STOSD
STOSW        STR          SUB          TEST        UC2
VERR        VERW        WAIT        WBINVD      WRMSR
XADD        XCHG        XLAT        XLATB        XOR </pre>
<br /> <br />


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This is true on pass two.


=== Processor Registers ===
'''Syntax'''


<pre class="western">IF2 </pre>
'''Remarks'''


-----
'''IF2'''does not have an operand.


'''''Processor Registers''are the symbolic names assigned to the various internal processor registers. They are normally used as operands to processor instructions.'''
=== ELSEIFxx/ELSE (Begin Alternate Conditional Block) ===
Each conditional directive can be used with the '''ELSE''' directive to provide the statements to be considered for conditional assembly. The '''ELSE''' directive allows the assembly of the statements following it when the [[#IFxx]] condition or intervening '''ELSEIFxx''' conditions are false.


'''Syntax'''
<pre>
IFxx
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF </pre>
'''Remarks'''


-----
There is a corresponding '''ELSEIFxx''' directive to match all forms of the [[#IFxx]] family of directives:
 
*[[#ELSEIF]]
''Processor-Register'''':'' <br />''General-Purpose-Register'' <br />''Segment-Register'' <br />''Control-Register'' <br />''Debug-Register'' <br />''Test-Register'' <br />''MMX-Register'' <br />''Floating-Point-Register'' <br /> <br />''General-Purpose-Register'''':'' <br />''8-Bit-Register'' <br />''16-Bit-Register'' <br />''32-Bit-Register'' <br /> <br />''8-Bit-Register'''':'' one of <br />'''AL AH BL BH CL CH DL DH''' <br /> <br />''16-Bit-Register'''':'' one of <br />'''AX BX CX DX DI SI BP SP''' <br /> <br />''32-Bit-Register'''':'' one of <br />'''EAX EBX ECX EDX EDI ESI EBP ESP''' <br /> <br />''Segment-Register'''':'' one of <br />'''CS DS ES FS GS SS''' <br /> <br />''Control-Register'''':'' one of <br />'''CR0 CR2 CR3 CR4''' <br /> <br />''Debug-Register'''':'' one of <br />'''DR0 DR1 DR2 DR3 DR4 DR5 DR6 DR7''' <br /> <br />''Test-Register'''':'' one of <br />'''TR3 TR4 TR5 TR6 TR7''' <br /> <br />''MMX-Register'''':'' one of <br />'''MM0 MM1 MM2 MM3 MM4 MM5 MM6 MM7''' <br /> <br />''Floating-Point-Register'''':'' <br />'''ST''' <br /> <br />
*[[#ELSEIFB]]
*[[#ELSEIFDEF]]
*[[#ELSEIFDIF]]
*[[#ELSEIFDIFI]]
*[[#ELSEIFE]]
*[[#ELSEIFIDN]]
*[[#ELSEIFIDNI]]
*[[#ELSEIFNB]]
*[[#ELSEIFNDEF]]
*[[#ELSEIF1]]
*[[#ELSEIF2]]


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For information about the meaning of the conditional tests performed by the '''ELSEIFxx''' directives, refer to the definitions for the corresponding [[#IFxx]] directives.


=== Description ===
Any number of '''ELSEIFxx''' blocks may be used within a given IFxx statement. Only one '''ELSE''' block is permitted for a given IFxx. A conditional directive with more than one '''ELSE''' or an '''ELSE''' without a conditional directive causes an error. '''ELSE''' does not have an operand.


''Processor Registers''are the symbolic names assigned to the various internal processor registers. They are normally used as operands to processor instructions.
'''Note:''' The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.


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'''Example'''
<pre>
IF DEFBUF
  BUF DB 100 DUP(0)
ELSE
  EXTERN BUF:BYTE
ENDIF
</pre>


=== Syntax ===
=== ENDIF (End a Conditional Assembly Statement) ===
'''ENDIF''' ends the conditional assembly statement begun by the corresponding [[#IFxx]] conditional assembly directive. Each IFxx directive must be ended by a matching '''ENDIF''' directive.


''Processor-Register'''':'' <br />''General-Purpose-Register'' <br />''Segment-Register'' <br />''Control-Register'' <br />''Debug-Register'' <br />''Test-Register'' <br />''MMX-Register'' <br />''Floating-Point-Register'' <br /> <br />''General-Purpose-Register'''':'' <br />''8-Bit-Register'' <br />''16-Bit-Register'' <br />''32-Bit-Register'' <br /> <br />''8-Bit-Register'''':'' one of <br />'''AL AH BL BH CL CH DL DH''' <br /> <br />''16-Bit-Register'''':'' one of <br />'''AX BX CX DX DI SI BP SP''' <br /> <br />''32-Bit-Register'''':'' one of <br />'''EAX EBX ECX EDX EDI ESI EBP ESP''' <br /> <br />''Segment-Register'''':'' one of <br />'''CS DS ES FS GS SS''' <br /> <br />''Control-Register'''':'' one of <br />'''CR0 CR2 CR3 CR4''' <br /> <br />''Debug-Register'''':'' one of <br />'''DR0 DR1 DR2 DR3 DR4 DR5 DR6 DR7''' <br /> <br />''Test-Register'''':'' one of <br />'''TR3 TR4 TR5 TR6 TR7''' <br /> <br />''MMX-Register'''':'' one of <br />'''MM0 MM1 MM2 MM3 MM4 MM5 MM6 MM7''' <br /> <br />''Floating-Point-Register'''':'' <br />'''ST''' <br /> <br />
'''Syntax'''
<pre>
IFxx
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF</pre>


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'''Remarks'''


=== Scalar Type Names ===
If the [[#IFxx]] conditional assembly statement is not ended by an '''ENDIF''' directive, an '''unterminated conditional''' message is produced by the assembler. An '''ENDIF''' without a matching IFxx causes an error. '''ENDIF''' does not have an operand.


'''Note:''' The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.


-----
'''Example'''
IF  debug
    EXTERN  dump:FAR
    EXTERN  trace:FAR
    EXTERN  breakpoint:FAR
ENDIF


'''''Scalar Type Names''are the symbolic names given to the integral data types. These are the fundamental types of data upon which the processor can directly operate.'''
=== Text Equate Directives ===
A '''''Text Equate''''' is a symbolic name you give to a series of characters. Text equates are used to expand text within a source statement. The directives described in this section create and manipulate text equates.


EQU <br />CATSTR <br />INSTR <br />SIZESTR <br />SUBSTR


-----
==== CATSTR (Concatenate Strings) ====
'''CATSTR''' concatenates a list of text values specified by ''string'' into a single text value and assigns it to ''Name''.


''Scalar-TypeName'''':'' <br />'''BYTE''' <br />'''SBYTE''' <br />'''WORD''' <br />'''SWORD''' <br />'''DWORD''' <br />'''SDWORD''' <br />'''REAL4''' <br />'''FWORD''' <br />'''QWORD''' <br />'''REAL8''' <br />'''TBYTE''' <br />'''REAL10''' <br /> <br />
'''Syntax'''
Name CATSTR string[, string] ...


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==== EQU Directive (Assign Text to a Symbolic Constant) ====
The '''EQU''' directive assigns the contents of a text literal to ''Name''.


=== Description ===
'''Syntax'''
Name EQU  Text - Literal
'''Remarks'''


''Scalar Type Names''are the symbolic names given to the integral data types. These are the fundamental types of data upon which the processor can directly operate.
The value of the ''Text-Literal'' is assigned to the ''Name'' entry. In normal contexts, subsequent references to ''Name'' will cause the preprocessor to replace ''Name'' with the value specified by the ''Text-Literal'' entry. This is a simple text substitution operation.


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The ''Name'' entry is a globally-scoped ''Identifier'' that is converted to a ''Text-EquateName''. The ''Name'' cannot have been previously defined as a different ''Identifier-Type''. However, the ''Name'' entry can be redefined as many times as desired with different values for the ''Text-Literal'' entry.


=== Syntax ===
See also [[#EQU]] and [[#=]].


''Scalar-TypeName'''':'' <br />'''BYTE''' <br />'''SBYTE''' <br />'''WORD''' <br />'''SWORD''' <br />'''DWORD''' <br />'''SDWORD''' <br />'''REAL4''' <br />'''FWORD''' <br />'''QWORD''' <br />'''REAL8''' <br />'''TBYTE''' <br />'''REAL10''' <br /> <br />
'''Example'''
A  EQU  < BP + >   ; explicit text literal, A is a text equate
A  EQU  < 3 >       ; redefinition of A with different value


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==== INSTR (Search In String For Value) ====
'''INSTR'''searches a specified ''String'' for an occurrence of a given ''Sub-String'' and assigns its position (1-based) to ''Name''. The search is case sensitive. ''Start''is the position in ''String'' to start the search for ''Sub-String''. If ''Start''is not given, it is assumed to be 1 (the start of the string). If ''Sub-String'' is not found, the position assigned to ''Name'' is 0.


=== Distance Type Names ===
'''Syntax'''
Name  INSTR  [ Start , ] String , Sub-String
'''Remarks'''


'''INSTR'''assigns the position value to a name as if it were a numeric equate.


-----
'''Example'''
pos  INSTR  < person > , < son >


'''''Distance Type Names''are the symbolic names given to the integral types of pointers directly supported by the processor. Their names reflect a fundamental property of the Intel processor architecture known as ''distance''. The type of pointer is defined by the ''distance''required to reach the information to which it points.'''
==== SIZESTR (Return Size Of String) ====
Assigns the number of characters given by the ''Text-Argument'' to ''Name''.


'''Syntax'''
Name  SIZESTR  Text-Argument


-----
==== SUBSTR (Extract a Sub-string From a String) ====
Assigns a substring of ''Text-Argument'' starting at ''Position'' to the symbol given by ''Name.''.


''Distance-TypeName'''':'' <br />'''NEAR''' <br />'''NEAR16''' <br />'''NEAR32''' <br />'''FAR''' <br />'''FAR16''' <br />'''FAR32''' <br /> <br />
'''Syntax'''
Name SUBSTR Text-Argument,Position[,Length]


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'''Remarks'''


=== Description ===
The ''Position'' parameter indicates the starting character of the substring to extract from the ''Text-Argument'', and must be 1 or greater. If specified, the ''Length'' parameter indicates how many characters are desired, otherwise the remainder of the string is extracted.


''Distance Type Names''are the symbolic names given to the integral types of pointers directly supported by the processor. Their names reflect a fundamental property of the Intel processor architecture known as ''distance''. The type of pointer is defined by the ''distance''required to reach the information to which it points.
=== Macro Directives ===
'''A macro procedure or function''', which is comprised of one or more statements.


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Macro processing is text processing that is done sequentially at assembly time. By the end of assembly, ALP expands all macros and assembles the resulting text into object code.


=== Syntax ===
This section describes the following types of macros:
* Macro procedures, which expand to one or more complete statements and can optionally take parameters
* Repeat blocks, which generate a group of statements a specified number of times or until a condition becomes true


''Distance-TypeName'''':'' <br />'''NEAR''' <br />'''NEAR16''' <br />'''NEAR32''' <br />'''FAR''' <br />'''FAR16''' <br />'''FAR32''' <br /> <br />
This section describes the following macro directives:
:ENDM
:EXITM
:FOR/IRP
:FORC/IRPC
:LOCAL
:MACRO
:PURGE
:REPEAT/REPT


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==== ENDM (End Current Macro Definition) ====
End each [[#MACRO]], [[#REPEAT/REPT]], [[#FOR/IRP]], and [[#FORC/IRPC]] directive with the '''ENDM'''directive.


=== Language Names ===
;Syntax
ENDM


;Remarks
If the '''ENDM''' directive is not used with the [[#MACRO]], [[#REPEAT/REPT]], [[#FOR/IRP]], and [[#FORC/IRPC]] directives, an error occurs. An unmatched '''ENDM''' also causes an error.


-----
If the assembler produces an error message stating that it found the end-of -file on the source and cannot find an [[#END]] statement when there was an END, the likely cause is a missing '''ENDM''' or ENDIF statement. Without '''ENDM''', the assembler treats the rest of the source as part of the [[#MACRO]] definition.


'''''Language Names''refer to the various high level programming languages (or more specifically, the calling conventions used by such languages) with which the assembler has the ability to interface.'''
'''Note:''' The ''name field'' is not allowed. Do not confuse the '''ENDM''' directive with other ending directives that do require the name of the block being ended, such as ENDP or ENDS.


'''Example'''
addup  MACRO    ad1, ad2, ad3
        MOV      AX, ad1        ;; first parameter in AX
        ADD      AX, ad2        ;; add next two parameters
        ADD      AX, ad3        ;; leave sum in AX
        ENDM


-----
=== EXITM (End Current Macro Expansion) ===
Use the '''EXITM''' directive when a block contains a directive that tests for some condition and you want to end the current macro expansion when the test proves that the remainder of the expansion is not required. When an '''EXITM''' directive is run, the expansion is stopped immediately, and any remaining expansion or repetition is not produced.


''Language-Name'''':'' <br />'''C''' <br />'''SYSCALL''' <br />'''STDCALL''' <br />'''PASCAL''' <br />'''FORTRAN''' <br />'''BASIC''' <br />'''OPTLINK''' <br /> <br />
'''Syntax'''
EXITM


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;Remarks
Only the block containing the '''EXITM''' directive is ended; outer levels of a nested macro expansion continue unaffected.


=== Description ===
'''EXITM''' is executed at macro expansion time and is not a substitute for the [[#ENDM]] directive, which marks the end of the macro body and is recognized at macro definition time.


''Language Names''refer to the various high level programming languages (or more specifically, the calling conventions used by such languages) with which the assembler has the ability to interface.
'''Example'''
<pre>
DSEG  SEGMENT
      .
      .
      .
SYM  =  0
    REPEAT 16
; ; Check for paragraph boundary
      IF  ( $ - DSEG ) MOD 16 EQ 0
      EXITM  ; ; quit if padded to boundary
      ENDIF
SYM = SYM + 1
      DB  SYM  ; ; produce numbered padding
      ENDM </pre>


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=== FOR/IRP (Iterative Macro Expansion Using List of Arguments) ===
The '''FOR''' directive, used in combination with the [[#ENDM]] directive, designates a block of statements to be repeated, once for each argument in the list enclosed by angle brackets. Each repetition substitutes the next item in the <''Argument-List''> entry for every occurrence of ''Parameter'' in the block.


=== Syntax ===
'''Syntax'''
<pre>
FOR  Parameter , < Argument-List >
    .
    .
    .
ENDM</pre>


''Language-Name'''':'' <br />'''C''' <br />'''SYSCALL''' <br />'''STDCALL''' <br />'''PASCAL''' <br />'''FORTRAN''' <br />'''BASIC''' <br />'''OPTLINK''' <br /> <br />
;Remarks
The obsolete spelling for the '''FOR''' directive is '''IRP'''.


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You must enclose the <''Argument-List''> entry in angle brackets. It has the following format:
< [ Argument  [ ,  Argument  . . . ] ] >


=== Anonymous Label Aliases ===
If an empty (<>) ''Argument'' is found in <''Argument-List''>, the ''Parameter'' name is replaced by a null value. If the argument list is empty, the '''FOR'''directive is ignored and no statements are copied. The assembler processes the block once for each ''Argument''in the <''Argument-List''>, replacing each occurrence of ''Parameter''in the macro body with the current ''Argument'' value.


The [[#FOR/IRP]]-[[#ENDM]] block does not have to be within a macro definition.


-----
'''Example'''


The '''''Anonymous Label Aliases''are reserved symbolic names that return a context-sensitive value when referenced in expressions.'''
In this example, the assembler produces the code '''DB'''1 through '''DB'''10.
<pre>FOR    X ,  < 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 >
DB      X
ENDM </pre>
In the next example:
<pre>FOR      ARGUMENT , < " first  line " , 13 , 10 ,
" second  line " , 13 , 10 >
DB      ARGUMENT
ENDM </pre>
The assembler produces the code:
<pre>DB    " first  line "
DB    13
DB    10
DB    " second  line "
DB    13
DB    10 </pre>


The reserved name '''@B'''(backward reference) returns the internally generated name representing the nearest '''@@:'''code label appearing before the current location in the input stream.
=== FORC/IRPC (Iterative Macro Expansion Using List of Characters) ===
The assembler repeats the statements in the block once for each character in the string. Each repetition substitutes the next character in the string for every occurrence of ''Parameter''in the block.


The reserved name '''@F'''(forward reference) returns the internally generated name representing the nearest '''@@:'''code label appearing after the current location in the input stream.
'''Syntax'''
<pre>
FORC  Parameter ,  String ( or < String > )  
    .
    .
    .
ENDM </pre>
'''Remarks'''


The obsolete spelling for the '''FORC'''directive is '''IRPC'''.


-----
The '''FORC'''directive is similar to the [[#FOR/IRP]] directive except that a ''String'' is used instead of <''Argument-List''>, and the angle brackets around the string are optional. The string should be enclosed with angle brackets (<>) if it contains spaces, commas, or other separating characters.


''Anonymous-Label-Alias'''':'' <br />'''@B''' <br />'''@F''' <br /> <br />
The FORC/IRPC-[[#ENDM]] block does not have to be within a macro definition.


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'''Example'''


=== Description ===
In this example, the assembler produces the code '''DB''' 1 through '''DB''' 8:
FORC      X, 12345678
DB        X
ENDM


The '''''Anonymous Label Aliases''are reserved symbolic names that return a context-sensitive value when referenced in expressions.'''
=== LOCAL (Identify Names Local to a Macro Definition) ===
The '''LOCAL''' directive is used inside the body of a macro definition, and provides a method of automatically generating unique assembler labels each time the macro is expanded. The names appearing in the argument list of the '''LOCAL''' directive are known only to the enclosing macro, and each time they are referenced during a macro expansion a unique symbol is created. This prevents the assembler from issuing duplicate definition errors when the macro is expanded more than once and symbols contained therein are being used to create assembler labels.


The reserved name '''@B'''(backward reference) returns the internally generated name representing the nearest '''@@:'''code label appearing before the current location in the input stream.
;Syntax
LOCAL Name [, Name .... ]


The reserved name '''@F'''(forward reference) returns the internally generated name representing the nearest '''@@:'''code label appearing after the current location in the input stream.
;Remarks
The '''LOCAL''' directive is recognized only within the body of a macro given by a [[#MACRO]], [[#FOR/IRP]], [[#FORC/IRPC]], or [[#REPEAT/REPT]] definition. The symbols created by the preprocessor are of the form '''??nnnn''', where '''nnnn''' is a hexadecimal number in the range 0000 through FFFF. You must avoid using identifiers of this form for your own purposes, because doing so can cause duplicate definition errors.


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To insure that they have the proper effect, '''LOCAL''' statements should appear in the body of the macro before any other directives are used. It is acceptable for blank lines or comments to precede any '''LOCAL''' statements.


=== Syntax ===
You can use multiple '''LOCAL''' statements if the argument list is too long to fit on one line, or if you want a vertical list of '''LOCAL''' symbols.


''Anonymous-Label-Alias'''':'' <br />'''@B''' <br />'''@F''' <br /> <br />
;Example
DISPLAY MACRO TT


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; Blank lines and comments are ok here
      LOCAL AGAIN
;; DOS macro to display message addressed by BX TT times
      MOV    CX, TT
      MOV    AH, 9
      MOV    DX, BX
; Generate a unique label for AGAIN
AGAIN:
      INT    21H
      LOOP    AGAIN
      ENDM


=== Location Counter Alias ===
=== MACRO (Assign a Body of Text to a Name) ===
This directive produces a given sequence of statements from various places in your program, even though different parameters may be required each time you call the sequence.


Macro processing consists of two separate and distinct phases: [[#Macro Definition]] and [[#Macro Expansion]].


-----
=== Macro Definition ===
A macro definition consists of three essential parts:
*The '''MACRO''' directive, defining the ''Name'' and the ''Parameter-List''
*The body of the macro, containing the prototypes of statements to produce when you invoke the macro for expansion.
*The [[#ENDM]] directive, ending the definition of the macro.


The '''''Location Counter Alias''is a reserved name used in expressions to return the offset within the current segment or structure being assembled.'''
;Syntax
Name MACRO [Parameter [, Parameter ...]]
  .
  .
  .
ENDM


;Remarks
The ''Name'' field must be a valid preprocessor identifier and specifies the symbolic name that the user will refer to when invoking the macro for expansion. If ''Name'' is already defined, it must be that of a previous macro definition, otherwise an error message is issued. Macros may be redefined to have a different ''Parameter-Lists'' or macro body text; doing so causes the previous definition to be lost.


-----
The optional ''Parameter-List'' is the complete comma-separated list of all ''Parameter'' valuess given in the macro definition statement. A parameter must be a valid symbol name according to the rules for naming preprocessor and assembler identifiers. Each parameter becomes a symbol that is local to the macro being defined and is recognized during macro expansion prior to searching the global name space. Thus, macro parameters need not have names unique from identifiers defined elsewhere in the program.


''Location-Counter-Alias'''':'' <br />'''$''' <br /> <br />
=== Macro Expansion ===
To expand the macro, the macro ''Name'' (defined in the ''Name'' field of the '''MACRO''' definition statement) is coded as you would any other assembler directive, followed by the list of arguments (if any) that you want to pass to the macro.


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;Syntax
Name [Argument [, Argument ...]]


=== Description ===
;Remarks
The ''Name'' field must be the name of a macro defined previously with a '''MACRO''' directive.


The ''Location Counter Alias''is a reserved name used in expressions to return the offset within the current segment or structure being assembled.
Each ''Argument'' field denotes a text value that you want to pass to the macro. The relative positions of the elements are important, because each ''Argument'' is associated in left-to-right fashion with the corresponding ''Parameter'' as defined in the ''Parameter-List'' during the macro definition.


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The number of ''Argument'' entries given when the macro is invoked need not be the same as the number of ''Parameter'' entries. If you pass extra ''Argument''s to the macro, they are ignored; if too few are supplied, empty text values are associated with the remaining ''Parameter''s. You may also associate an empty text value with a ''Parameter'' by passing an explicitly empty text literal <> as an ''Argument''.


=== Syntax ===
Commas are normally used to separate arguments, although blanks or tabs are also considered to be argument separators. For this reason, any argument that must contain an argument separator character (commas, blanks, or tabs) should be enclosed in angle brackets <>. For example:
PUSHVEC  MACRO  PARM1, PARM2
          MOV    AX, PARM1
          PUSH    AX
          MOV    AX, PARM2
          PUSH    AX
          ENDM
          .
          .
          .
          PUSHVEC  DS, <OFFSET VARNAME>
  ; PUSH DWORD VECTOR OF VARNAME ONTO STACK
You can also use angle brackets to produce variable lengths of results. For example:
STRING  MACRO    NUMBERS
          DB        NUMBERS
          ENDM
            .
            .
            .
          STRING  <1,2,3,4>
          ; PRODUCE 4 BYTES OF INTEGER NUMBERS


''Location-Counter-Alias'''':'' <br />'''$''' <br /> <br />
;Remarks
Each time a macro is invoked (expanded) by specifying its name, the preprocessor emits the statements contained in the body of the macro and passes them to the assembler for processing. During the expansion process, any replacement parameters encountered in the macro body (as named in the ''Parameter-List'' of the macro definition) are replaced with the corresponding ''Argument'' (if any) passed through the ''argument-list'' at the time the macro was invoked.


[[[00139.htm|prev]]][[[00141.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
;Example
GEN  MACRO  XX, YY, ZZ
      MOV    AX, XX
      ADD    AX, YY
      MOV    ZZ, AX
      ENDM
When the call is made, for example:
GEN  ED, KISER, SUM
The assembler produces the following code:
MOV    AX, ED
ADD    AX, KISER
MOV    SUM, AX


=== Indeterminate Value Alias ===
=== PURGE (Remove Macro Definition) ===
The '''PURGE''' directive deletes the definition of a specified macro entry, letting you reuse space.


;Syntax
PURGE Macro-Name [, ...]


-----
;Remarks
It is not necessary to purge a macro before redefining it. You may use '''PURGE''' to recover memory during assembly by deleting the contents of unreferenced macros. An '''Out of Memory''' condition can occur if a large, general-purpose macro library is included.


The '''''Indeterminate Value Alias''is a reserved name used in expressions to represent an uninitialized value.'''
;Example
The directive:
PURGE    MACRONAME


performs the same function as redefining the macro with no contents, as in:
MACRONAME MACRO
          ENDM


-----
In the following example, assume that MAC1 is a macro included in MACRO.LIB:
INCLUDE  MACRO.LIB
PURGE    MAC1
MAC1      ; Calls the purged macro
          ; but produces nothing


''Indeterminate-Value-Alias'''':'' <br />'''?''' <br /> <br />
=== REPEAT/REPT (Iterative Macro Expansion Using a Count Expression) ===
'''REPEAT''' specifies the number of times to generate the statements inside the macro.


[[[00140.htm|prev]]][[[00142.htm|next]]][[[00140.htm|parent]]][[[toc.htm|TOC]]]<br />
;Syntax
REPEAT Expression
  Statements
ENDM


=== Description ===
;Remarks
The ''Expression'' field must evaluate to an ''Absolute-ExpressionType'' (it cannot contain forward references). Because the repeat block will be expanded at assembler time, the number of iterations must be known then.


The ''Indeterminate Value Alias''is a reserved name used in expressions to represent an uninitialized value.
=== ECHO Directive (Display Message on Standard Output Device) ===
The '''ECHO''' directive displays progress through a long assembly or displays the value of conditional assembly parameters.


[[[00141.htm|prev]]][[[00143.htm|next]]][[[00140.htm|parent]]][[[toc.htm|TOC]]]<br />
'''Syntax'''
ECHO Text
'''Remarks'''


=== Syntax ===
The assembler lists the ''Text'' entry on the standard output device during assembly when the assembler encounters the '''ECHO''' directive.


''Indeterminate-Value-Alias'''':'' <br />'''?''' <br /> <br />
'''ECHO''' is not available under MASM 5.10 emulation; you must use '''%OUT,''' which is the obsolete spelling for the '''ECHO''' directive.


[[[00142.htm|prev]]][[[00144.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
'''Example'''


=== Directive Keywords ===
'''Example 1:'''
IF IBM
  ECHO IBM VERSION
ENDIF


IF2
  ECHO STARTING SECOND PASS
    .
    .
    .
  ENDIF


-----
'''Example 2:'''
INNER  MACRO    TEXT, VAL
        ECHO    TEXT  VAL
        ENDM
        .
        .
        .
HERE    =  $ - CSEG
        INNER <CURRENT LOCATION>,%HERE


'''''Directive Keywords''are symbolic names recognized and used in the body of various assembler directives.'''
=== INCLUDE Directive (Insert File Contents into Input Stream) ===
The '''INCLUDE''' directive "stacks" the current source file and begins reading tokens from the source file given by the ''FileName'' argument. If you use the '''INCLUDE''' directive, you need not repeat a sequence of statements that are common to several source files.


'''Syntax'''
INCLUDE FileName
'''Remarks'''


-----
The assembler uses the following search order when attempting to open the '''INCLUDE''' file:
# If the  ''FileName'' argument contains a fully qualified path name (one that begins with a back slash or forward slash), then the assembler attempts to open the file exactly as specified, and no other search is performed if the file is not found.
# If the ''FileName'' begins with a relative path name or contains no path information, the assembler begins searching for the '''INCLUDE''' file by looking in the directory of the source file that issued the '''INCLUDE''' directive.
# The assembler searches for ''FileName'' in the list of directories given by any [[#-Fdi]] or [[#-I]] options found on the command line.
# The assembler searches for ''FileName'' in the list of directories given by the <BaseEXE>_INCLUDE environment variable.
# The assembler searches for ''FileName'' in the list of directories given by the INCLUDE environment variable.
# Lastly, the assembler searches for ''FileName'' in the current directory. If the named file is not found, the assembler issues a fatal error message and the assembler is ended.


''Directive-Keyword'''':'' <br />'''<br />'''
In no case does the assembler strip relative path information from the ''FileName'' when performing search steps 2 through 6.


<pre>ABS        AT            BASIC        C
When the file named in the '''INCLUDE''' directive is located, the assembler opens it and assembles all of the statements contained therein until the end of the file is reached. The file is then closed and assembler resumes in the original module at the line following the '''INCLUDE''' directive.
CASEMAP    CODE          COMMON        DOTNAME
EMULATOR    EPILOGUE      ERROR        EXPORT
EXPR16      EXPR32        FARSTACK      FLAT
FORTRAN    HUGE          LANGUAGE      LARGE
LJMP        MEDIUM        NEARSTACK    NODOTNAME
NOEMULATOR  NOKEYWORD    NOLANGUAGE    NOLJMP
NONE        NOOLDMACROS  NOOLDSTRUCTS  NOREADONLY
NOSCOPED    NOSIGNEXTEND  NOTHING      NOTPUBLIC
OLDMACROS  OLDSTRUCTS    OPTLINK      OS_DOS
OS_OS2      PAGE          PARA          PASCAL
PRIVATE    PROC          PROLOGUE      PUBLIC
READONLY    SCOPED        SEGMENT      SIGNEXTEND
SMALL      STACK        STDCALL      SYSCALL
TINY        USE16        USE32        USES</pre>
<br /> <br />


[[[00143.htm|prev]]][[[00145.htm|next]]][[[00143.htm|parent]]][[[toc.htm|TOC]]]<br />
An '''INCLUDE''' file should not contain an [[#END]] assembler directive to denote the end of the included module; the assembler closes the included module when its physical end of file is reached.


=== Description ===
'''INCLUDE''' files may be nested to any reasonable level, and is limited only by the operating system's ability to provide the necessary resources.


''Directive Keywords''are symbolic names recognized and used in the body of various assembler directives.
;Example
INCLUDE OS2.INC


[[[00144.htm|prev]]][[[00146.htm|next]]][[[00143.htm|parent]]][[[toc.htm|TOC]]]<br />
=== COMMENT Directive (Program Information Block) ===
'''COMMENT''' lets you enter comments about your program without having to enter semicolons (;) for each line.


=== Syntax ===
;Syntax
COMMENT  Delimiter  Text  Delimiter


''Directive-Keyword'''':'' <br />'''<br />'''
;Remarks
The first non-blank character after '''COMMENT''' is the first delimiter. The '''COMMENT''' directive causes the assembler to treat all ''Text'' between ''Delimiter'' and ''Delimiter'' as a comment. The text must not contain the delimiter character. This directive is used for multiple-line comments. A '''COMMENT''' defined in the body of a macro does not appear unless '''.LALL''' is requested.


<pre>ABS        AT            BASIC        C
'''Example'''
CASEMAP    CODE          COMMON        DOTNAME
COMMENT *You can enter as many lines
EMULATOR    EPILOGUE      ERROR        EXPORT
of text between the delimiters
EXPR16      EXPR32        FARSTACK      FLAT
    .
FORTRAN    HUGE          LANGUAGE      LARGE
    .
LJMP        MEDIUM        NEARSTACK    NODOTNAME
    .
NOEMULATOR  NOKEYWORD    NOLANGUAGE    NOLJMP
as you need to describe your program.*
NONE        NOOLDMACROS  NOOLDSTRUCTS  NOREADONLY
NOSCOPED    NOSIGNEXTEND  NOTHING      NOTPUBLIC
OLDMACROS  OLDSTRUCTS    OPTLINK      OS_DOS
OS_OS2      PAGE          PARA          PASCAL
PRIVATE    PROC          PROLOGUE      PUBLIC
READONLY    SCOPED        SEGMENT      SIGNEXTEND
SMALL      STACK        STDCALL      SYSCALL
TINY        USE16        USE32        USES</pre>
<br /> <br />
 
[[[00145.htm|prev]]][[[00147.htm|next]]][[[00110.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operator Keywords ===
 
 
-----
 
'''''Operator Keywords''are symbolic names used in expressions to denote an operation to be performed on one or more operands.'''
 
 
-----
 
''Operator-Keyword'''':'' <br />'''<br />'''
 
<pre>AND        DUP        EQ          GE
GT          HIGH        HIGHWORD    LE
LENGTH      LENGTHOF    LOW        LOWWORD
LT          MASK        MOD        NE
NOT        OFFSET      OPATTR      OR
PTR        SEG        SHL        SHORT
SHR        SIZE        SIZEOF      THIS
.TYPE      TYPE        WIDTH      XOR</pre>
<br /> <br />
 
[[[00146.htm|prev]]][[[00148.htm|next]]][[[00146.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
''Operator Keywords''are symbolic names used in expressions to denote an operation to be performed on one or more operands.
 
[[[00147.htm|prev]]][[[00149.htm|next]]][[[00146.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Operator-Keyword'''':'' <br />'''<br />'''
 
<pre>AND        DUP        EQ          GE
GT          HIGH        HIGHWORD    LE
LENGTH      LENGTHOF    LOW        LOWWORD
LT          MASK        MOD        NE
NOT        OFFSET      OPATTR      OR
PTR        SEG        SHL        SHORT
SHR        SIZE        SIZEOF      THIS
.TYPE      TYPE        WIDTH      XOR</pre>
<br /> <br />
 
[[[00148.htm|prev]]][[[00150.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Identifiers ===
 
 
-----
 
This section describes the syntax for identifiers and the various types of information they can be made to represent.
 
 
-----
 
''Identifier'''':'' <br />''Normal-Identifier'' <br />''Dot-Identifier'' <br /> <br />''Normal-Identifier'' <br />''NonDigit'' <br />''Normal-Identifier Identifer-Character'' <br /> <br />''Dot-Identifier'' <br />''. Normal-Identifier'' <br /> <br />''Identifier-Character'' <br />''NonDigit'' <br />''Digit'' <br /> <br />''NonDigit:'' one of <br />'''<br />'''
 
<pre> _ $ @ ?
 
a b c d e f g h i j k l m
 
n o p q r s t u v w x y z
 
A B C D E F G H I J K L M
 
N O P Q R S T U V W X Y Z
</pre>
<br />''Digit:'' one of <br />'''<br />'''
 
<pre> 0 1 2 3 4 5 6 7 8 9
</pre>
<br /> <br />
 
[[[00149.htm|prev]]][[[00151.htm|next]]][[[00149.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
This section describes the syntax for identifiers and the various types of information they can be made to represent.
 
[[[00150.htm|prev]]][[[00152.htm|next]]][[[00149.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Identifier'''':'' <br />''Normal-Identifier'' <br />''Dot-Identifier'' <br /> <br />''Normal-Identifier'' <br />''NonDigit'' <br />''Normal-Identifier Identifer-Character'' <br /> <br />''Dot-Identifier'' <br />''. Normal-Identifier'' <br /> <br />''Identifier-Character'' <br />''NonDigit'' <br />''Digit'' <br /> <br />''NonDigit:'' one of <br />'''<br />'''
 
<pre> _ $ @ ?
 
a b c d e f g h i j k l m
 
n o p q r s t u v w x y z
 
A B C D E F G H I J K L M
 
N O P Q R S T U V W X Y Z
</pre>
<br />''Digit:'' one of <br />'''<br />'''
 
<pre> 0 1 2 3 4 5 6 7 8 9
</pre>
<br /> <br />
 
[[[00151.htm|prev]]][[[00153.htm|next]]][[[00149.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Identifier Types ===
 
 
-----
 
This section describes the various types of identifiers that the assembler will create and manipulate.
 
 
-----
 
''Identifier-Type'''':'' <br />[[00155.htm|''EquateName'']] <br />[[00158.htm|''FieldName'']] <br />[[00162.htm|''GroupName'']] <br />[[00163.htm|''LabelName'']] <br />[[00168.htm|''MacroName'']] <br />[[00170.htm|''SegmentName'']] <br />[[00171.htm|''UserDefined-TypeName'']] <br /> <br />
 
[[[00152.htm|prev]]][[[00154.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
This section describes the various types of identifiers that the assembler will create and manipulate.
 
[[[00153.htm|prev]]][[[00155.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Definition ===
 
''Identifier-Type'''':'' <br />[[00155.htm|''EquateName'']] <br />[[00158.htm|''FieldName'']] <br />[[00162.htm|''GroupName'']] <br />[[00163.htm|''LabelName'']] <br />[[00168.htm|''MacroName'']] <br />[[00170.htm|''SegmentName'']] <br />[[00171.htm|''UserDefined-TypeName'']] <br /> <br />
 
[[[00154.htm|prev]]][[[00156.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Equate Name ===
 
'''Definition'''
 
''EquateName'''':'' <br />[[00156.htm|''Numeric-EquateName'']] <br />[[00157.htm|''Text-EquateName'']] <br />
 
'''Description'''
 
An ''EquateName''is a symbolic identifier that is associated with an expression or a body of text. The assembler substitutes the value of the ''EquateName''at the point of reference. <br />
 
[[[00155.htm|prev]]][[[00157.htm|next]]][[[00155.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Numeric Equate Name ===
 
An identifier becomes a ''Numeric-EquateName''when it is defined in a [[00791.htm|EQU]]or [[00786.htm|=]] directive. Procedure [[00742.htm|parameter]]names and [[00743.htm|local variable]]names are also created as ''Numeric-EquateName''''s'', but are visible only from within the procedure where they are defined. All other ''Numeric-EquateName''''s''are globally-scoped identifiers visible across the entire module.
 
A ''Numeric-EquateName''may only be referenced from within [[00254.htm|expressions]], as its replacement value is itself an expression.
 
[[[00156.htm|prev]]][[[00158.htm|next]]][[[00155.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Equate Name ===
 
A ''Text-EquateName''is a globally-scoped identifier created during the processing of a [[00683.htm|EQU]]preprocessor directive. A ''Text-EquateName''is associated with a body of text whose content may not span across line breaks. In certain contexts the assembler replaces the ''Text-EquateName'' with the text that it represents and recursively evaluates the result.
 
[[[00157.htm|prev]]][[[00159.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Field Name ===
 
'''Definition'''
 
''FieldName'''':'' <br />[[00159.htm|''Record-FieldName'']] <br />[[00160.htm|''Structure-FieldName'']] <br />[[00161.htm|''Union-FieldName'']] <br />
 
'''Description'''
 
An identifier becomes a ''FieldName''when it is defined within a [[00781.htm|RECORD]], [[00782.htm|STRUCT]], or [[00784.htm|UNION]]directive. <br />
 
[[[00158.htm|prev]]][[[00160.htm|next]]][[[00158.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Record Field Name ===
 
A ''Record-FieldName''is a globally-scoped identifier created during the processing of a [[00781.htm|RECORD]]directive. It is a special variation of a [[00156.htm|''Numeric- EquateName'']]and can be used in the same contexts.
 
[[[00159.htm|prev]]][[[00161.htm|next]]][[[00158.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Structure Field Name ===
 
An identifier becomes a ''Structure-FieldName''when it is defined in a [[00782.htm|STRUCT]] directive. If the assembler is operating in [[00105.htm|M510]]mode, or if the [[00793.htm|OPTION OLDSTRUCTS]]directive has been specified, then a ''Structure-FieldName''is a globally-scoped identifier treated as a special variation of a [[00156.htm|''Numeric- EquateName'']]and can be used in the same contexts. Otherwise, a ''Structure- FieldName''is private to the defining structure and is only accessible in expressions through use of the [[00482.htm|Structure/Union Field Selection (. Operator)]] .
 
[[[00160.htm|prev]]][[[00162.htm|next]]][[[00158.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Union Field Name ===
 
An identifier becomes a ''Union-FieldName''when it is defined in a [[00784.htm|UNION]] directive. A ''Union-FieldName''is private to the defining union and is only accessible in expressions through use of the [[00482.htm|Structure/Union Field Selection (. Operator)]].
 
[[[00161.htm|prev]]][[[00163.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Group Name ===
 
A ''GroupName''is a globally-scoped identifier created during the processing of a [[00774.htm|GROUP]]directive. It is referenced from within expressions.
 
[[[00162.htm|prev]]][[[00164.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Label Name ===
 
'''Definition'''
 
''LabelName'''':'' <br />[[00164.htm|''Code-LabelName'']] <br />[[00167.htm|''Data-LabelName'']] <br />
 
'''Description'''
 
A ''LabelName''is globally-scoped identifier that is associated with a program address at application run-time. It has an explicit or inherited [[00250.htm|''Type-Declaration'']], and an optional ''Language-Attribute''. These attributes are described in the following sections.
 
 
 
'''Type Declaration'''
 
The type declaration associated with a label name depends on how the label was defined. See the [[00164.htm|''Code-LabelName'']]and [[00167.htm|''Data-LabelName'']]sections for descriptions on how this attribute is assigned.
 
 
 
'''Language Attribute'''
 
A ''LabelName''can have an assigned ''Language-Attribute'', set either implicitly through the use of a [[00131.htm|''Language-Name'']]keyword in the body of a [[00775.htm|.MODEL]]or [[00793.htm|OPTION]]directive, or explicitly through the use of an overriding [[00131.htm|''Language- Name'']]keyword in the body of a [[00716.htm|EXTERN/EXTRN]], [[00717.htm|EXTERNDEF]], [[00739.htm|PROC]], or [[00720.htm|PUBLIC]] directive. The ''Language-Attribute''determines the exact spelling of the ''LabelName''identifier when it is written to the object file. According to the ''Language-Attribute'', identifier spellings are modified from their appearance in the assembly language source module as follow: <br />
 
<pre>/-----------------------------------------------------------\
|LANGUAGE ATTRIBUTE|IDENTIFIER SPELLING                    |
|------------------+----------------------------------------|
|OPTLINK, SYSCALL  |No modifications are made to the        |
|                  |identifier when written to the object  |
|                  |file.                                  |
|------------------+----------------------------------------|
|C, STDCALL        |A leading underscore character is      |
|                  |appended to the front of the name.      |
|------------------+----------------------------------------|
|BASIC, FORTRAN,  |All characters in the identifier are    |
|PASCAL            |converted to uppercase.                |
\-----------------------------------------------------------/</pre>
<br />
 
[[[00163.htm|prev]]][[[00165.htm|next]]][[[00163.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Code Label Name ===
 
'''Definition'''
 
''Code-LabelName'''':'' <br />[[00165.htm|''Target-LabelName'']] <br />[[00166.htm|''Procedure-LabelName'']] <br />
 
'''Description'''
 
A ''Code-LabelName''is an identifier that is associated with an executable code address at application run-time. There are two types of ''Code- LabelName''''s'''':''[[00165.htm|''Target-LabelName'']]''s''and [[00166.htm|''Procedure-LabelName'']]''s''. <br />
 
[[[00164.htm|prev]]][[[00166.htm|next]]][[[00164.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Target Label Name ===
 
An identifier becomes a ''Target-LabelName''when it is defined with a [[00792.htm|:]], [[00792.htm|::]], or [[00792.htm|LABEL]]directive.
 
If a ''Target-LabelName''created with a single colon (:) is defined within the body of a [[00739.htm|procedure]], then the name is visible only from within that procedure unless operating in [[00105.htm|M510]]mode (and no [[00775.htm|.MODEL]]directive with a [[00131.htm|''Language-Name'']]has been specified), or unless the [[00793.htm|OPTION NOSCOPED]]directive has been specified.
 
A ''Target-LabelName''defined outside the body of a procedure is visible to the entire module, and may also be given [[00720.htm|PUBLIC]]visibility.
 
[[[00165.htm|prev]]][[[00167.htm|next]]][[[00164.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Procedure Label Name ===
 
An identifier becomes a ''Procedure-LabelName''when it is defined in a '''PROC''' directive.
 
[[[00166.htm|prev]]][[[00168.htm|next]]][[[00163.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Data Label Name ===
 
A ''Data-LabelName''is an identifier that is the address of a program variable at application run-time. An identifier becomes a ''Data-LabelName''when it is named in a data allocation statement, or when a scalar, aggregate, or vector type is associated with the identifier named in a [[00792.htm|LABEL]], [[00716.htm|EXTERN/ EXTRN]], [[00717.htm|EXTERNDEF]], or [[00714.htm|COMM]]directive.
 
[[[00167.htm|prev]]][[[00169.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Macro Name ===
 
A ''MacroName''is a globally-scoped identifier created during the processing of a '''MACRO'''directive. It is associated with a multi-line body of text. A ''MacroName''may only be used in contexts where a normal assembler directive is expected.
 
[[[00168.htm|prev]]][[[00170.htm|next]]][[[00168.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Macro Parameter Name ===
 
An identifier becomes a ''Macro-ParameterName''when it is named as a parameter to a macro in a '''MACRO'''directive. It is associated with a body of text whose content may not span across line breaks. It is only recognized and acted upon from within the body of a macro expansion.
 
[[[00169.htm|prev]]][[[00171.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Segment Name ===
 
A ''SegmentName''is a globally-scoped identifier created during the processing of a [[00777.htm|SEGMENT]]directive. It may be referenced from within expressions or in the body of a [[00774.htm|GROUP]]directive.
 
[[[00170.htm|prev]]][[[00172.htm|next]]][[[00152.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== User-Defined Type Name ===
 
'''Definition'''
 
''UserDefined-TypeName'''':'' <br />[[00172.htm|''Record-TypeName'']] <br />[[00173.htm|''Structure-TypeName'']] <br />[[00174.htm|''Typedef-TypeName'']] <br />[[00175.htm|''Union-TypeName'']] <br />
 
'''Description'''
 
An identifier becomes a ''UserDefined-TypeName''when it is defined within a [[00781.htm|RECORD]], [[00782.htm|STRUCT]], [[00783.htm|TYPEDEF]], or [[00784.htm|UNION]]directive. <br />
 
[[[00171.htm|prev]]][[[00173.htm|next]]][[[00171.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Record Type Name ===
 
A ''Record-TypeName''is a globally-scoped identifier created during the processing of a [[00781.htm|RECORD]]directive. It is recognized from within [[00255.htm|''Expression'']]''s'' , [[00250.htm|''Type-Declaration'']]''s'', or as a pseudo-directive in a [[00709.htm|data allocation statement]].
 
[[[00172.htm|prev]]][[[00174.htm|next]]][[[00171.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Structure Type Name ===
 
A ''Structure-TypeName''is a globally-scoped identifier created during the processing of a [[00782.htm|STRUCT]]directive. It is recognized from within [[00255.htm|''Expression'']]''s'' , [[00250.htm|''Type-Declaration'']]''s'', or as a pseudo-directive in a [[00709.htm|data allocation statement]].
 
[[[00173.htm|prev]]][[[00175.htm|next]]][[[00171.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Typedef Type Name ===
 
A ''Typedef-TypeName''is a globally-scoped identifier created during the processing of a [[00783.htm|TYPEDEF]]directive. It is recognized from within [[00255.htm|''Expression'']]''s'', [[00250.htm|''Type-Declaration'']]''s'', or as a pseudo-directive in a [[00709.htm|data allocation statement]].
 
[[[00174.htm|prev]]][[[00176.htm|next]]][[[00171.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Union Type Name ===
 
A ''Union-TypeName''is a globally-scoped identifier created during the processing of a [[00784.htm|UNION]]directive. It is recognized from within [[00255.htm|''Expression'']]''s'', [[00250.htm|''Type-Declaration'']]''s'', or as a pseudo-directive in a [[00709.htm|data allocation statement]].
 
[[[00175.htm|prev]]][[[00177.htm|next]]][[[00149.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Predefined Identifiers ===
 
The following sections describe the predefined identifiers created by the assembler. When a case-sensitive assembly is being performed, the predefined identifiers must be spelled exactly as they appear in the following descriptions with respect to uppercase and lowercase characters.
 
[[[00176.htm|prev]]][[[00178.htm|next]]][[[00176.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Segment Information ===
 
The following sections describe the predefined identifiers created by the assembler in support of segment manipulation.
 
[[[00177.htm|prev]]][[[00179.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @code ===
 
The '''@code'''identifier is a [[00157.htm|''Text-EquateName'']]created by the assembler when a [[00775.htm|. MODEL]]directive is encountered, at which time the assembler performs an automatic '''ASSUME CS:'''@code''''''operation. The '''@code'''symbol is not defined if a [[00775.htm|.MODEL]]directive has not been issued.
 
Under MASM 5.10 emulation, the '''@code'''symbol is set to the name of the implicitly-defined default code segment (the segment opened when a [[00765.htm|.CODE]] directive is used) and its value is never changed. In other modes, the '''@ code'''symbol is updated to reflect whatever segment is opened by using [[00765.htm|.CODE]] , whether defined implicitly or as an explicit parameter to the [[00765.htm|.CODE]] directive.
 
The value assigned to the '''@code'''symbol when the default code segment is opened is determined by the memory model as follows:
 
'''Memory Model''''''Value for @code''' <br />TINY DGROUP <br />SMALL _TEXT <br />MEDIUM ''module''_TEXT <br />COMPACT_TEXT <br />LARGE ''module''_TEXT <br />HUGE ''module''_TEXT <br />FLAT CODE32 <br />
 
The ''module''entry is replaced with base file name of the top-level module being assembled.
 
[[[00178.htm|prev]]][[[00180.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @CodeSize ===
 
The '''@CodeSize'''identifier is a [[00156.htm|''Numeric-EquateName'']]created by the assembler when a [[00775.htm|.MODEL]]directive is encountered. '''@CodeSize'''indicates whether code segments created by the [[00765.htm|.CODE]]directive are named such that the linker will combine them into a single (NEAR) segment or into multiple (FAR) segments. The '''@CodeSize'''symbol is set to 0 (NEAR) for the '''TINY, SMALL, COMPACT,'''and '''FLAT'''memory models, and to 1 (FAR) for the '''MEDIUM, LARGE,'''and '''HUGE'''memory models. The '''@CodeSize'''symbol is not defined if a [[00775.htm|.MODEL]]directive has not been issued.
 
[[[00179.htm|prev]]][[[00181.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @CurSeg ===
 
The '''@CurSeg'''identifier is a [[00157.htm|''Text-EquateName'']]defined by the assembler to hold the name of the currently opened segment. If no segment is currently open, '''@CurSeg'''will expand into an empty string.
 
[[[00180.htm|prev]]][[[00182.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @data ===
 
The '''@data'''identifier is a [[00157.htm|''Text-EquateName'']]created by the assembler when a [[00775.htm|. MODEL]]directive is encountered. It expands to the group name shared by all of the near data segments. If a '''.MODEL FLAT'''has been issued, the '''@data''' identifier expands to FLAT. For all other memory models, it expands to DGROUP.
 
[[[00181.htm|prev]]][[[00183.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @DataSize ===
 
The '''@DataSize'''identifier is a [[00156.htm|''Numeric-EquateName'']]created by the assembler when a [[00775.htm|.MODEL]]directive is encountered, and represents the default data distance. Depending on the currently selected memory model, the '''@DataSize''' identifier is set to the following values: ''''''
 
<br />TINY 0 <br />SMALL 0 <br />COMPACT1 <br />MEDIUM 1 <br />LARGE 1 <br />HUGE 2 <br />FLAT 0 <br />
 
[[[00182.htm|prev]]][[[00184.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Model ===
 
The '''@Model'''identifier is a [[00156.htm|''Numeric-EquateName'']]created by the assembler when a [[00775.htm|.MODEL]]directive is encountered, and is set to a unique value for each memory model. The values are as follows: ''''''
 
<br />TINY 1 <br />SMALL 2 <br />COMPACT3 <br />MEDIUM 4 <br />LARGE 5 <br />HUGE 6 <br />FLAT 7 <br />
 
[[[00183.htm|prev]]][[[00185.htm|next]]][[[00177.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @WordSize ===
 
The '''@WordSize'''identifier is a [[00156.htm|''Numeric-EquateName'']]that reflects the address size attribute of the current segment. It is set to 2 for a '''USE16'''segment, and 4 for a '''USE32'''segment. If no segment is currently open, it reflects the default address size as determined by the currently selected processor.
 
[[[00184.htm|prev]]][[[00186.htm|next]]][[[00176.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Version Information ===
 
These identifiers offer methods of testing the various operating modes of the assembler to determine what features are activated or disabled, or how the assembler will behave under various conditions.
 
[[[00185.htm|prev]]][[[00187.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Alp ===
 
The '''@Alp'''identifier is a [[00157.htm|''Text-EquateName'']]that can be tested to determine if ALP is assembling the source file (versus some other assembler). It is always set to the string '''100'''.
 
[[[00186.htm|prev]]][[[00188.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @AlpMajor ===
 
The '''@AlpMajor'''identifier is a [[00157.htm|''Text-EquateName'']]that reflects the ''major'' portion of the three-part assembler version number. It is padded on the right with zeros to allow major version number comparisions independant of the minor version and revisions numbers. See [[00190.htm|@AlpVersion]]for more information.
 
This identifier is only defined in [[00105.htm|ALP]]mode.
 
[[[00187.htm|prev]]][[[00189.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @AlpMinor ===
 
The '''@AlpMinor'''identifier is a [[00157.htm|''Text-EquateName'']]that reflects the ''minor'' portion of the three-part assembler version number. It is padded on the right with zeros to allow minor version number comparisions independant of the major version and revisions numbers. See [[00190.htm|@AlpVersion]]for more information.
 
This identifier is only defined in [[00105.htm|ALP]]mode.
 
[[[00188.htm|prev]]][[[00190.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @AlpRevision ===
 
The '''@AlpRevision'''identifier is a [[00157.htm|''Text-EquateName'']]that reflects the ''revision'' portion of the three-part assembler version number. It allows revision number comparisions independant of the major and minor version numbers. See [[00190.htm|@AlpVersion]]for more information.
 
This identifier is only defined in [[00105.htm|ALP]]mode.
 
[[[00189.htm|prev]]][[[00191.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @AlpVersion ===
 
The '''@AlpVersion'''identifier is a [[00157.htm|''Text-EquateName'']]that reflects the full three-part assembler version number. This is an encoding of the version number printed in the program banner when the assembler is invoked. This number and its requisite parts may be tested to determine the presence or absence of features provided by the assembler.
 
The assembler version number consists of three parts:
 
1.The major version number (one digit) <br /> 2.The minor version number (two digits) <br /> 3.The revision number (three digits) <br />
 
In the assembler banner, the numbers are separated by the period (.) character; the period is removed from the text defined by the predefined identifiers.
 
For example, if the major version number is '''1''', the minor version number is '''2''', and the revision number is '''3''', then the full version number is printed in the assembler banner as '''1.02.003''', and the various predefined version identifers would be set as follows: '''<br />'''
 
<pre>    @AlpVersion  102003
    @AlpMajor    100000
    @AlpMinor      2000
    @AlpRevision    003</pre>
This identifier is only defined in [[00105.htm|ALP]]mode.
 
[[[00190.htm|prev]]][[[00192.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Cpu ===
 
The '''@Cpu'''identifier is a [[00156.htm|''Numeric-EquateName'']]that reflects the currently selected processor for which ALP is assembling instructions. This value is affected by issuing a [[00745.htm|''Processor-Control-Directive'']], and is a bit map that indicates the currently active processor instruction set(s). <br />
 
<pre>/------------------------------------------------------\
|B|A|9|8|7|6|5|4|3|2|1|0|BIT SET IF ASSEMBLING FOR:    |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | | | | | | |1|8086/8088                    |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | | | | | |1| |80186                        |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | | | | |1| | |80286                        |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | | | |1| | | |80386                        |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | | |1| | | | |80486                        |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | | |1| | | | | |80586 (Pentium)              |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | | |1| | | | | | |80686 (Pentium Pro)          |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | | |1| | | | | | | |Privileged mode              |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | | |1| | | | | | | | |8087                          |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| | |1| | | | | | | | | |MMX Extensions                |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
| |1| | | | | | | | | | |80287                        |
|-+-+-+-+-+-+-+-+-+-+-+-+------------------------------|
|1| | | | | | | | | | | |80387                        |
\------------------------------------------------------/</pre>
[[[00191.htm|prev]]][[[00193.htm|next]]][[[00185.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Version ===
 
The '''@Version'''identifier is a [[00157.htm|''Text-EquateName'']]that reflects the MASM- compatible version number. The current emulation mode of the assembler affects the value of this symbol as follows:
 
<br />[[00105.htm|M510]]510 <br />[[00105.htm|M600]]600 <br />[[00105.htm|ALP]]4294967295 (the highest possible value for an unsigned 32-bit integer) <br />
 
[[[00192.htm|prev]]][[[00194.htm|next]]][[[00176.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Date and Time Information ===
 
These identifiers allow the programmer to query the system date or time during the assembly. Each time they are referenced, a new system request for the current date and time is made and the values held in the identifiers are refreshed.
 
[[[00193.htm|prev]]][[[00195.htm|next]]][[[00193.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Date ===
 
The '''@Date'''identifier is a [[00157.htm|''Text-EquateName'']]that is set to the current system date. If the current operating mode is [[00105.htm|M600]], the date is returned in the MM/DD/YY format. In native [[00105.htm|ALP]]mode, the date is returned in the MM/DD/ YYYY format.
 
The '''@Date'''identifier is not available in [[00105.htm|M510]]mode.
 
[[[00194.htm|prev]]][[[00196.htm|next]]][[[00193.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Time ===
 
The '''@Time'''identifier is a [[00157.htm|''Text-EquateName'']]that is set to the current system time in 24-hour HH:MM:SS format.
 
The '''@Time'''identifier is not available in [[00105.htm|M510]]mode.
 
[[[00195.htm|prev]]][[[00197.htm|next]]][[[00176.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== File Information ===
 
These identifiers return information about the file(s) being assembled.
 
[[[00196.htm|prev]]][[[00198.htm|next]]][[[00196.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @FileName ===
 
The '''@FileName'''identifier is a [[00157.htm|''Text-EquateName'']]that is set to the base name of the main file being assembled (as it appears on the command line).
 
[[[00197.htm|prev]]][[[00199.htm|next]]][[[00196.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== @Line ===
 
The '''@Line'''identifier is a [[00156.htm|''Numeric-EquateName'']]that is set to the current source line number in the file currently being assembled.
 
The '''@Line'''identifier is not available in [[00105.htm|M510]]mode.
 
[[[00198.htm|prev]]][[[00200.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Literals ===
 
 
-----
 
'''''Literals''are the notational method whereby numeric values or strings of character data are represented in the source stream. Literals are also commonly referred to as '''''constants''(especially in the context of high level languages) because they typically represent objects whose values do not change throughout the life of the assembly or compilation. However, literals should not be confused with run-time &quot;constants&quot; (&quot;read-only&quot; data items allocated by the programmer); they are assembly-time tokens used by the assembler to represent numeric values or character strings.''''''
 
 
-----
 
''Literal'''':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />
 
[[[00199.htm|prev]]][[[00201.htm|next]]][[[00199.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
''Literals''are the notational method whereby numeric values or strings of character data are represented in the source stream. Literals are also commonly referred to as ''constants''(especially in the context of high level languages) because they typically represent objects whose values do not change throughout the life of the assembly or compilation. However, literals should not be confused with run-time &quot;constants&quot; (&quot;read-only&quot; data items allocated by the programmer); they are assembly-time tokens used by the assembler to represent numeric values or character strings.
 
[[[00200.htm|prev]]][[[00202.htm|next]]][[[00199.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Literal'''':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />
 
[[[00201.htm|prev]]][[[00203.htm|next]]][[[00199.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Integer Literals ===
 
 
-----
 
An '''''integer literal''represents a fixed-point numeric value. An integer literal must begin with one of the numeric digits 0 - 9, and may be optionally terminated with a suffix character called a '''''radix specifier''. The radix specifier tells the assembler whether the literal is to be interpreted as a base 2 (binary), 8 (octal), 10 (decimal), or 16 ( hexadecimal) number. If the literal is not suffixed with a radix specifier , the assembler uses the value of the current radix to determine the base of the number. The default radix is 10 (decimal), but the '''''.RADIX''directive can be used to specify an alternate radix.'''''''''
 
 
-----
 
''Integer-Literal'''':'' <br />[[00205.htm|''Binary-Integer-Literal'']] <br />[[00210.htm|''Octal-Integer-Literal'']] <br />[[00215.htm|''Decimal-Integer-Literal'']] <br />[[00220.htm|''Hexadecimal-Integer-Literal'']] <br /> <br />
 
[[[00202.htm|prev]]][[[00204.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
An ''integer literal''represents a fixed-point numeric value. An integer literal must begin with one of the numeric digits 0 - 9, and may be optionally terminated with a suffix character called a ''radix specifier''. The radix specifier tells the assembler whether the literal is to be interpreted as a base 2 (binary), 8 (octal), 10 (decimal), or 16 ( hexadecimal) number. If the literal is not suffixed with a radix specifier , the assembler uses the value of the current radix to determine the base of the number. The default radix is 10 (decimal), but the ''.RADIX''directive can be used to specify an alternate radix.
 
[[[00203.htm|prev]]][[[00205.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Integer-Literal'''':'' <br />[[00205.htm|''Binary-Integer-Literal'']] <br />[[00210.htm|''Octal-Integer-Literal'']] <br />[[00215.htm|''Decimal-Integer-Literal'']] <br />[[00220.htm|''Hexadecimal-Integer-Literal'']] <br /> <br />
 
[[[00204.htm|prev]]][[[00206.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Binary Integer Literals ===
 
 
-----
 
[[00208.htm|Description]]
 
[[00209.htm|Examples]]
 
 
-----
 
A base-2 number containing either of the digits '''''0''and '''''1''.''''''
 
 
-----
 
''Binary-Integer-Literal'''':'' <br />''Unqualified-Binary-Integer-Literal'' <br />''Qualified-Binary-Integer-Literal'' <br /> <br />''Unqualified-Binary-Integer-Literal:'' <br />''Binary-Digit'' <br />''Binary-Integer-Literal''''Binary-Digit'' <br /> <br />''Qualified-Binary-Integer-Literal:'' <br />''Unqualified-Binary-Integer-Literal Binary-Radix'' <br /> <br />''Binary-Digit:'' <br />'''0''' <br />'''1''' <br /> <br />''Binary-Radix:'' <br />'''b''' <br />'''B''' <br />'''y''' <br />'''Y''' <br />
 
[[[00205.htm|prev]]][[[00207.htm|next]]][[[00205.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00208.htm|Description]]
 
[[00209.htm|Examples]]
 
[[[00206.htm|prev]]][[[00208.htm|next]]][[[00205.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Binary-Integer-Literal'''':'' <br />''Unqualified-Binary-Integer-Literal'' <br />''Qualified-Binary-Integer-Literal'' <br /> <br />''Unqualified-Binary-Integer-Literal:'' <br />''Binary-Digit'' <br />''Binary-Integer-Literal''''Binary-Digit'' <br /> <br />''Qualified-Binary-Integer-Literal:'' <br />''Unqualified-Binary-Integer-Literal Binary-Radix'' <br /> <br />''Binary-Digit:'' <br />'''0''' <br />'''1''' <br /> <br />''Binary-Radix:'' <br />'''b''' <br />'''B''' <br />'''y''' <br />'''Y''' <br />
 
[[[00207.htm|prev]]][[[00209.htm|next]]][[[00205.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A base-2 number containing either of the digits ''0''and ''1''.
 
[[[00208.htm|prev]]][[[00210.htm|next]]][[[00205.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following are examples of unqualified binary integer literals:
 
10101 <br />0 <br />000001 <br />1111000010101010 <br />
 
The following are examples of qualified binary integer literals:
 
00001111b <br />1111Y <br />00y <br />1111000010101010B <br />
 
[[[00209.htm|prev]]][[[00211.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Octal Integer Literals ===
 
 
-----
 
[[00213.htm|Description]]
 
[[00214.htm|Examples]]
 
 
-----
 
A base-8 number containing any of the digits '''''0''through '''''7''.''''''
 
 
-----
 
''Octal-Integer-Literal'''':'' <br />''Unqualified-Octal-Integer-Literal'' <br />''Qualified-Octal-Integer-Literal'' <br /> <br />''Unqualified-Octal-Integer-Literal:'' <br />''Octal-Digit'' <br />''Octal-Integer-Literal Octal-Digit'' <br /> <br />''Qualified-Octal-Integer-Literal:'' <br />''Unqualified-Octal-Integer-Literal Octal-Radix'' <br /> <br />''Octal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 <br />''' <br />''Octal-Radix:'' <br />'''o''' <br />'''O''' <br />'''q''' <br />'''Q''' <br />
 
[[[00210.htm|prev]]][[[00212.htm|next]]][[[00210.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00213.htm|Description]]
 
[[00214.htm|Examples]]
 
[[[00211.htm|prev]]][[[00213.htm|next]]][[[00210.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Octal-Integer-Literal'''':'' <br />''Unqualified-Octal-Integer-Literal'' <br />''Qualified-Octal-Integer-Literal'' <br /> <br />''Unqualified-Octal-Integer-Literal:'' <br />''Octal-Digit'' <br />''Octal-Integer-Literal Octal-Digit'' <br /> <br />''Qualified-Octal-Integer-Literal:'' <br />''Unqualified-Octal-Integer-Literal Octal-Radix'' <br /> <br />''Octal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 <br />''' <br />''Octal-Radix:'' <br />'''o''' <br />'''O''' <br />'''q''' <br />'''Q''' <br />
 
[[[00212.htm|prev]]][[[00214.htm|next]]][[[00210.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A base-8 number containing any of the digits ''0''through ''7''.
 
[[[00213.htm|prev]]][[[00215.htm|next]]][[[00210.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following are examples of unqualified octal integer literals:
 
01234567 <br />27 <br />765 <br />
 
The following are examples of qualified octal integer literals:
 
27q <br />013o <br />567O <br />01234567Q <br />
 
[[[00214.htm|prev]]][[[00216.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Decimal Integer Literals ===
 
 
-----
 
[[00218.htm|Description]]
 
[[00219.htm|Examples]]
 
 
-----
 
A base-10 number containing any of the digits '''''0''through '''''9''.''''''
 
 
-----
 
''Decimal-Integer-Literal'''':'' <br />''Unqualified-Decimal-Integer-Literal'' <br />''Qualified-Decimal-Integer-Literal'' <br /> <br />''Unqualified-Decimal-Integer-Literal:'' <br />''Decimal-Digit'' <br />''Decimal-Integer-Literal Decimal-Digit'' <br /> <br />''Qualified-Decimal-Integer-Literal:'' <br />''Unqualified-Decimal-Integer-Literal Decimal-Radix'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Decimal-Radix:'' <br />'''d''' <br />'''D''' <br />'''t''' <br />'''T''' <br />
 
[[[00215.htm|prev]]][[[00217.htm|next]]][[[00215.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00218.htm|Description]]
 
[[00219.htm|Examples]]
 
[[[00216.htm|prev]]][[[00218.htm|next]]][[[00215.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Decimal-Integer-Literal'''':'' <br />''Unqualified-Decimal-Integer-Literal'' <br />''Qualified-Decimal-Integer-Literal'' <br /> <br />''Unqualified-Decimal-Integer-Literal:'' <br />''Decimal-Digit'' <br />''Decimal-Integer-Literal Decimal-Digit'' <br /> <br />''Qualified-Decimal-Integer-Literal:'' <br />''Unqualified-Decimal-Integer-Literal Decimal-Radix'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Decimal-Radix:'' <br />'''d''' <br />'''D''' <br />'''t''' <br />'''T''' <br />
 
[[[00217.htm|prev]]][[[00219.htm|next]]][[[00215.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A base-10 number containing any of the digits ''0''through ''9''.
 
[[[00218.htm|prev]]][[[00220.htm|next]]][[[00215.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following are examples of unqualified decimal integer literals:
 
0123456789 <br />19 <br />090 <br />
 
The following are examples of qualified decimal integer literals:
 
01d <br />89t <br />4567D <br />0123456789T <br />
 
[[[00219.htm|prev]]][[[00221.htm|next]]][[[00202.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Hexadecimal Integer Literals ===
 
 
-----
 
[[00223.htm|Description]]
 
[[00224.htm|Constraints]]
 
[[00225.htm|Examples]]
 
 
-----
 
A base-16 number using any combination of the digits '''0'''through '''9'''and the lowercase letters '''a'''through '''f'''or the uppercase letters '''A'''through '''F'''. The lowercase and uppercase representations of any given hexadecimal letter are equivalent.
 
 
-----
 
''Hexadecimal-Integer-Literal'''':'' <br />''Unqualified-Hexadecimal-Integer-Literal'' <br />''Qualified-Hexadecimal-Integer-Literal'' <br /> <br />''Unqualified-Hexadecimal-Integer-Literal:'' <br />''Decimal-Digit'' <br />''Hexadecimal-Integer-Literal Decimal-Digit'' <br />''Hexadecimal-Integer-Literal Hexadecimal-Digit'' <br /> <br />''Qualified-Hexadecimal-Integer-Literal:'' <br />''Unqualified-Hexadecimal-Integer-Literal Hexadecimal-Radix'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Hexadecimal-Digit:'' one of: '''<br />a b c d e f <br />A B C D E F <br />''' <br />''Hexadecimal-Radix:'' <br />'''h''' <br />'''H''' <br />
 
[[[00220.htm|prev]]][[[00222.htm|next]]][[[00220.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00223.htm|Description]]
 
[[00224.htm|Constraints]]
 
[[00225.htm|Examples]]
 
[[[00221.htm|prev]]][[[00223.htm|next]]][[[00220.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Hexadecimal-Integer-Literal'''':'' <br />''Unqualified-Hexadecimal-Integer-Literal'' <br />''Qualified-Hexadecimal-Integer-Literal'' <br /> <br />''Unqualified-Hexadecimal-Integer-Literal:'' <br />''Decimal-Digit'' <br />''Hexadecimal-Integer-Literal Decimal-Digit'' <br />''Hexadecimal-Integer-Literal Hexadecimal-Digit'' <br /> <br />''Qualified-Hexadecimal-Integer-Literal:'' <br />''Unqualified-Hexadecimal-Integer-Literal Hexadecimal-Radix'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Hexadecimal-Digit:'' one of: '''<br />a b c d e f <br />A B C D E F <br />''' <br />''Hexadecimal-Radix:'' <br />'''h''' <br />'''H''' <br />
 
[[[00222.htm|prev]]][[[00224.htm|next]]][[[00220.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A base-16 number using any combination of the digits '''0'''through '''9'''and the lowercase letters '''a'''through '''f'''or the uppercase letters '''A'''through '''F'''. The lowercase and uppercase representations of any given hexadecimal letter are equivalent.
 
[[[00223.htm|prev]]][[[00225.htm|next]]][[[00220.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
A hexadecimal integer literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the ''0''digit.
 
[[[00224.htm|prev]]][[[00226.htm|next]]][[[00220.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following are examples of unqualified hexadecimal integer literals:
 
01BD <br />9A <br />0AB <br />
 
The following are examples of qualified hexadecimal integer literals:
 
1234ABCDh <br />01DH <br />0bh <br />1111FFFFH <br />
 
[[[00225.htm|prev]]][[[00227.htm|next]]][[[00199.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Floating-Point Literals ===
 
 
-----
 
A '''''floating-point literal''is a notation for representing real numbers. The assembler provides both decimal and hexadecimal floating-point notations for representing real numbers.'''
 
 
-----
 
''Floating-Point-Literal'''':'' <br />[[00229.htm|''Decimal-Floating-Point-Literal'']] <br />[[00235.htm|''Hexadecimal-Floating-Point-Literal'']] <br /> <br />
 
[[[00226.htm|prev]]][[[00228.htm|next]]][[[00226.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''floating-point literal''is a notation for representing real numbers. The assembler provides both decimal and hexadecimal floating-point notations for representing real numbers.
 
[[[00227.htm|prev]]][[[00229.htm|next]]][[[00226.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Floating-Point-Literal'''':'' <br />[[00229.htm|''Decimal-Floating-Point-Literal'']] <br />[[00235.htm|''Hexadecimal-Floating-Point-Literal'']] <br /> <br />
 
[[[00228.htm|prev]]][[[00230.htm|next]]][[[00226.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Decimal Floating-Point Literals ===
 
 
-----
 
[[00232.htm|Description]]
 
[[00233.htm|Constraints]]
 
[[00234.htm|Examples]]
 
 
-----
 
A decimal floating-point literal has a ''significand part''that may be followed by an ''exponent part''. The significand part consists of a digit sequence representing the whole-number part, followed by a period (.), followed by a digit sequence representing the fraction part. The exponent part consists of an introductory character ('''e'''or '''E'''), followed by an optional sign character ('''+'''or '''-'''), followed by a digit sequence representing the exponent.
 
 
-----
 
''Decimal-Floating-Point-Literal'''':'' <br />''Significand-Part'' <br />''Significand-Part Exponent-Part'' <br /> <br />''Significand-Part:'' <br />''Digit-Sequence'''''.'''''Digit-Sequence'' <br />''Digit-Sequence'''''.''' <br /> <br />''Exponent-Part:'' <br />''E-Character Digit-Sequence'' <br />''E-Character Sign Digit-Sequence'' <br /> <br />''E-Character:'' <br />'''e''' <br />'''E''' <br /> <br />''Sign:'' <br />'''-''' <br />'''+''' <br /> <br />''Digit-Sequence:'' <br />''Digit'' <br />''Digit-Sequence Digit'' <br /> <br />''Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />
 
[[[00229.htm|prev]]][[[00231.htm|next]]][[[00229.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00232.htm|Description]]
 
[[00233.htm|Constraints]]
 
[[00234.htm|Examples]]
 
[[[00230.htm|prev]]][[[00232.htm|next]]][[[00229.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Decimal-Floating-Point-Literal'''':'' <br />''Significand-Part'' <br />''Significand-Part Exponent-Part'' <br /> <br />''Significand-Part:'' <br />''Digit-Sequence'''''.'''''Digit-Sequence'' <br />''Digit-Sequence'''''.''' <br /> <br />''Exponent-Part:'' <br />''E-Character Digit-Sequence'' <br />''E-Character Sign Digit-Sequence'' <br /> <br />''E-Character:'' <br />'''e''' <br />'''E''' <br /> <br />''Sign:'' <br />'''-''' <br />'''+''' <br /> <br />''Digit-Sequence:'' <br />''Digit'' <br />''Digit-Sequence Digit'' <br /> <br />''Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />
 
[[[00231.htm|prev]]][[[00233.htm|next]]][[[00229.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A decimal floating-point literal has a ''significand part''that may be followed by an ''exponent part''. The significand part consists of a digit sequence representing the whole-number part, followed by a period (.), followed by a digit sequence representing the fraction part. The exponent part consists of an introductory character ('''e'''or '''E'''), followed by an optional sign character ('''+'''or '''-'''), followed by a digit sequence representing the exponent.
 
[[[00232.htm|prev]]][[[00234.htm|next]]][[[00229.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The introductory ''Digit-Sequence''in the ''Significand-Part''must be specified ( the literal cannot begin with a &quot;.&quot;).
 
[[[00233.htm|prev]]][[[00235.htm|next]]][[[00229.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  25 . 23
  2 . 523E1
  2523 . 0E - 2 </pre>
[[[00234.htm|prev]]][[[00236.htm|next]]][[[00226.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Hexadecimal Floating-Point Literals ===
 
 
-----
 
[[00238.htm|Description]]
 
[[00239.htm|Constraints]]
 
[[00240.htm|Examples]]
 
 
-----
 
A hexadecimal floating-point literal provides a means of initializing floating point values using a notation more closely tied to the internal machine representation than that of the [[00229.htm|''Decimal-Floating-Point-Literal'']]. Such literals are coded in a fashion similar to that of a normal [[00220.htm|''Hexadecimal-Integer-Literal'']], but a different radix suffix is used to inform the assembler that the value is to be used in the allocation of real numbers rather than integers.
 
 
 
 
-----
 
''Hexadecimal-Floating-Point-Literal'''':'' <br />''Hexadecimal-Literal Float-Radix'' <br /> <br />''Hexadecimal-Literal:'' <br />''Decimal-Digit'' <br />''Hexadecimal-Literal Decimal-Digit'' <br />''Hexadecimal-Literal Hexadecimal-Digit'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Hexadecimal-Digit:'' one of: '''<br />a b c d e f <br />A B C D E F <br />''' <br />''Float-Radix:'' <br />'''r''' <br />'''R''' <br />
 
[[[00235.htm|prev]]][[[00237.htm|next]]][[[00235.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00238.htm|Description]]
 
[[00239.htm|Constraints]]
 
[[00240.htm|Examples]]
 
[[[00236.htm|prev]]][[[00238.htm|next]]][[[00235.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Hexadecimal-Floating-Point-Literal'''':'' <br />''Hexadecimal-Literal Float-Radix'' <br /> <br />''Hexadecimal-Literal:'' <br />''Decimal-Digit'' <br />''Hexadecimal-Literal Decimal-Digit'' <br />''Hexadecimal-Literal Hexadecimal-Digit'' <br /> <br />''Decimal-Digit:'' one of: '''<br />0 1 2 3 4 5 6 7 8 9 <br />''' <br />''Hexadecimal-Digit:'' one of: '''<br />a b c d e f <br />A B C D E F <br />''' <br />''Float-Radix:'' <br />'''r''' <br />'''R''' <br />
 
[[[00237.htm|prev]]][[[00239.htm|next]]][[[00235.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A hexadecimal floating-point literal provides a means of initializing floating point values using a notation more closely tied to the internal machine representation than that of the [[00229.htm|''Decimal-Floating-Point-Literal'']]. Such literals are coded in a fashion similar to that of a normal [[00220.htm|''Hexadecimal-Integer-Literal'']], but a different radix suffix is used to inform the assembler that the value is to be used in the allocation of real numbers rather than integers.
 
[[[00238.htm|prev]]][[[00240.htm|next]]][[[00235.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
A hexadecimal floating-point literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the '''''0''digit.'''
 
The literal must specify the correct number of hexadecimal digits according to the size of the real-number data-type to which it will be assigned. For '''REAL4''', '''REAL8''', and '''REAL10'''variables, the respective number of digits in the literal must be 8, 16, and 20. For literals encoded with a leading zero, the respective number of digits must be 9, 17, and 21.
 
[[[00239.htm|prev]]][[[00241.htm|next]]][[[00235.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>3F800000r </pre>
[[[00240.htm|prev]]][[[00242.htm|next]]][[[00199.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== String Literals ===
 
 
-----
 
[[00244.htm|Description]]
 
[[00245.htm|Examples]]
 
 
-----
 
A '''''string literal''contains a sequence of zero or more characters enclosed in quotation mark symbols. Either a single (') or double (&quot;) quotation mark symbol may be used as the '''''quote character''that opens and closes the string literal. If a single quotation mark symbol is used as the quote character, then double quotation mark symbols may appear as data characters within the string literal, and vice versa. If the quote character must also appear as a character within the string literal, use two adjacent quote characters; this will allow a single occurrence of the quote character to be inserted into the string literal.''''''
 
A quote character must be used to terminate the string literal before the end of the line is reached, otherwise an error message is issued and the literal is terminated by the end of line character. A string literal may span multiple lines only if a backslash (\) appears as the last non- whitespace character on the line, in which case the backslash, all surrounding whitespace characters, and the end of line character are deleted and the literal is continued with the first character on the next line.
 
 
-----
 
''String-Literal'''':'' <br />''D-String'' <br />''S-String'' <br /> <br />''D-String'''':'' <br />''D-Quote D-Quote'' <br />''D-Quote D-Char-Sequence D-Quote'' <br /> <br />''S-String'''':'' <br />''S-Quote S-Quote'' <br />''S-Quote S-Char-Sequence S-Quote'' <br /> <br />''D-Char-Sequence'''':'' <br />any printable character except ''D-Quote'' <br />''D-Quote D-Quote'' <br /> <br />''S-Char-Sequence'''':'' <br />any printable character except ''S-Quote'' <br />''S-Quote S-Quote'' <br /> <br />''D-Quote'''':'' <br />'''&quot;''' <br /> <br />''S-Quote'''':'' <br />''''''' <br /> <br />
 
[[[00241.htm|prev]]][[[00243.htm|next]]][[[00241.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00244.htm|Description]]
 
[[00245.htm|Examples]]
 
[[[00242.htm|prev]]][[[00244.htm|next]]][[[00241.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''String-Literal'''':'' <br />''D-String'' <br />''S-String'' <br /> <br />''D-String'''':'' <br />''D-Quote D-Quote'' <br />''D-Quote D-Char-Sequence D-Quote'' <br /> <br />''S-String'''':'' <br />''S-Quote S-Quote'' <br />''S-Quote S-Char-Sequence S-Quote'' <br /> <br />''D-Char-Sequence'''':'' <br />any printable character except ''D-Quote'' <br />''D-Quote D-Quote'' <br /> <br />''S-Char-Sequence'''':'' <br />any printable character except ''S-Quote'' <br />''S-Quote S-Quote'' <br /> <br />''D-Quote'''':'' <br />'''&quot;''' <br /> <br />''S-Quote'''':'' <br />''''''' <br /> <br />
 
[[[00243.htm|prev]]][[[00245.htm|next]]][[[00241.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A '''''string literal''contains a sequence of zero or more characters enclosed in quotation mark symbols. Either a single (') or double (&quot;) quotation mark symbol may be used as the '''''quote character''that opens and closes the string literal. If a single quotation mark symbol is used as the quote character, then double quotation mark symbols may appear as data characters within the string literal, and vice versa. If the quote character must also appear as a character within the string literal, use two adjacent quote characters; this will allow a single occurrence of the quote character to be inserted into the string literal.''''''
 
A quote character must be used to terminate the string literal before the end of the line is reached, otherwise an error message is issued and the literal is terminated by the end of line character. A string literal may span multiple lines only if a backslash (\) appears as the last non- whitespace character on the line, in which case the backslash, all surrounding whitespace characters, and the end of line character are deleted and the literal is continued with the first character on the next line.
 
[[[00244.htm|prev]]][[[00246.htm|next]]][[[00241.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>'Hello, world'
&quot;That's the way it is&quot;
'Unless it''s not'
&quot;SuperStringCon \
catenated&quot;</pre>
[[[00245.htm|prev]]][[[00247.htm|next]]][[[00107.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Punctuators ===
 
 
-----
 
Punctuators are used as operators and separator characters.
 
 
-----
 
''Punctuator'''':'' one of '''<br />[ ] ( ) { } * , : = ; %''' <br /> <br />
 
[[[00246.htm|prev]]][[[00248.htm|next]]][[[00246.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Punctuators are used as operators and separator characters.
 
[[[00247.htm|prev]]][[[00249.htm|next]]][[[00246.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Punctuator'''':'' one of '''<br />[ ] ( ) { } * , : = ; %''' <br /> <br />
 
[[[00248.htm|prev]]][[[00250.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Declarations ===
 
A ''Type Declaration''is a language construct that specifies the characteristics of code and data objects used in a program.
 
[[[00249.htm|prev]]][[[00251.htm|next]]][[[00249.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Declarations ===
 
 
-----
 
A ''Type-Declaration''is a common construct used in various assembler directives to establish type attribute information for a program object. A ''Type-Declaration''is needed to determine the data type of a variable or labeled address. The [[00783.htm|TYPEDEF]]directive offers a method of assigning a name to a ''Type-Declaration''.
 
 
-----
 
''Type-Declaration'''':'' <br />''TypeName'' <br />''TypeName''''Array-Spec'' <br />''Pointer-Spec'' <br />''Pointer-Spec''''TypeName'' <br />''Pointer-Spec''''TypeName''''Array-Spec'' <br /> <br />''Pointer-Spec'''':'' <br />'''PTR''' <br />[[00128.htm|''Distance-TypeName'']]'''PTR''' <br />''Pointer-Spec''''Array-Spec'' <br /> <br />''Array-Spec'''':'' <br />'''['''[[00255.htm|''Expression'']]''']''' <br />''Array-Spec'''''['''[[00255.htm|''Expression'']]''']''' <br /> <br />''TypeName'''':'' <br />[[00128.htm|''Distance-TypeName'']] <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00171.htm|''UserDefined-TypeName'']] <br /> <br />
 
 
-----
 
The '''TYPEDEF'''directive is used to illustrate the type declaration syntax: <br />
 
<pre>CHAR        typedef  byte              ;  Alias  of  intrinsic  TypeName
PBYTE      typedef  ptr  byte          ;  Pointer  to  intrinsic  TypeName
PCHAR      typedef  ptr  CHAR          ;  Pointer  to  TypeDef - TypeName
PPCHAR      typedef  ptr  PCHAR        ;  Pointer  to  a  pointer  to  a  CHAR
PPBYTE      typedef  ptr  ptr  byte      ;  Similar  to  PPCHAR
PVOID      typedef  ptr                ;  Pointer  to  nothing  ( pointer  to  code )
PCODE      typedef  ptr  PROC          ;  Similar  to  PVOID
PFCODE      typedef  far  ptr  far      ;  Far  pointer  to  far  code  address
 
;  vector  declarations
 
ACHAR      typedef  CHAR [ 16 ]          ;  Array  of  16  characters
AAWORD      typedef  word [ 2 ] [ 2 ]        ;  multi - dimensional  array
APBYTE      typedef  ptr [ 8 ]  byte      ;  Array  of  8  pointers  to  byte
APACHAR    typedef  ptr [ 4 ]  ACHAR      ;  Array  of  4  ptrs  to  arrays  of  16  chars
 
SIZES _ T    struct                    ;  define  an  intrinsic  structure  type
  little    byte      ?
  Medium    word      ?
  BIG      dword    ?
SIZES _ T    ends
 
SIZES      typedef  SIZES _ T          ;  alias  for  intrinsic  structure  type
PSIZES      typedef  ptr  SIZES _ T      ;  and  a  type  to  point  to  it
 
PFORWARD    typedef  ptr  FORWARD      ;  Pointers  to  forward - referenced  types
FORWARD    struct                    ;  are  assumed  to  be  pointers  to  structs
  blah      word      ?
FORWARD    ends </pre>
[[[00250.htm|prev]]][[[00252.htm|next]]][[[00250.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Type-Declaration''is a common construct used in various assembler directives to establish type attribute information for a program object. A ''Type-Declaration''is needed to determine the data type of a variable or labeled address. The [[00783.htm|TYPEDEF]]directive offers a method of assigning a name to a ''Type-Declaration''.
 
[[[00251.htm|prev]]][[[00253.htm|next]]][[[00250.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Type-Declaration'''':'' <br />''TypeName'' <br />''TypeName''''Array-Spec'' <br />''Pointer-Spec'' <br />''Pointer-Spec''''TypeName'' <br />''Pointer-Spec''''TypeName''''Array-Spec'' <br /> <br />''Pointer-Spec'''':'' <br />'''PTR''' <br />[[00128.htm|''Distance-TypeName'']]'''PTR''' <br />''Pointer-Spec''''Array-Spec'' <br /> <br />''Array-Spec'''':'' <br />'''['''[[00255.htm|''Expression'']]''']''' <br />''Array-Spec'''''['''[[00255.htm|''Expression'']]''']''' <br /> <br />''TypeName'''':'' <br />[[00128.htm|''Distance-TypeName'']] <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00171.htm|''UserDefined-TypeName'']] <br /> <br />
 
[[[00252.htm|prev]]][[[00254.htm|next]]][[[00250.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The '''TYPEDEF'''directive is used to illustrate the type declaration syntax: <br />
 
<pre>CHAR        typedef  byte              ;  Alias  of  intrinsic  TypeName
PBYTE      typedef  ptr  byte          ;  Pointer  to  intrinsic  TypeName
PCHAR      typedef  ptr  CHAR          ;  Pointer  to  TypeDef - TypeName
PPCHAR      typedef  ptr  PCHAR        ;  Pointer  to  a  pointer  to  a  CHAR
PPBYTE      typedef  ptr  ptr  byte      ;  Similar  to  PPCHAR
PVOID      typedef  ptr                ;  Pointer  to  nothing  ( pointer  to  code )
PCODE      typedef  ptr  PROC          ;  Similar  to  PVOID
PFCODE      typedef  far  ptr  far      ;  Far  pointer  to  far  code  address
 
;  vector  declarations
 
ACHAR      typedef  CHAR [ 16 ]          ;  Array  of  16  characters
AAWORD      typedef  word [ 2 ] [ 2 ]        ;  multi - dimensional  array
APBYTE      typedef  ptr [ 8 ]  byte      ;  Array  of  8  pointers  to  byte
APACHAR    typedef  ptr [ 4 ]  ACHAR      ;  Array  of  4  ptrs  to  arrays  of  16  chars
 
SIZES _ T    struct                    ;  define  an  intrinsic  structure  type
  little    byte      ?
  Medium    word      ?
  BIG      dword    ?
SIZES _ T    ends
 
SIZES      typedef  SIZES _ T          ;  alias  for  intrinsic  structure  type
PSIZES      typedef  ptr  SIZES _ T      ;  and  a  type  to  point  to  it
 
PFORWARD    typedef  ptr  FORWARD      ;  Pointers  to  forward - referenced  types
FORWARD    struct                    ;  are  assumed  to  be  pointers  to  structs
  blah      word      ?
FORWARD    ends </pre>
[[[00253.htm|prev]]][[[00255.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Expressions ===
 
An expression is a sequence of ''operators''and ''operands''that are evaluated to derive a numeric result, an effective address, or a register operand.
 
Expressions are specified using standard infix notation, which is recursive in nature, ie., expressions may be nested within other expressions. The evaluation of an expression occurs in a left to right manner, and is influenced by the rules of operator ''precedence''and ''associativity''. The order in which expressions are evaluated can be controlled by grouping operands and operators together using parentheses ().
 
[[[00254.htm|prev]]][[[00256.htm|next]]][[[00254.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Expression Syntax ===
 
 
-----
 
This section describes the complete expression syntax.
 
 
-----
 
''Expression'''':'' <br />[[00258.htm|''Duplicative-Expression'']] <br /> <br />[[00258.htm|''Duplicative-Expression'']]'':'' <br />[[00267.htm|''Attribute-Expression'']] <br />[[00267.htm|''Attribute-Expression'']][[00261.htm|DUP]]'''('''''Initializer-List''''')''' <br /> <br />[[00267.htm|''Attribute-Expression'']]'':'' <br />[[00287.htm|''OR-Expression'']] <br />[[00281.htm|SHORT]][[00359.htm|''Additive-Expression'']] <br />[[00270.htm|.TYPE]][[00287.htm|''OR-Expression'']] <br />[[00275.htm|OPATTR]][[00287.htm|''OR-Expression'']] <br /> <br />[[00287.htm|''OR-Expression'']]'':'' <br />[[00302.htm|''AND-Expression'']] <br />[[00287.htm|''OR-Expression'']][[00290.htm|OR]][[00302.htm|''AND-Expression'']] <br />[[00287.htm|''OR-Expression'']][[00296.htm|XOR]][[00302.htm|''AND-Expression'']] <br /> <br />[[00302.htm|''AND-Expression'']]'':'' <br />[[00311.htm|''NOT-Expression'']] <br />[[00302.htm|''AND-Expression'']][[00305.htm|AND]][[00311.htm|''NOT-Expression'']] <br /> <br />[[00311.htm|''NOT-Expression'']]'':'' <br />[[00320.htm|''Relational-Expression'']] <br />[[00314.htm|NOT]][[00320.htm|''Relational-Expression'']] <br /> <br />[[00320.htm|''Relational-Expression'']]'':'' <br />[[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00323.htm|EQ]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00329.htm|NE]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00335.htm|GT]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00341.htm|GE]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00347.htm|LT]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00353.htm|LE]][[00359.htm|''Additive-Expression'']] <br /> <br />[[00359.htm|''Additive-Expression'']]'':'' <br />[[00374.htm|''Multiplicative-Expression'']] <br />[[00359.htm|''Additive-Expression'']][[00362.htm|+]][[00374.htm|''Multiplicative-Expression'']] <br />[[00359.htm|''Additive-Expression'']][[00368.htm|-]][[00374.htm|''Multiplicative-Expression'']] <br /> <br />[[00374.htm|''Multiplicative-Expression'']]'':'' <br />[[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00377.htm|*]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00383.htm|/]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00389.htm|MOD]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00395.htm|SHL]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00401.htm|SHR]][[00407.htm|''Narrowed-Expression'']] <br /> <br />[[00407.htm|''Narrowed-Expression'']]'':'' <br />[[00434.htm|''Cast-Expression'']] <br />[[00410.htm|HIGH]][[00434.htm|''Cast-Expression'']] <br />[[00416.htm|HIGHWORD]][[00434.htm|''Cast-Expression'']] <br />[[00422.htm|LOW]][[00434.htm|''Cast-Expression'']] <br />[[00428.htm|LOWWORD]][[00434.htm|''Cast-Expression'']] <br /> <br />[[00434.htm|''Cast-Expression'']]'':'' <br />[[00473.htm|''Element-Selection-Expression'']] <br />[[00437.htm|OFFSET]][[00434.htm|''Cast-Expression'']] <br />[[00443.htm|SEG]][[00434.htm|''Cast-Expression'']] <br />[[00449.htm|THIS]][[00473.htm|''Element-Selection-Expression'']] <br />[[00455.htm|TYPE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00434.htm|''Cast-Expression'']][[00461.htm|PTR]][[00434.htm|''Cast-Expression'']] <br />[[00434.htm|''Cast-Expression'']][[00467.htm|:]][[00434.htm|''Cast-Expression'']] <br /> <br />[[00473.htm|''Element-Selection-Expression'']]'':'' <br />[[00488.htm|''Sign-Expression'']] <br />[[00473.htm|''Element-Selection-Expression'']][[00476.htm|[]][[00488.htm|''Sign-Expression'']][[00476.htm|00476.htm]]] <br />[[00473.htm|''Element-Selection-Expression'']][[00482.htm|.]][[00488.htm|''Sign-Expression'']] <br /> <br />[[00488.htm|''Sign-Expression'']]'':'' <br />[[00503.htm|''Primary-Expression'']] <br />[[00491.htm|-]][[00503.htm|''Primary-Expression'']] <br />[[00497.htm|+]][[00503.htm|''Primary-Expression'']] <br /> <br />[[00503.htm|''Primary-Expression'']]'':'' <br />[[00506.htm|''Literal-Operand'']] <br />[[00516.htm|''Record-Constant'']] <br />[[00527.htm|''Identifier-Operand'']] <br />[[00522.htm|''Register-Operand'']] <br />[[00532.htm|''Integral-TypeName-Operand'']] <br />[[00511.htm|''Value-Substitution-Operand'']] <br />[[00537.htm|LENGTH]][[00527.htm|''Identifier-Operand'']] <br />[[00542.htm|LENGTHOF]][[00527.htm|''Identifier-Operand'']] <br />[[00548.htm|MASK]][[00527.htm|''Identifier-Operand'']] <br />[[00553.htm|SIZE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00558.htm|SIZEOF]][[00473.htm|''Element-Selection-Expression'']] <br />[[00563.htm|WIDTH]][[00527.htm|''Identifier-Operand'']] <br />[[00568.htm|''Parenthesized-Expression'']] <br />[[00573.htm|''Indirected-Expression'']] <br />[[00579.htm|''Compound-Initializer'']] <br /> <br />[[00506.htm|''Literal-Operand'']]'':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />[[00516.htm|''Record-Constant'']]'':'' <br />[[00527.htm|''Identifier-Operand'']]'''&lt;'''''Field-List'''''&gt;''' <br />[[00527.htm|''Identifier-Operand'']]'''{'''''Field-List'''''}''' <br /> <br />''Field-List:'' <br />[[00267.htm|''Attribute-Expression'']] <br />''Field-List''''','''[[00267.htm|''Attribute-Expression'']] <br /> <br />[[00527.htm|''Identifier-Operand'']]'':'' <br />[[00149.htm|''Identifier'']] <br /> <br />[[00522.htm|''Register-Operand'']]'':'' <br />[[00122.htm|''Processor-Register'']] <br /> <br />[[00532.htm|''Integral-TypeName-Operand'']]'':'' <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br /> <br />[[00511.htm|''Value-Substitution-Operand'']]'':'' <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />'''FLAT''' <br /> <br />[[00568.htm|''Parenthesized-Expression'']]'':'' <br />'''('''[[00267.htm|''Attribute-Expression'']]''')''' <br /> <br />[[00573.htm|''Indirected-Expression'']]'':'' <br />'''['''[[00267.htm|''Attribute-Expression'']]''']''' <br /> <br />[[00579.htm|''Compound-Initializer'']]'':'' <br />'''&lt;'''''Initializer-List'''''&gt;''' <br />'''{'''''Initializer-List'''''}''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
[[[00255.htm|prev]]][[[00257.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
This section describes the complete expression syntax.
 
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=== Syntax ===
 
''Expression'''':'' <br />[[00258.htm|''Duplicative-Expression'']] <br /> <br />[[00258.htm|''Duplicative-Expression'']]'':'' <br />[[00267.htm|''Attribute-Expression'']] <br />[[00267.htm|''Attribute-Expression'']][[00261.htm|DUP]]'''('''''Initializer-List''''')''' <br /> <br />[[00267.htm|''Attribute-Expression'']]'':'' <br />[[00287.htm|''OR-Expression'']] <br />[[00281.htm|SHORT]][[00359.htm|''Additive-Expression'']] <br />[[00270.htm|.TYPE]][[00287.htm|''OR-Expression'']] <br />[[00275.htm|OPATTR]][[00287.htm|''OR-Expression'']] <br /> <br />[[00287.htm|''OR-Expression'']]'':'' <br />[[00302.htm|''AND-Expression'']] <br />[[00287.htm|''OR-Expression'']][[00290.htm|OR]][[00302.htm|''AND-Expression'']] <br />[[00287.htm|''OR-Expression'']][[00296.htm|XOR]][[00302.htm|''AND-Expression'']] <br /> <br />[[00302.htm|''AND-Expression'']]'':'' <br />[[00311.htm|''NOT-Expression'']] <br />[[00302.htm|''AND-Expression'']][[00305.htm|AND]][[00311.htm|''NOT-Expression'']] <br /> <br />[[00311.htm|''NOT-Expression'']]'':'' <br />[[00320.htm|''Relational-Expression'']] <br />[[00314.htm|NOT]][[00320.htm|''Relational-Expression'']] <br /> <br />[[00320.htm|''Relational-Expression'']]'':'' <br />[[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00323.htm|EQ]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00329.htm|NE]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00335.htm|GT]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00341.htm|GE]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00347.htm|LT]][[00359.htm|''Additive-Expression'']] <br />[[00320.htm|''Relational-Expression'']][[00353.htm|LE]][[00359.htm|''Additive-Expression'']] <br /> <br />[[00359.htm|''Additive-Expression'']]'':'' <br />[[00374.htm|''Multiplicative-Expression'']] <br />[[00359.htm|''Additive-Expression'']][[00362.htm|+]][[00374.htm|''Multiplicative-Expression'']] <br />[[00359.htm|''Additive-Expression'']][[00368.htm|-]][[00374.htm|''Multiplicative-Expression'']] <br /> <br />[[00374.htm|''Multiplicative-Expression'']]'':'' <br />[[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00377.htm|*]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00383.htm|/]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00389.htm|MOD]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00395.htm|SHL]][[00407.htm|''Narrowed-Expression'']] <br />[[00374.htm|''Multiplicative-Expression'']][[00401.htm|SHR]][[00407.htm|''Narrowed-Expression'']] <br /> <br />[[00407.htm|''Narrowed-Expression'']]'':'' <br />[[00434.htm|''Cast-Expression'']] <br />[[00410.htm|HIGH]][[00434.htm|''Cast-Expression'']] <br />[[00416.htm|HIGHWORD]][[00434.htm|''Cast-Expression'']] <br />[[00422.htm|LOW]][[00434.htm|''Cast-Expression'']] <br />[[00428.htm|LOWWORD]][[00434.htm|''Cast-Expression'']] <br /> <br />[[00434.htm|''Cast-Expression'']]'':'' <br />[[00473.htm|''Element-Selection-Expression'']] <br />[[00437.htm|OFFSET]][[00434.htm|''Cast-Expression'']] <br />[[00443.htm|SEG]][[00434.htm|''Cast-Expression'']] <br />[[00449.htm|THIS]][[00473.htm|''Element-Selection-Expression'']] <br />[[00455.htm|TYPE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00434.htm|''Cast-Expression'']][[00461.htm|PTR]][[00434.htm|''Cast-Expression'']] <br />[[00434.htm|''Cast-Expression'']][[00467.htm|:]][[00434.htm|''Cast-Expression'']] <br /> <br />[[00473.htm|''Element-Selection-Expression'']]'':'' <br />[[00488.htm|''Sign-Expression'']] <br />[[00473.htm|''Element-Selection-Expression'']][[00476.htm|[]][[00488.htm|''Sign-Expression'']][[00476.htm|00476.htm]]] <br />[[00473.htm|''Element-Selection-Expression'']][[00482.htm|.]][[00488.htm|''Sign-Expression'']] <br /> <br />[[00488.htm|''Sign-Expression'']]'':'' <br />[[00503.htm|''Primary-Expression'']] <br />[[00491.htm|-]][[00503.htm|''Primary-Expression'']] <br />[[00497.htm|+]][[00503.htm|''Primary-Expression'']] <br /> <br />[[00503.htm|''Primary-Expression'']]'':'' <br />[[00506.htm|''Literal-Operand'']] <br />[[00516.htm|''Record-Constant'']] <br />[[00527.htm|''Identifier-Operand'']] <br />[[00522.htm|''Register-Operand'']] <br />[[00532.htm|''Integral-TypeName-Operand'']] <br />[[00511.htm|''Value-Substitution-Operand'']] <br />[[00537.htm|LENGTH]][[00527.htm|''Identifier-Operand'']] <br />[[00542.htm|LENGTHOF]][[00527.htm|''Identifier-Operand'']] <br />[[00548.htm|MASK]][[00527.htm|''Identifier-Operand'']] <br />[[00553.htm|SIZE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00558.htm|SIZEOF]][[00473.htm|''Element-Selection-Expression'']] <br />[[00563.htm|WIDTH]][[00527.htm|''Identifier-Operand'']] <br />[[00568.htm|''Parenthesized-Expression'']] <br />[[00573.htm|''Indirected-Expression'']] <br />[[00579.htm|''Compound-Initializer'']] <br /> <br />[[00506.htm|''Literal-Operand'']]'':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />[[00516.htm|''Record-Constant'']]'':'' <br />[[00527.htm|''Identifier-Operand'']]'''&lt;'''''Field-List'''''&gt;''' <br />[[00527.htm|''Identifier-Operand'']]'''{'''''Field-List'''''}''' <br /> <br />''Field-List:'' <br />[[00267.htm|''Attribute-Expression'']] <br />''Field-List''''','''[[00267.htm|''Attribute-Expression'']] <br /> <br />[[00527.htm|''Identifier-Operand'']]'':'' <br />[[00149.htm|''Identifier'']] <br /> <br />[[00522.htm|''Register-Operand'']]'':'' <br />[[00122.htm|''Processor-Register'']] <br /> <br />[[00532.htm|''Integral-TypeName-Operand'']]'':'' <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br /> <br />[[00511.htm|''Value-Substitution-Operand'']]'':'' <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />'''FLAT''' <br /> <br />[[00568.htm|''Parenthesized-Expression'']]'':'' <br />'''('''[[00267.htm|''Attribute-Expression'']]''')''' <br /> <br />[[00573.htm|''Indirected-Expression'']]'':'' <br />'''['''[[00267.htm|''Attribute-Expression'']]''']''' <br /> <br />[[00579.htm|''Compound-Initializer'']]'':'' <br />'''&lt;'''''Initializer-List'''''&gt;''' <br />'''{'''''Initializer-List'''''}''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
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=== Duplicative Initialization Expression ===
 
 
-----
 
A '''''Duplicative Initialization Expression''is one that can be optionally used during the initialization of variables such that the operand is duplicated a specified number of times.'''
 
 
-----
 
''Duplicative-Expression'''':'' <br />[[00267.htm|''Attribute-Expression'']] <br />[[00267.htm|''Attribute-Expression'']][[00261.htm|DUP]]'''('''''Initializer-List''''')''' <br /> <br />''Initializer-List:'' <br />''Duplicative-Expression'' <br />''Initializer-List''''','''''Duplicative-Expression'' <br /> <br />
 
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=== Description ===
 
A ''Duplicative Initialization Expression''is one that can be optionally used during the initialization of variables such that the operand is duplicated a specified number of times.
 
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=== Syntax ===
 
''Duplicative-Expression'''':'' <br />[[00267.htm|''Attribute-Expression'']] <br />[[00267.htm|''Attribute-Expression'']][[00261.htm|DUP]]'''('''''Initializer-List''''')''' <br /> <br />''Initializer-List:'' <br />''Duplicative-Expression'' <br />''Initializer-List''''','''''Duplicative-Expression'' <br /> <br />
 
[[[00260.htm|prev]]][[[00262.htm|next]]][[[00258.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Duplicative Initialization (DUP Operator) ===
 
 
-----
 
[[00264.htm|Description]]
 
[[00265.htm|Constraints]]
 
[[00266.htm|Examples]]
 
 
-----
 
The '''DUP'''operator creates a [[00610.htm|''Duplicated-ExpressionType'']]from the ''Initializer- List''enclosed in parentheses. This construct can be used to create arrays of information during data allocation.
 
 
-----
 
[[00267.htm|''Attribute-Expression'']]'''DUP ('''''Initializer-List''''')''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
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=== Related Information ===
 
[[00264.htm|Description]]
 
[[00265.htm|Constraints]]
 
[[00266.htm|Examples]]
 
[[[00262.htm|prev]]][[[00264.htm|next]]][[[00261.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00267.htm|''Attribute-Expression'']]'''DUP ('''''Initializer-List''''')''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
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=== Description ===
 
The '''DUP'''operator creates a [[00610.htm|''Duplicated-ExpressionType'']]from the ''Initializer- List''enclosed in parentheses. This construct can be used to create arrays of information during data allocation.
 
[[[00264.htm|prev]]][[[00266.htm|next]]][[[00261.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The left hand operand of the '''DUP'''operator must evaluate to an [[00599.htm|''Absolute- ExpressionType'']].
 
Each [[00258.htm|''Duplicative-Expression'']]in the ''Initializer-List''must evaluate to an [[00614.htm|''Initializer-ExpressionType'']].
 
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=== Examples ===
 
<br />
 
<pre>STR  STRUCT
  One  BYTE  0
  Two  BYTE  0
STR  ENDS
 
Array1    WORD    4  DUP  ( 1 ,  2 ,  3 ,  4 )        ;  allocates  16  words
Array2    STR    8  DUP  ( &lt; 1 ,  2 &gt; )              ;  8  structures </pre>
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=== Attribute Expression ===
 
 
-----
 
An '''''Attribute Expression''is one that optionally extracts or modifies one or more of the basic properties of its operand.'''
 
 
-----
 
''Attribute-Expression'''':'' <br />[[00287.htm|''OR-Expression'']] <br />[[00281.htm|SHORT]][[00359.htm|''Additive-Expression'']] <br />[[00270.htm|.TYPE]][[00287.htm|''OR-Expression'']] <br />[[00275.htm|OPATTR]][[00287.htm|''OR-Expression'']] <br /> <br />
 
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=== Description ===
 
An ''Attribute Expression''is one that optionally extracts or modifies one or more of the basic properties of its operand.
 
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=== Syntax ===
 
''Attribute-Expression'''':'' <br />[[00287.htm|''OR-Expression'']] <br />[[00281.htm|SHORT]][[00359.htm|''Additive-Expression'']] <br />[[00270.htm|.TYPE]][[00287.htm|''OR-Expression'']] <br />[[00275.htm|OPATTR]][[00287.htm|''OR-Expression'']] <br /> <br />
 
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=== Expression Descriptor Bitmap (.TYPE Operator) ===
 
 
-----
 
[[00273.htm|Description]]
 
[[00274.htm|Examples]]
 
 
-----
 
The '''.TYPE'''operator is considered obsolete. The [[00275.htm|OPATTR]]operator should be used instead.
 
The '''.TYPE'''operator returns a byte value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table: <br />
 
<pre>/------------------------------------------------------------------\
|7|6|5|4|3|2|1|0|BIT SET IF EXPRESSION                            |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | | | |1|Is a Direct-ExpressionType                        |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | | |1| |Is a Indirect-ExpressionType, an                  |
| | | | | | | | |Indexed-ExpressionType, or a combination of both  |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | |1| | |Is an Immediate-ExpressionType                    |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | |1| | | |Is an Indirect-ExpressionType                    |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | |1| | | | |Is a Register-ExpressionType                      |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | |1| | | | | |Was parsed and evaluated without error (no        |
| | | | | | | | |undefined symbols, etc.)                          |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| |1| | | | | | |Is relative to the SS Segment-Register            |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
|1| | | | | | | |Contains an External Reference                    |
\------------------------------------------------------------------/</pre>
 
-----
 
'''.TYPE'''[[00287.htm|''OR-Expression'']] <br /> <br />
 
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=== Related Information ===
 
[[00273.htm|Description]]
 
[[00274.htm|Examples]]
 
[[[00271.htm|prev]]][[[00273.htm|next]]][[[00270.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''.TYPE'''[[00287.htm|''OR-Expression'']] <br /> <br />
 
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=== Description ===
 
The '''.TYPE'''operator is considered obsolete. The [[00275.htm|OPATTR]]operator should be used instead.
 
The '''.TYPE'''operator returns a byte value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table: <br />
 
<pre>/------------------------------------------------------------------\
|7|6|5|4|3|2|1|0|BIT SET IF EXPRESSION                            |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | | | |1|Is a Direct-ExpressionType                        |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | | |1| |Is a Indirect-ExpressionType, an                  |
| | | | | | | | |Indexed-ExpressionType, or a combination of both  |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | | |1| | |Is an Immediate-ExpressionType                    |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | | |1| | | |Is an Indirect-ExpressionType                    |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | | |1| | | | |Is a Register-ExpressionType                      |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| | |1| | | | | |Was parsed and evaluated without error (no        |
| | | | | | | | |undefined symbols, etc.)                          |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
| |1| | | | | | |Is relative to the SS Segment-Register            |
|-+-+-+-+-+-+-+-+--------------------------------------------------|
|1| | | | | | | |Contains an External Reference                    |
\------------------------------------------------------------------/</pre>
[[[00273.htm|prev]]][[[00275.htm|next]]][[[00270.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>BumpCounter  macro  bump
  if  ( ( ( . TYPE  ( bump ) )  and  07h )  eq  04h )
      Counter  =  Counter  +  bump
  else
      . err  &lt; Non - constant  value  passed  to  BumpCounter &gt;
  endif
endm </pre>
[[[00274.htm|prev]]][[[00276.htm|next]]][[[00267.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Extended Descriptor Bitmap (OPATTR Operator) ===
 
 
-----
 
[[00278.htm|Description]]
 
[[00279.htm|Constraints]]
 
[[00280.htm|Examples]]
 
 
-----
 
The '''OPATTR'''operator returns a superset of the information returned by the [[00270.htm|. TYPE]]operator, which should be considered obsolete.
 
The '''OPATTR'''operator returns a word value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table: <br />
 
<pre>/----------------------------------------------------------------------\
|A98|7|6|5|4|3|2|1|0|BIT SET IF EXPRESSION                            |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | | | |1|Is a Direct-ExpressionType                        |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | | |1| |Is a Indirect-ExpressionType, an                  |
|  | | | | | | | | |Indexed-ExpressionType, or a combination of both  |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | |1| | |Is an Immediate-ExpressionType                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | |1| | | |Is an Indirect-ExpressionType                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | |1| | | | |Is a Register-ExpressionType                      |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | |1| | | | | |Was parsed and evaluated without error (no        |
|  | | | | | | | | |undefined symbols, etc.)                          |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | |1| | | | | | |Is relative to the SS Segment-Register            |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  |1| | | | | | | |Contains an External Reference                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|LLL| | | | | | | | |Language encoding (described below)              |
\----------------------------------------------------------------------/</pre>
The '''LLL'''field (bits 8, 9, and A) comprise an enumerated value that describes the language attribute assigned to the expression as follows:
 
''''''
 
000No language attribute used in expression <br />001C <br />010SYSCALL <br />011STDCALL <br />100PASCAL <br />101FORTRAN <br />110BASIC <br />111OPTLINK <br />
 
 
-----
 
'''OPATTR'''[[00287.htm|''OR-Expression'']] <br /> <br />
 
[[[00275.htm|prev]]][[[00277.htm|next]]][[[00275.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00278.htm|Description]]
 
[[00279.htm|Constraints]]
 
[[00280.htm|Examples]]
 
[[[00276.htm|prev]]][[[00278.htm|next]]][[[00275.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''OPATTR'''[[00287.htm|''OR-Expression'']] <br /> <br />
 
[[[00277.htm|prev]]][[[00279.htm|next]]][[[00275.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''OPATTR'''operator returns a superset of the information returned by the [[00270.htm|. TYPE]]operator, which should be considered obsolete.
 
The '''OPATTR'''operator returns a word value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table: <br />
 
<pre>/----------------------------------------------------------------------\
|A98|7|6|5|4|3|2|1|0|BIT SET IF EXPRESSION                            |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | | | |1|Is a Direct-ExpressionType                        |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | | |1| |Is a Indirect-ExpressionType, an                  |
|  | | | | | | | | |Indexed-ExpressionType, or a combination of both  |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | | |1| | |Is an Immediate-ExpressionType                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | | |1| | | |Is an Indirect-ExpressionType                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | | |1| | | | |Is a Register-ExpressionType                      |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | | |1| | | | | |Was parsed and evaluated without error (no        |
|  | | | | | | | | |undefined symbols, etc.)                          |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  | |1| | | | | | |Is relative to the SS Segment-Register            |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|  |1| | | | | | | |Contains an External Reference                    |
|---+-+-+-+-+-+-+-+-+--------------------------------------------------|
|LLL| | | | | | | | |Language encoding (described below)              |
\----------------------------------------------------------------------/</pre>
The '''LLL'''field (bits 8, 9, and A) comprise an enumerated value that describes the language attribute assigned to the expression as follows:
 
''''''
 
000No language attribute used in expression <br />001C <br />010SYSCALL <br />011STDCALL <br />100PASCAL <br />101FORTRAN <br />110BASIC <br />111OPTLINK <br />
 
[[[00278.htm|prev]]][[[00280.htm|next]]][[[00275.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
This operator is not available in [[00105.htm|M510]]mode.
 
[[[00279.htm|prev]]][[[00281.htm|next]]][[[00275.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>L _ MASK      equ  011100000000y              ;  mask  to  isolate  language  bits
L _ OPTLINK  equ  011100000000y              ;  setting  for  OptLink  calling  convention
VerifyCallBack  macro  ProcName
  if  ( ( ( OPATTR  ( ProcName ) )  and  L _ MASK )  ne  L _ OPTLINK )
      . err  &lt; Call - back  routine  must  have  OptLink  linkage &gt;
  endif
endm </pre>
[[[00280.htm|prev]]][[[00282.htm|next]]][[[00267.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Force Short Relative Address (SHORT Operator) ===
 
 
-----
 
[[00284.htm|Description]]
 
[[00285.htm|Constraints]]
 
[[00286.htm|Examples]]
 
 
-----
 
The '''SHORT'''operator forces the assembler to calculate the distance from the start of the next instruction to the target specified by the operand (given by [[00359.htm|''Additive-Expression'']]) to be less than 128 bytes away. This can cause the assembler to generate more efficient control transfer instructions when the target is a forward reference. By default, the assembler assumes that the code-relative target is of '''NEAR'''distance when the target is an unqualified forward reference.
 
 
-----
 
'''SHORT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00281.htm|prev]]][[[00283.htm|next]]][[[00281.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00284.htm|Description]]
 
[[00285.htm|Constraints]]
 
[[00286.htm|Examples]]
 
[[[00282.htm|prev]]][[[00284.htm|next]]][[[00281.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''SHORT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00283.htm|prev]]][[[00285.htm|next]]][[[00281.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SHORT'''operator forces the assembler to calculate the distance from the start of the next instruction to the target specified by the operand (given by [[00359.htm|''Additive-Expression'']]) to be less than 128 bytes away. This can cause the assembler to generate more efficient control transfer instructions when the target is a forward reference. By default, the assembler assumes that the code-relative target is of '''NEAR'''distance when the target is an unqualified forward reference.
 
[[[00284.htm|prev]]][[[00286.htm|next]]][[[00281.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The [[00359.htm|''Additive-Expression'']]must evaluate to a [[00602.htm|''Direct-ExpressionType'']].
 
[[[00285.htm|prev]]][[[00287.htm|next]]][[[00281.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  JMP    Forward                ;  target  unknown ,  NEAR  jump  generated
  JMP    SHORT  Forward          ;  force  SHORT  encoding
  .
  .                      ;  fewer  than  128  bytes  of  instructions
  .
Forward :                        ;  definition  of  target </pre>
[[[00286.htm|prev]]][[[00288.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise OR Expression ===
 
 
-----
 
A '''''Bitwise OR Expression''is one where an optional binary bitwise '''OR''' operation between the left and right operands is performed and the result returned.'''
 
 
-----
 
''OR-Expression'''':'' <br />[[00302.htm|''AND-Expression'']] <br />''OR-Expression''[[00290.htm|OR]][[00302.htm|''AND-Expression'']] <br />''OR-Expression''[[00296.htm|XOR]][[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00287.htm|prev]]][[[00289.htm|next]]][[[00287.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Bitwise OR Expression''is one where an optional binary bitwise '''OR''' operation between the left and right operands is performed and the result returned.
 
[[[00288.htm|prev]]][[[00290.htm|next]]][[[00287.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''OR-Expression'''':'' <br />[[00302.htm|''AND-Expression'']] <br />''OR-Expression''[[00290.htm|OR]][[00302.htm|''AND-Expression'']] <br />''OR-Expression''[[00296.htm|XOR]][[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00289.htm|prev]]][[[00291.htm|next]]][[[00287.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise Inclusive OR (OR Operator) ===
 
 
-----
 
[[00293.htm|Description]]
 
[[00294.htm|Constraints]]
 
[[00295.htm|Examples]]
 
 
-----
 
The '''OR'''operator performs a binary bitwise OR operation on the left and right hand operands.
 
 
-----
 
[[00287.htm|''OR-Expression'']]'''OR'''[[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00290.htm|prev]]][[[00292.htm|next]]][[[00290.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00293.htm|Description]]
 
[[00294.htm|Constraints]]
 
[[00295.htm|Examples]]
 
[[[00291.htm|prev]]][[[00293.htm|next]]][[[00290.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00287.htm|''OR-Expression'']]'''OR'''[[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00292.htm|prev]]][[[00294.htm|next]]][[[00290.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''OR'''operator performs a binary bitwise OR operation on the left and right hand operands.
 
[[[00293.htm|prev]]][[[00295.htm|next]]][[[00290.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00294.htm|prev]]][[[00296.htm|next]]][[[00290.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  One    EQU    1
  Two    EQU    2
 
  MOV    AX ,  One  OR  Two          ;  moves  3  into  AX </pre>
[[[00295.htm|prev]]][[[00297.htm|next]]][[[00287.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise Exclusive OR (XOR Operator) ===
 
 
-----
 
[[00299.htm|Description]]
 
[[00300.htm|Constraints]]
 
[[00301.htm|Examples]]
 
 
-----
 
The '''XOR'''operator performs a binary bitwise XOR operation on the left and right hand operands.
 
 
-----
 
[[00287.htm|''OR-Expression'']]'''XOR'''[[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00296.htm|prev]]][[[00298.htm|next]]][[[00296.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00299.htm|Description]]
 
[[00300.htm|Constraints]]
 
[[00301.htm|Examples]]
 
[[[00297.htm|prev]]][[[00299.htm|next]]][[[00296.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00287.htm|''OR-Expression'']]'''XOR'''[[00302.htm|''AND-Expression'']] <br /> <br />
 
[[[00298.htm|prev]]][[[00300.htm|next]]][[[00296.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''XOR'''operator performs a binary bitwise XOR operation on the left and right hand operands.
 
[[[00299.htm|prev]]][[[00301.htm|next]]][[[00296.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00300.htm|prev]]][[[00302.htm|next]]][[[00296.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Lower    EQU    0101y            ;  7h  -  binary  radix  suffix
  Upper    EQU    1100y            ;  Eh  -  binary  radix  suffix
 
  MOV    AX ,  Upper  XOR  Lower    ;  moves  1001  into  AX </pre>
[[[00301.htm|prev]]][[[00303.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise AND Expression ===
 
 
-----
 
A '''''Bitwise AND Expression''is one where an optional binary bitwise '''AND''' operation between the left and right operands is performed and the result returned.'''
 
 
-----
 
''AND-Expression'''':'' <br />[[00311.htm|''NOT-Expression'']] <br />''AND-Expression''[[00305.htm|AND]][[00311.htm|''NOT-Expression'']] <br /> <br />
 
[[[00302.htm|prev]]][[[00304.htm|next]]][[[00302.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Bitwise AND Expression''is one where an optional binary bitwise '''AND''' operation between the left and right operands is performed and the result returned.
 
[[[00303.htm|prev]]][[[00305.htm|next]]][[[00302.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''AND-Expression'''':'' <br />[[00311.htm|''NOT-Expression'']] <br />''AND-Expression''[[00305.htm|AND]][[00311.htm|''NOT-Expression'']] <br /> <br />
 
[[[00304.htm|prev]]][[[00306.htm|next]]][[[00302.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise AND (AND Operator) ===
 
 
-----
 
[[00308.htm|Description]]
 
[[00309.htm|Constraints]]
 
[[00310.htm|Examples]]
 
 
-----
 
The '''AND'''operator performs a binary bitwise AND operation on the left and right hand operands.
 
 
-----
 
[[00302.htm|''AND-Expression'']]'''AND'''[[00311.htm|''NOT-Expression'']] <br /> <br />
 
[[[00305.htm|prev]]][[[00307.htm|next]]][[[00305.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00308.htm|Description]]
 
[[00309.htm|Constraints]]
 
[[00310.htm|Examples]]
 
[[[00306.htm|prev]]][[[00308.htm|next]]][[[00305.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00302.htm|''AND-Expression'']]'''AND'''[[00311.htm|''NOT-Expression'']] <br /> <br />
 
[[[00307.htm|prev]]][[[00309.htm|next]]][[[00305.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''AND'''operator performs a binary bitwise AND operation on the left and right hand operands.
 
[[[00308.htm|prev]]][[[00310.htm|next]]][[[00305.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00309.htm|prev]]][[[00311.htm|next]]][[[00305.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Lower    EQU    0111y            ;  7h  -  binary  radix  suffix
  Upper    EQU    1110y            ;  Eh  -  binary  radix  suffix
 
  MOV    AX ,  Upper  XOR  Lower    ;  moves  0110  into  AX </pre>
[[[00310.htm|prev]]][[[00312.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise One's Complement Expression ===
 
 
-----
 
A '''''Bitwise One's Complement Expression''is one that performs an optional unary bitwise negation of its operand and returns the result.'''
 
 
-----
 
''NOT-Expression'''':'' <br />[[00320.htm|''Relational-Expression'']] <br />[[00314.htm|NOT]][[00320.htm|''Relational-Expression'']] <br /> <br />
 
[[[00311.htm|prev]]][[[00313.htm|next]]][[[00311.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Bitwise One's Complement Expression''is one that performs an optional unary bitwise negation of its operand and returns the result.
 
[[[00312.htm|prev]]][[[00314.htm|next]]][[[00311.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''NOT-Expression'''':'' <br />[[00320.htm|''Relational-Expression'']] <br />[[00314.htm|NOT]][[00320.htm|''Relational-Expression'']] <br /> <br />
 
[[[00313.htm|prev]]][[[00315.htm|next]]][[[00311.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise One's Complement (NOT Operator) ===
 
 
-----
 
[[00317.htm|Description]]
 
[[00318.htm|Constraints]]
 
[[00319.htm|Examples]]
 
 
-----
 
The '''NOT'''operator performs a unary bitwise negation on its operand.
 
 
-----
 
'''NOT'''[[00320.htm|''Relational-Expression'']] <br /> <br />
 
[[[00314.htm|prev]]][[[00316.htm|next]]][[[00314.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00317.htm|Description]]
 
[[00318.htm|Constraints]]
 
[[00319.htm|Examples]]
 
[[[00315.htm|prev]]][[[00317.htm|next]]][[[00314.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''NOT'''[[00320.htm|''Relational-Expression'']] <br /> <br />
 
[[[00316.htm|prev]]][[[00318.htm|next]]][[[00314.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''NOT'''operator performs a unary bitwise negation on its operand.
 
[[[00317.htm|prev]]][[[00319.htm|next]]][[[00314.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00318.htm|prev]]][[[00320.htm|next]]][[[00314.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Value    EQU    0111y            ;  7h  -  binary  radix  suffix
 
  MOV    EAX ,  NOT  Value          ;  moves  FFFFFFF8  into  EAX </pre>
[[[00319.htm|prev]]][[[00321.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Relational Expression ===
 
 
-----
 
A '''''Relational Expression''is one where an optional binary comparision operation between the left and right operands is performed and the result returned.'''
 
 
-----
 
''Relational-Expression'''':'' <br />[[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00323.htm|EQ]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00329.htm|NE]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00335.htm|GT]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00341.htm|GE]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00347.htm|LT]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00353.htm|LE]][[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00320.htm|prev]]][[[00322.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Relational Expression''is one where an optional binary comparision operation between the left and right operands is performed and the result returned.
 
[[[00321.htm|prev]]][[[00323.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Relational-Expression'''':'' <br />[[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00323.htm|EQ]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00329.htm|NE]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00335.htm|GT]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00341.htm|GE]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00347.htm|LT]][[00359.htm|''Additive-Expression'']] <br />''Relational-Expression''[[00353.htm|LE]][[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00322.htm|prev]]][[[00324.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Equal To (EQ Operator) ===
 
 
-----
 
[[00326.htm|Description]]
 
[[00327.htm|Constraints]]
 
[[00328.htm|Examples]]
 
 
-----
 
The '''EQ'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are equal, and false (all bits off) if they are not equal.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''EQ'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00323.htm|prev]]][[[00325.htm|next]]][[[00323.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00326.htm|Description]]
 
[[00327.htm|Constraints]]
 
[[00328.htm|Examples]]
 
[[[00324.htm|prev]]][[[00326.htm|next]]][[[00323.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''EQ'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00325.htm|prev]]][[[00327.htm|next]]][[[00323.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''EQ'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are equal, and false (all bits off) if they are not equal.
 
[[[00326.htm|prev]]][[[00328.htm|next]]][[[00323.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00327.htm|prev]]][[[00329.htm|next]]][[[00323.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  EQ  5678
      TRUE  =  1
  ELSE
      TRUE  =  0                  ;  Sets  TRUE  to  0
  ENDIF </pre>
[[[00328.htm|prev]]][[[00330.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Not Equal To (NE Operator) ===
 
 
-----
 
[[00332.htm|Description]]
 
[[00333.htm|Constraints]]
 
[[00334.htm|Examples]]
 
 
-----
 
The '''NE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are not equal, and false (all bits off) if they are equal.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''NE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00329.htm|prev]]][[[00331.htm|next]]][[[00329.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00332.htm|Description]]
 
[[00333.htm|Constraints]]
 
[[00334.htm|Examples]]
 
[[[00330.htm|prev]]][[[00332.htm|next]]][[[00329.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''NE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00331.htm|prev]]][[[00333.htm|next]]][[[00329.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''NE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are not equal, and false (all bits off) if they are equal.
 
[[[00332.htm|prev]]][[[00334.htm|next]]][[[00329.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00333.htm|prev]]][[[00335.htm|next]]][[[00329.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  NE  5678
      TRUE  =  1                  ;  Sets  TRUE  to  1
  ELSE
      TRUE  =  0
  ENDIF </pre>
[[[00334.htm|prev]]][[[00336.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Greater Than (GT Operator) ===
 
 
-----
 
[[00338.htm|Description]]
 
[[00339.htm|Constraints]]
 
[[00340.htm|Examples]]
 
 
-----
 
The '''GT'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than the right operand, and false (all bits off) if it is not.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''GT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00335.htm|prev]]][[[00337.htm|next]]][[[00335.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00338.htm|Description]]
 
[[00339.htm|Constraints]]
 
[[00340.htm|Examples]]
 
[[[00336.htm|prev]]][[[00338.htm|next]]][[[00335.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''GT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00337.htm|prev]]][[[00339.htm|next]]][[[00335.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''GT'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than the right operand, and false (all bits off) if it is not.
 
[[[00338.htm|prev]]][[[00340.htm|next]]][[[00335.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00339.htm|prev]]][[[00341.htm|next]]][[[00335.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  GT  5678
      TRUE  =  1
  ELSE
      TRUE  =  0                  ;  Sets  TRUE  to  0
  ENDIF </pre>
[[[00340.htm|prev]]][[[00342.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Greater Than or Equal To (GE Operator) ===
 
 
-----
 
[[00344.htm|Description]]
 
[[00345.htm|Constraints]]
 
[[00346.htm|Examples]]
 
 
-----
 
The '''GE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than or equal to the right operand, and false (all bits off) if it is not.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''GE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00341.htm|prev]]][[[00343.htm|next]]][[[00341.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00344.htm|Description]]
 
[[00345.htm|Constraints]]
 
[[00346.htm|Examples]]
 
[[[00342.htm|prev]]][[[00344.htm|next]]][[[00341.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''GE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00343.htm|prev]]][[[00345.htm|next]]][[[00341.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''GE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than or equal to the right operand, and false (all bits off) if it is not.
 
[[[00344.htm|prev]]][[[00346.htm|next]]][[[00341.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00345.htm|prev]]][[[00347.htm|next]]][[[00341.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  GE  1234
      TRUE  =  1                  ;  Sets  TRUE  to  1
  ELSE
      TRUE  =  0
  ENDIF </pre>
[[[00346.htm|prev]]][[[00348.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Less Than (LT Operator) ===
 
 
-----
 
[[00350.htm|Description]]
 
[[00351.htm|Constraints]]
 
[[00352.htm|Examples]]
 
 
-----
 
The '''LT'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than the right operand, and false (all bits off) if it is not.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''LT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00347.htm|prev]]][[[00349.htm|next]]][[[00347.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00350.htm|Description]]
 
[[00351.htm|Constraints]]
 
[[00352.htm|Examples]]
 
[[[00348.htm|prev]]][[[00350.htm|next]]][[[00347.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''LT'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00349.htm|prev]]][[[00351.htm|next]]][[[00347.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LT'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than the right operand, and false (all bits off) if it is not.
 
[[[00350.htm|prev]]][[[00352.htm|next]]][[[00347.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00351.htm|prev]]][[[00353.htm|next]]][[[00347.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  LT  5678
      TRUE  =  1                  ;  Sets  TRUE  to  1
  ELSE
      TRUE  =  0
  ENDIF </pre>
[[[00352.htm|prev]]][[[00354.htm|next]]][[[00320.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Less Than or Equal To (LE Operator) ===
 
 
-----
 
[[00356.htm|Description]]
 
[[00357.htm|Constraints]]
 
[[00358.htm|Examples]]
 
 
-----
 
The '''LE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than or equal to the right operand, and false (all bits off) if it is not.
 
 
-----
 
[[00320.htm|''Relational-Expression'']]'''LE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00353.htm|prev]]][[[00355.htm|next]]][[[00353.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00356.htm|Description]]
 
[[00357.htm|Constraints]]
 
[[00358.htm|Examples]]
 
[[[00354.htm|prev]]][[[00356.htm|next]]][[[00353.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00320.htm|''Relational-Expression'']]'''LE'''[[00359.htm|''Additive-Expression'']] <br /> <br />
 
[[[00355.htm|prev]]][[[00357.htm|next]]][[[00353.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LE'''operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than or equal to the right operand, and false (all bits off) if it is not.
 
[[[00356.htm|prev]]][[[00358.htm|next]]][[[00353.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00357.htm|prev]]][[[00359.htm|next]]][[[00353.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  IF  1234  LE  1234
      TRUE  =  1                  ;  Sets  TRUE  to  1
  ELSE
      TRUE  =  0
  ENDIF </pre>
[[[00358.htm|prev]]][[[00360.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Additive Expression ===
 
 
-----
 
A '''''Additive Expression''is one where an optional binary additive arithmetic operation between the left and right operands is performed and the result returned.'''
 
 
-----
 
''Additive-Expression'''':'' <br />[[00374.htm|''Multiplicative-Expression'']] <br />''Additive-Expression''[[00362.htm|+]][[00374.htm|''Multiplicative-Expression'']] <br />''Additive-Expression''[[00368.htm|-]][[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00359.htm|prev]]][[[00361.htm|next]]][[[00359.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Additive Expression''is one where an optional binary additive arithmetic operation between the left and right operands is performed and the result returned.
 
[[[00360.htm|prev]]][[[00362.htm|next]]][[[00359.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Additive-Expression'''':'' <br />[[00374.htm|''Multiplicative-Expression'']] <br />''Additive-Expression''[[00362.htm|+]][[00374.htm|''Multiplicative-Expression'']] <br />''Additive-Expression''[[00368.htm|-]][[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00361.htm|prev]]][[[00363.htm|next]]][[[00359.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Addition (+ Operator) ===
 
 
-----
 
[[00365.htm|Description]]
 
[[00366.htm|Constraints]]
 
[[00367.htm|Examples]]
 
 
-----
 
The '''+'''operator performs a binary addition operation on the left and right hand operands, and returns the result.
 
 
-----
 
[[00359.htm|''Additive-Expression'']]'''+'''[[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00362.htm|prev]]][[[00364.htm|next]]][[[00362.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00365.htm|Description]]
 
[[00366.htm|Constraints]]
 
[[00367.htm|Examples]]
 
[[[00363.htm|prev]]][[[00365.htm|next]]][[[00362.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00359.htm|''Additive-Expression'']]'''+'''[[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00364.htm|prev]]][[[00366.htm|next]]][[[00362.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''+'''operator performs a binary addition operation on the left and right hand operands, and returns the result.
 
[[[00365.htm|prev]]][[[00367.htm|next]]][[[00362.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
One of the operands must evaluate to a [[00600.htm|''Constant-ExpressionType'']]. If one of the operands references an external identifier, then the other operand must be a [[00600.htm|''Constant-ExpressionType'']]without an external reference. Both operands must be of scalar type.
 
[[[00366.htm|prev]]][[[00368.htm|next]]][[[00362.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  100  +  11              ;  sets  VALUE  to  111 </pre>
[[[00367.htm|prev]]][[[00369.htm|next]]][[[00359.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Subtraction (- Operator) ===
 
 
-----
 
[[00371.htm|Description]]
 
[[00372.htm|Constraints]]
 
[[00373.htm|Examples]]
 
 
-----
 
The '''-'''operator performs a binary subtraction operation on the left and right hand operands, and returns the result.
 
 
-----
 
[[00359.htm|''Additive-Expression'']]'''-'''[[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00368.htm|prev]]][[[00370.htm|next]]][[[00368.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00371.htm|Description]]
 
[[00372.htm|Constraints]]
 
[[00373.htm|Examples]]
 
[[[00369.htm|prev]]][[[00371.htm|next]]][[[00368.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00359.htm|''Additive-Expression'']]'''-'''[[00374.htm|''Multiplicative-Expression'']] <br /> <br />
 
[[[00370.htm|prev]]][[[00372.htm|next]]][[[00368.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''-'''operator performs a binary subtraction operation on the left and right hand operands, and returns the result.
 
[[[00371.htm|prev]]][[[00373.htm|next]]][[[00368.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The right operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']]and reference no external identifiers. If both operands are relocatable, they must reside within the same segment, in which case the result is converted to a [[00599.htm|''Absolute-ExpressionType'']]. Both operands must be of scalar type.
 
[[[00372.htm|prev]]][[[00374.htm|next]]][[[00368.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  111  -  11              ;  sets  VALUE  to  100 </pre>
[[[00373.htm|prev]]][[[00375.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Multiplicative Expression ===
 
 
-----
 
A '''''Multiplicative Expression''is one where an optional binary multiplicative arithmetic operation between the left and right operands is performed and the result returned.'''
 
 
-----
 
''Multiplicative-Expression'''':'' <br />[[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00377.htm|*]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00383.htm|/]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00389.htm|MOD]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00395.htm|SHL]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00401.htm|SHR]][[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00374.htm|prev]]][[[00376.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Multiplicative Expression''is one where an optional binary multiplicative arithmetic operation between the left and right operands is performed and the result returned.
 
[[[00375.htm|prev]]][[[00377.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Multiplicative-Expression'''':'' <br />[[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00377.htm|*]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00383.htm|/]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00389.htm|MOD]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00395.htm|SHL]][[00407.htm|''Narrowed-Expression'']] <br />''Multiplicative-Expression''[[00401.htm|SHR]][[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00376.htm|prev]]][[[00378.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Multiplication (* Operator) ===
 
 
-----
 
[[00380.htm|Description]]
 
[[00381.htm|Constraints]]
 
[[00382.htm|Examples]]
 
 
-----
 
The '''*'''operator performs a binary multiplication operation on the left and right hand operands, and returns the result.
 
 
-----
 
[[00374.htm|''Multiplicative-Expression'']]'''*'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00377.htm|prev]]][[[00379.htm|next]]][[[00377.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00380.htm|Description]]
 
[[00381.htm|Constraints]]
 
[[00382.htm|Examples]]
 
[[[00378.htm|prev]]][[[00380.htm|next]]][[[00377.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00374.htm|''Multiplicative-Expression'']]'''*'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00379.htm|prev]]][[[00381.htm|next]]][[[00377.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''*'''operator performs a binary multiplication operation on the left and right hand operands, and returns the result.
 
[[[00380.htm|prev]]][[[00382.htm|next]]][[[00377.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00381.htm|prev]]][[[00383.htm|next]]][[[00377.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  9  *  3                ;  sets  VALUE  to  27 </pre>
[[[00382.htm|prev]]][[[00384.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Division (/ Operator) ===
 
 
-----
 
[[00386.htm|Description]]
 
[[00387.htm|Constraints]]
 
[[00388.htm|Examples]]
 
 
-----
 
The '''/'''operator performs a binary division operation on the left and right hand operands, and returns the result.
 
 
-----
 
[[00374.htm|''Multiplicative-Expression'']]'''/'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00383.htm|prev]]][[[00385.htm|next]]][[[00383.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00386.htm|Description]]
 
[[00387.htm|Constraints]]
 
[[00388.htm|Examples]]
 
[[[00384.htm|prev]]][[[00386.htm|next]]][[[00383.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00374.htm|''Multiplicative-Expression'']]'''/'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00385.htm|prev]]][[[00387.htm|next]]][[[00383.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''/'''operator performs a binary division operation on the left and right hand operands, and returns the result.
 
[[[00386.htm|prev]]][[[00388.htm|next]]][[[00383.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00387.htm|prev]]][[[00389.htm|next]]][[[00383.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  27  /  9                ;  sets  VALUE  to  3 </pre>
[[[00388.htm|prev]]][[[00390.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Remainder (MOD Operator) ===
 
 
-----
 
[[00392.htm|Description]]
 
[[00393.htm|Constraints]]
 
[[00394.htm|Examples]]
 
 
-----
 
The '''MOD'''operator performs a binary modulus division operation on the left and right hand operands, and returns the remainder as the result.
 
 
-----
 
[[00374.htm|''Multiplicative-Expression'']]'''MOD'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00389.htm|prev]]][[[00391.htm|next]]][[[00389.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00392.htm|Description]]
 
[[00393.htm|Constraints]]
 
[[00394.htm|Examples]]
 
[[[00390.htm|prev]]][[[00392.htm|next]]][[[00389.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00374.htm|''Multiplicative-Expression'']]'''MOD'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00391.htm|prev]]][[[00393.htm|next]]][[[00389.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''MOD'''operator performs a binary modulus division operation on the left and right hand operands, and returns the remainder as the result.
 
[[[00392.htm|prev]]][[[00394.htm|next]]][[[00389.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00393.htm|prev]]][[[00395.htm|next]]][[[00389.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  18  MOD  4              ;  sets  VALUE  to  2 </pre>
[[[00394.htm|prev]]][[[00396.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise Left Shift (SHL Operator) ===
 
 
-----
 
[[00398.htm|Description]]
 
[[00399.htm|Constraints]]
 
[[00400.htm|Examples]]
 
 
-----
 
The '''SHL'''operator shifts the bits in the left hand operand to the left by the number of bits specified in the right hand operand, and returns the result.
 
 
-----
 
[[00374.htm|''Multiplicative-Expression'']]'''SHL'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00395.htm|prev]]][[[00397.htm|next]]][[[00395.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00398.htm|Description]]
 
[[00399.htm|Constraints]]
 
[[00400.htm|Examples]]
 
[[[00396.htm|prev]]][[[00398.htm|next]]][[[00395.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00374.htm|''Multiplicative-Expression'']]'''SHL'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00397.htm|prev]]][[[00399.htm|next]]][[[00395.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SHL'''operator shifts the bits in the left hand operand to the left by the number of bits specified in the right hand operand, and returns the result.
 
[[[00398.htm|prev]]][[[00400.htm|next]]][[[00395.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00399.htm|prev]]][[[00401.htm|next]]][[[00395.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  1111y  SHL  4          ;  sets  VALUE  to  11110000y </pre>
[[[00400.htm|prev]]][[[00402.htm|next]]][[[00374.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Bitwise Right Shift (SHR Operator) ===
 
 
-----
 
[[00404.htm|Description]]
 
[[00405.htm|Constraints]]
 
[[00406.htm|Examples]]
 
 
-----
 
The '''SHR'''operator shifts the bits in the left hand operand to the right by the number of bits specified in the right hand operand, and returns the result.
 
 
-----
 
[[00374.htm|''Multiplicative-Expression'']]'''SHR'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00401.htm|prev]]][[[00403.htm|next]]][[[00401.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00404.htm|Description]]
 
[[00405.htm|Constraints]]
 
[[00406.htm|Examples]]
 
[[[00402.htm|prev]]][[[00404.htm|next]]][[[00401.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00374.htm|''Multiplicative-Expression'']]'''SHR'''[[00407.htm|''Narrowed-Expression'']] <br /> <br />
 
[[[00403.htm|prev]]][[[00405.htm|next]]][[[00401.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SHR'''operator shifts the bits in the left hand operand to the right by the number of bits specified in the right hand operand, and returns the result.
 
[[[00404.htm|prev]]][[[00406.htm|next]]][[[00401.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Each operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00405.htm|prev]]][[[00407.htm|next]]][[[00401.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  VALUE  =  11110000y  SHR  4          ;  sets  VALUE  to  00001111y </pre>
[[[00406.htm|prev]]][[[00408.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Narrowed Expression ===
 
 
-----
 
A '''''Narrowed Expression''is one that performs an optional unary narrowing operation on its operand and returns the result.'''
 
 
-----
 
''Narrowed-Expression'''':'' <br />[[00434.htm|''Cast-Expression'']] <br />[[00410.htm|HIGH]][[00434.htm|''Cast-Expression'']] <br />[[00416.htm|HIGHWORD]][[00434.htm|''Cast-Expression'']] <br />[[00422.htm|LOW]][[00434.htm|''Cast-Expression'']] <br />[[00428.htm|LOWWORD]][[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00407.htm|prev]]][[[00409.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Narrowed Expression''is one that performs an optional unary narrowing operation on its operand and returns the result.
 
[[[00408.htm|prev]]][[[00410.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Narrowed-Expression'''':'' <br />[[00434.htm|''Cast-Expression'']] <br />[[00410.htm|HIGH]][[00434.htm|''Cast-Expression'']] <br />[[00416.htm|HIGHWORD]][[00434.htm|''Cast-Expression'']] <br />[[00422.htm|LOW]][[00434.htm|''Cast-Expression'']] <br />[[00428.htm|LOWWORD]][[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00409.htm|prev]]][[[00411.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Upper 8 Bits of WORD Expression (HIGH Operator) ===
 
 
-----
 
[[00413.htm|Description]]
 
[[00414.htm|Constraints]]
 
[[00415.htm|Examples]]
 
 
-----
 
The '''HIGH'''operator returns the upper 8 bits of a 16-bit expression. Only bits 8-15 are returned, even if the magnitude of the operand exceeds 16 bits.
 
 
-----
 
'''HIGH'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00410.htm|prev]]][[[00412.htm|next]]][[[00410.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00413.htm|Description]]
 
[[00414.htm|Constraints]]
 
[[00415.htm|Examples]]
 
[[[00411.htm|prev]]][[[00413.htm|next]]][[[00410.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''HIGH'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00412.htm|prev]]][[[00414.htm|next]]][[[00410.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''HIGH'''operator returns the upper 8 bits of a 16-bit expression. Only bits 8-15 are returned, even if the magnitude of the operand exceeds 16 bits.
 
[[[00413.htm|prev]]][[[00415.htm|next]]][[[00410.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00414.htm|prev]]][[[00416.htm|next]]][[[00410.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  FIRST    =  1234h
  SECOND  =  HIGH  FIRST          ;  Sets  SECOND  to  12h </pre>
[[[00415.htm|prev]]][[[00417.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Upper 16 Bits of DWORD Expression (HIGHWORD Operator) ===
 
 
-----
 
[[00419.htm|Description]]
 
[[00420.htm|Constraints]]
 
[[00421.htm|Examples]]
 
 
-----
 
The '''HIGHWORD'''operator returns the upper 16 bits of a 32-bit expression. Only bits 16-31 are returned, even if the magnitude of the operand exceeds 32 bits.
 
 
-----
 
'''HIGHWORD'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00416.htm|prev]]][[[00418.htm|next]]][[[00416.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00419.htm|Description]]
 
[[00420.htm|Constraints]]
 
[[00421.htm|Examples]]
 
[[[00417.htm|prev]]][[[00419.htm|next]]][[[00416.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''HIGHWORD'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00418.htm|prev]]][[[00420.htm|next]]][[[00416.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''HIGHWORD'''operator returns the upper 16 bits of a 32-bit expression. Only bits 16-31 are returned, even if the magnitude of the operand exceeds 32 bits.
 
[[[00419.htm|prev]]][[[00421.htm|next]]][[[00416.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
This operator is not available in [[00105.htm|M510]]mode.
 
[[[00420.htm|prev]]][[[00422.htm|next]]][[[00416.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  FIRST    =  12345678h
  SECOND  =  HIGHWORD  FIRST      ;  Sets  SECOND  to  1234h </pre>
[[[00421.htm|prev]]][[[00423.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Lower 8 Bits of WORD Expression (LOW Operator) ===
 
 
-----
 
[[00425.htm|Description]]
 
[[00426.htm|Constraints]]
 
[[00427.htm|Examples]]
 
 
-----
 
The '''LOW'''operator returns the lower 8 bits of its operand.
 
 
-----
 
'''LOW'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00422.htm|prev]]][[[00424.htm|next]]][[[00422.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00425.htm|Description]]
 
[[00426.htm|Constraints]]
 
[[00427.htm|Examples]]
 
[[[00423.htm|prev]]][[[00425.htm|next]]][[[00422.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''LOW'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00424.htm|prev]]][[[00426.htm|next]]][[[00422.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LOW'''operator returns the lower 8 bits of its operand.
 
[[[00425.htm|prev]]][[[00427.htm|next]]][[[00422.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00426.htm|prev]]][[[00428.htm|next]]][[[00422.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  FIRST    =  1234h
  SECOND  =  LOW  FIRST          ;  Sets  SECOND  to  34h </pre>
[[[00427.htm|prev]]][[[00429.htm|next]]][[[00407.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Lower 16 Bits of DWORD Expression (LOWWORD Operator) ===
 
 
-----
 
[[00431.htm|Description]]
 
[[00432.htm|Constraints]]
 
[[00433.htm|Examples]]
 
 
-----
 
The '''LOWWORD'''operator returns the lower 16 bits of its operand.
 
 
-----
 
'''LOWWORD'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00428.htm|prev]]][[[00430.htm|next]]][[[00428.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00431.htm|Description]]
 
[[00432.htm|Constraints]]
 
[[00433.htm|Examples]]
 
[[[00429.htm|prev]]][[[00431.htm|next]]][[[00428.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''LOWWORD'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00430.htm|prev]]][[[00432.htm|next]]][[[00428.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LOWWORD'''operator returns the lower 16 bits of its operand.
 
[[[00431.htm|prev]]][[[00433.htm|next]]][[[00428.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
This operator is not available in [[00105.htm|M510]]mode.
 
[[[00432.htm|prev]]][[[00434.htm|next]]][[[00428.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  FIRST    =  12345678h
  SECOND  =  LOWWORD  FIRST      ;  Sets  SECOND  to  5678h </pre>
[[[00433.htm|prev]]][[[00435.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Conversion Expression ===
 
 
-----
 
A '''''Type Conversion Expression''is one that performs an optional type conversion operation on its operand and returns the result.'''
 
 
-----
 
''Cast-Expression'''':'' <br />[[00473.htm|''Element-Selection-Expression'']] <br />[[00437.htm|OFFSET]]''Cast-Expression'' <br />[[00443.htm|SEG]]''Cast-Expression'' <br />[[00449.htm|THIS]][[00473.htm|''Element-Selection-Expression'']] <br />[[00455.htm|TYPE]][[00473.htm|''Element-Selection-Expression'']] <br />''Cast-Expression''[[00461.htm|PTR]]''Cast-Expression'' <br />''Cast-Expression''[[00467.htm|:]]''Cast-Expression'' <br /> <br />
 
[[[00434.htm|prev]]][[[00436.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Type Conversion Expression''is one that performs an optional type conversion operation on its operand and returns the result.
 
[[[00435.htm|prev]]][[[00437.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Cast-Expression'''':'' <br />[[00473.htm|''Element-Selection-Expression'']] <br />[[00437.htm|OFFSET]]''Cast-Expression'' <br />[[00443.htm|SEG]]''Cast-Expression'' <br />[[00449.htm|THIS]][[00473.htm|''Element-Selection-Expression'']] <br />[[00455.htm|TYPE]][[00473.htm|''Element-Selection-Expression'']] <br />''Cast-Expression''[[00461.htm|PTR]]''Cast-Expression'' <br />''Cast-Expression''[[00467.htm|:]]''Cast-Expression'' <br /> <br />
 
[[[00436.htm|prev]]][[[00438.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Address Offset (OFFSET Operator) ===
 
 
-----
 
[[00440.htm|Description]]
 
[[00441.htm|Constraints]]
 
[[00442.htm|Examples]]
 
 
-----
 
The '''OFFSET'''operator returns the offset portion of its operand. For relocatable values, this is the offset into the segment or group to which the expression is relative.
 
 
-----
 
'''OFFSET'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00437.htm|prev]]][[[00439.htm|next]]][[[00437.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00440.htm|Description]]
 
[[00441.htm|Constraints]]
 
[[00442.htm|Examples]]
 
[[[00438.htm|prev]]][[[00440.htm|next]]][[[00437.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''OFFSET'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00439.htm|prev]]][[[00441.htm|next]]][[[00437.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''OFFSET'''operator returns the offset portion of its operand. For relocatable values, this is the offset into the segment or group to which the expression is relative.
 
[[[00440.htm|prev]]][[[00442.htm|next]]][[[00437.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand may evaluate to any one of the following [[00596.htm|''ExpressionType'']]''s'''':''
 
�[[00599.htm|''Absolute-ExpressionType'']] <br />�[[00600.htm|''Constant-ExpressionType'']] <br />�[[00601.htm|''Immediate-ExpressionType'']] <br />�[[00602.htm|''Direct-ExpressionType'']] <br />�[[00603.htm|''Indirect-ExpressionType'']] <br />
 
[[[00441.htm|prev]]][[[00443.htm|next]]][[[00437.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  CodeLabel :
              MOV  AX , CodeLabel            ;  illegal ,  no  data  at  address
              MOV  AX , OFFSET  CodeLabel    ;  we  want  the  address  itself </pre>
[[[00442.htm|prev]]][[[00444.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Address Segment (SEG Operator) ===
 
 
-----
 
[[00446.htm|Description]]
 
[[00447.htm|Constraints]]
 
[[00448.htm|Examples]]
 
 
-----
 
The '''SEG'''operator returns the segment or group to which a relocatable expression is relative.
 
 
-----
 
'''SEG'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00443.htm|prev]]][[[00445.htm|next]]][[[00443.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00446.htm|Description]]
 
[[00447.htm|Constraints]]
 
[[00448.htm|Examples]]
 
[[[00444.htm|prev]]][[[00446.htm|next]]][[[00443.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''SEG'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00445.htm|prev]]][[[00447.htm|next]]][[[00443.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SEG'''operator returns the segment or group to which a relocatable expression is relative.
 
[[[00446.htm|prev]]][[[00448.htm|next]]][[[00443.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to one of the following [[00596.htm|''ExpressionType'']]''s'''':''
 
�[[00601.htm|''Immediate-ExpressionType'']] <br />�[[00602.htm|''Direct-ExpressionType'']] <br />�[[00603.htm|''Indirect-ExpressionType'']] <br />�[[00604.htm|''Indexed-ExpressionType'']] <br />
 
[[[00447.htm|prev]]][[[00449.htm|next]]][[[00443.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>DATA      SEGMENT
Stuff    DB      ?
        MOV    AX ,  SEG  Stuff    ;  This  construct  is
        MOV    AX ,  DATA        ;  equivalent  to  this
DATA      ENDS </pre>
[[[00448.htm|prev]]][[[00450.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Address Alias (THIS Operator) ===
 
 
-----
 
[[00452.htm|Description]]
 
[[00453.htm|Constraints]]
 
[[00454.htm|Examples]]
 
 
-----
 
The '''THIS'''operator returns an operand whose:
 
�[[00589.htm|''Relative Frame'']]attribute is set to that of the current segment <br />�[[00588.htm|''Displacement'']]attribute is set to the current location counter <br />�[[00595.htm|''Type Declaration'']]attribute is set to that of the expression given by the [[00473.htm|''Element-Selection-Expression'']]operand. <br />
 
 
-----
 
'''THIS'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00449.htm|prev]]][[[00451.htm|next]]][[[00449.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00452.htm|Description]]
 
[[00453.htm|Constraints]]
 
[[00454.htm|Examples]]
 
[[[00450.htm|prev]]][[[00452.htm|next]]][[[00449.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''THIS'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00451.htm|prev]]][[[00453.htm|next]]][[[00449.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''THIS'''operator returns an operand whose:
 
�[[00589.htm|''Relative Frame'']]attribute is set to that of the current segment <br />�[[00588.htm|''Displacement'']]attribute is set to the current location counter <br />�[[00595.htm|''Type Declaration'']]attribute is set to that of the expression given by the [[00473.htm|''Element-Selection-Expression'']]operand. <br />
 
[[[00452.htm|prev]]][[[00454.htm|next]]][[[00449.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00608.htm|''Type-ExpressionType'']].
 
[[[00453.htm|prev]]][[[00455.htm|next]]][[[00449.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>DATA      SEGMENT
 
ALIAS    EQU    THIS  BYTE        ;  reference  this  address  as  a  byte
Stuff    DB      ?
 
        MOV    AL ,  ALIAS        ;  This  construct  is
        MOV    AL ,  Stuff        ;  equivalent  to  this
 
DATA      ENDS </pre>
[[[00454.htm|prev]]][[[00456.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Datatype Extraction (TYPE Operator) ===
 
 
-----
 
[[00458.htm|Description]]
 
[[00459.htm|Constraints]]
 
[[00460.htm|Examples]]
 
 
-----
 
The '''TYPE'''operator returns the [[00608.htm|''Type-ExpressionType'']]attribute of its operand.
 
 
-----
 
'''TYPE'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00455.htm|prev]]][[[00457.htm|next]]][[[00455.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00458.htm|Description]]
 
[[00459.htm|Constraints]]
 
[[00460.htm|Examples]]
 
[[[00456.htm|prev]]][[[00458.htm|next]]][[[00455.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''TYPE'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00457.htm|prev]]][[[00459.htm|next]]][[[00455.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''TYPE'''operator returns the [[00608.htm|''Type-ExpressionType'']]attribute of its operand.
 
[[[00458.htm|prev]]][[[00460.htm|next]]][[[00455.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
None
 
[[[00459.htm|prev]]][[[00461.htm|next]]][[[00455.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>CODE      SEGMENT
        ASSUME  CS : CODE , DS : CODE
Stuff    DB      ?                                ;  TYPE  Stuff  is  BYTE
        MOV    [ BX ] ,  ( TYPE  Stuff )  PTR  1        ;  stores  1  as  a  BYTE  at  [ BX ]
CODE      ENDS </pre>
[[[00460.htm|prev]]][[[00462.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Conversion (PTR Operator) ===
 
 
-----
 
[[00464.htm|Description]]
 
[[00465.htm|Constraints]]
 
[[00466.htm|Examples]]
 
 
-----
 
The '''PTR'''operator converts the right operand to the type specified by the left operand.
 
 
-----
 
[[00434.htm|''Cast-Expression'']]'''PTR'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00461.htm|prev]]][[[00463.htm|next]]][[[00461.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00464.htm|Description]]
 
[[00465.htm|Constraints]]
 
[[00466.htm|Examples]]
 
[[[00462.htm|prev]]][[[00464.htm|next]]][[[00461.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00434.htm|''Cast-Expression'']]'''PTR'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00463.htm|prev]]][[[00465.htm|next]]][[[00461.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''PTR'''operator converts the right operand to the type specified by the left operand.
 
[[[00464.htm|prev]]][[[00466.htm|next]]][[[00461.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The left operand must be a [[00608.htm|''Type-ExpressionType'']].
 
[[[00465.htm|prev]]][[[00467.htm|next]]][[[00461.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>CODE      SEGMENT
        MOV    BYTE  PTR  [ BX ] ,  1      ;  stores  1  as  a  BYTE  at  [ BX ]
CODE      ENDS </pre>
[[[00466.htm|prev]]][[[00468.htm|next]]][[[00434.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Segment Override (: Operator) ===
 
 
-----
 
[[00470.htm|Description]]
 
[[00471.htm|Constraints]]
 
[[00472.htm|Examples]]
 
 
-----
 
The ''':'''(colon) operator forces the right operand to have the [[00589.htm|''Relative Frame'']] attribute of the left operand.
 
 
-----
 
[[00434.htm|''Cast-Expression'']]''':'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00467.htm|prev]]][[[00469.htm|next]]][[[00467.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00470.htm|Description]]
 
[[00471.htm|Constraints]]
 
[[00472.htm|Examples]]
 
[[[00468.htm|prev]]][[[00470.htm|next]]][[[00467.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00434.htm|''Cast-Expression'']]''':'''[[00434.htm|''Cast-Expression'']] <br /> <br />
 
[[[00469.htm|prev]]][[[00471.htm|next]]][[[00467.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The ''':'''(colon) operator forces the right operand to have the [[00589.htm|''Relative Frame'']] attribute of the left operand.
 
[[[00470.htm|prev]]][[[00472.htm|next]]][[[00467.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The left operand must evaluate to one of the following [[00596.htm|''ExpressionType'']]''s'''':''
 
�[[00605.htm|''Register-ExpressionType'']]where the [[00591.htm|''Register Value'']]attribute is that of a [[00122.htm|''Segment-Register'']] <br />�[[00601.htm|''Immediate-ExpressionType'']]where the [[00589.htm|''Relative Frame'']]attribute is that of a [[00162.htm|''GroupName'']]or [[00170.htm|''SegmentName'']]. <br />
 
[[[00471.htm|prev]]][[[00473.htm|next]]][[[00467.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>DATA      SEGMENT
Variable  DW      ?
DATA      ENDS
 
DGROUP    GROUP  DATA ,  CODE
 
CODE      SEGMENT
  ASSUME  CS : CODE ,  DS : DGROUP
  MOV      AX ,  DGROUP : Variable        ;  insure  Variable  is  relative  to  DGROUP
  ASSUME  DS : NOTHING
  MOV      BX ,  CS : Variable              ;  access  Variable  through  CS  register
CODE      ENDS </pre>
[[[00472.htm|prev]]][[[00474.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Element Selection Expression ===
 
 
-----
 
A '''''Element Selection Expression''is one that optionally selects a specific element of its operand and returns a reference to it.'''
 
 
-----
 
''Element-Selection-Expression'''':'' <br />[[00488.htm|''Sign-Expression'']] <br />''Element-Selection-Expression''[[00476.htm|[]]''Sign-Expression''[[00476.htm|00476.htm]]] <br />''Element-Selection-Expression''[[00482.htm|.]]''Sign-Expression'' <br /> <br />
 
[[[00473.htm|prev]]][[[00475.htm|next]]][[[00473.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Element Selection Expression''is one that optionally selects a specific element of its operand and returns a reference to it.
 
[[[00474.htm|prev]]][[[00476.htm|next]]][[[00473.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Element-Selection-Expression'''':'' <br />[[00488.htm|''Sign-Expression'']] <br />''Element-Selection-Expression''[[00476.htm|[]]''Sign-Expression''[[00476.htm|00476.htm]]] <br />''Element-Selection-Expression''[[00482.htm|.]]''Sign-Expression'' <br /> <br />
 
[[[00475.htm|prev]]][[[00477.htm|next]]][[[00473.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Subscript ([] Operator) ===
 
 
-----
 
[[00479.htm|Description]]
 
[[00480.htm|Constraints]]
 
[[00481.htm|Examples]]
 
 
-----
 
The '''[]'''binary operator performs a subscripting (or ''indexing'') operation between the operand to the left of the brackets and the operand enclosed within the brackets. This is a simple additive operation of '''BYTE''' granularity; the arithmetic performed is not influenced by the [[00587.htm|''Operand Size'']] of either operand.
 
The syntax for this operator describes a binary operation between the left hand expression and the bracketed expression. The bracketed expression is also subject to the same operations performed during the processing of a standalone [[00573.htm|''Indirected-Expression'']]as described in the section on [[00503.htm|''Primary- Expression'']]''s''.
 
 
-----
 
[[00473.htm|''Element-Selection-Expression'']]'''['''[[00488.htm|''Sign-Expression'']]''']''' <br /> <br />
 
[[[00476.htm|prev]]][[[00478.htm|next]]][[[00476.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00479.htm|Description]]
 
[[00480.htm|Constraints]]
 
[[00481.htm|Examples]]
 
[[[00477.htm|prev]]][[[00479.htm|next]]][[[00476.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00473.htm|''Element-Selection-Expression'']]'''['''[[00488.htm|''Sign-Expression'']]''']''' <br /> <br />
 
[[[00478.htm|prev]]][[[00480.htm|next]]][[[00476.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''[]'''binary operator performs a subscripting (or ''indexing'') operation between the operand to the left of the brackets and the operand enclosed within the brackets. This is a simple additive operation of '''BYTE''' granularity; the arithmetic performed is not influenced by the [[00587.htm|''Operand Size'']] of either operand.
 
The syntax for this operator describes a binary operation between the left hand expression and the bracketed expression. The bracketed expression is also subject to the same operations performed during the processing of a standalone [[00573.htm|''Indirected-Expression'']]as described in the section on [[00503.htm|''Primary- Expression'']]''s''.
 
[[[00479.htm|prev]]][[[00481.htm|next]]][[[00476.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Only one of the operands may specify a relocatable value.
 
[[[00480.htm|prev]]][[[00482.htm|next]]][[[00476.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>CODE      SEGMENT
          ASSUME  CS : CODE ,  DS : CODE
 
Value      DB    0                        ;  Value [ 0 ]
          DB    1                        ;  Value [ 1 ]
          DB    2                        ;  Value [ 2 ]
          DB    3                        ;  Value [ 3 ]
          DB    4                        ;  Value [ 4 ]
 
  MOV      AL ,  Value [ 3 ]                ;  load  AL  with  the  fourth  byte  at  Value  ( 3 )
  MOV      BX ,  offset  Value            ;  get  address  of  Value
  MOV      AL ,  [ BX ] [ 1 ] [ 2 ]              ;  also  gets  the  fourth  byte  ( 3 )
 
CODE      ENDS </pre>
[[[00481.htm|prev]]][[[00483.htm|next]]][[[00473.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Structure/Union Field Selection (. Operator) ===
 
 
-----
 
[[00485.htm|Description]]
 
[[00486.htm|Constraints]]
 
[[00487.htm|Examples]]
 
 
-----
 
The '''.'''(period) operator selects a structure or union field entry. It adds the left and right hand operands together and returns the result. The left operand should be an [[00603.htm|''Indirect-ExpressionType'']], [[00604.htm|''Indexed-ExpressionType'']], or [[00608.htm|''Type-ExpressionType'']]whose [[00595.htm|''Type Declaration'']]attribute resolves to that of a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union-TypeName'']]. The right operand should refer to a [[00158.htm|''FieldName'']]defined within the referenced type.
 
The [[00587.htm|''Operand Size'']]attribute of the result depends on the operands involved. If both operands have an operand size, a [[00160.htm|''Structure-FieldName'']]appearing as the right hand operand would override the operand size of the left operand and would dictate the operand size of the resulting expression.
 
 
-----
 
[[00473.htm|''Element-Selection-Expression'']]'''.'''[[00488.htm|''Sign-Expression'']] <br /> <br />
 
[[[00482.htm|prev]]][[[00484.htm|next]]][[[00482.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00485.htm|Description]]
 
[[00486.htm|Constraints]]
 
[[00487.htm|Examples]]
 
[[[00483.htm|prev]]][[[00485.htm|next]]][[[00482.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
[[00473.htm|''Element-Selection-Expression'']]'''.'''[[00488.htm|''Sign-Expression'']] <br /> <br />
 
[[[00484.htm|prev]]][[[00486.htm|next]]][[[00482.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''.'''(period) operator selects a structure or union field entry. It adds the left and right hand operands together and returns the result. The left operand should be an [[00603.htm|''Indirect-ExpressionType'']], [[00604.htm|''Indexed-ExpressionType'']], or [[00608.htm|''Type-ExpressionType'']]whose [[00595.htm|''Type Declaration'']]attribute resolves to that of a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union-TypeName'']]. The right operand should refer to a [[00158.htm|''FieldName'']]defined within the referenced type.
 
The [[00587.htm|''Operand Size'']]attribute of the result depends on the operands involved. If both operands have an operand size, a [[00160.htm|''Structure-FieldName'']]appearing as the right hand operand would override the operand size of the left operand and would dictate the operand size of the resulting expression.
 
[[[00485.htm|prev]]][[[00487.htm|next]]][[[00482.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Only one of the operands may specify a relocatable value.
 
[[[00486.htm|prev]]][[[00488.htm|next]]][[[00482.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>Number  STRUC
  One    DB  1
  Two    DW  2
Number  ENDS
 
  ;  The  following  line  is  only  allowed  in  MASM  5 . 10  mode  ( OPTION  OLDSTRUCTS )
 
  MOV  AX , [ BX ] . Two        ;  BX  points  to  a  &quot; Number &quot; ,  get  the  &quot; Two &quot;  entry
 
  ;  In  other  modes ,  &quot; Two &quot;  is  private  to  the  &quot; Number &quot;  structure  type ,  so
  ;  one  of  the  following  methods  are  required :
 
  MOV  AX , ( Number  PTR  [ BX ] ) . Two          ;  Explicit  override
  MOV  AX , [ BX ]  +  Number . Two                ;  Fully  qualified  reference
  ASSUME  BX : Number                        ;  Associate  BX  with  &quot; Number &quot;
  MOV  AX , [ BX ] . Two                          ;    then  original  syntax  is  allowed
</pre>
[[[00487.htm|prev]]][[[00489.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Unary Arithmetic Expression ===
 
 
-----
 
A '''''Unary Arithmetic Expression''is one that optionally alters the sign of its operand and returns the result.'''
 
 
-----
 
''Sign-Expression'''':'' <br />[[00503.htm|''Primary-Expression'']] <br />[[00491.htm|-]][[00503.htm|''Primary-Expression'']] <br />[[00497.htm|+]][[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00488.htm|prev]]][[[00490.htm|next]]][[[00488.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Unary Arithmetic Expression''is one that optionally alters the sign of its operand and returns the result.
 
[[[00489.htm|prev]]][[[00491.htm|next]]][[[00488.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Sign-Expression'''':'' <br />[[00503.htm|''Primary-Expression'']] <br />[[00491.htm|-]][[00503.htm|''Primary-Expression'']] <br />[[00497.htm|+]][[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00490.htm|prev]]][[[00492.htm|next]]][[[00488.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Unary Minus (- Operator) ===
 
 
-----
 
[[00494.htm|Description]]
 
[[00495.htm|Constraints]]
 
[[00496.htm|Examples]]
 
 
-----
 
The '''-'''operator makes its operand into a negative number and returns the result.
 
 
-----
 
'''-'''[[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00491.htm|prev]]][[[00493.htm|next]]][[[00491.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00494.htm|Description]]
 
[[00495.htm|Constraints]]
 
[[00496.htm|Examples]]
 
[[[00492.htm|prev]]][[[00494.htm|next]]][[[00491.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''-'''[[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00493.htm|prev]]][[[00495.htm|next]]][[[00491.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''-'''operator makes its operand into a negative number and returns the result.
 
[[[00494.htm|prev]]][[[00496.htm|next]]][[[00491.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00495.htm|prev]]][[[00497.htm|next]]][[[00491.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Value    EQU    1
 
  MOV    AX , - Value    ;  move  - 1  into  AX </pre>
[[[00496.htm|prev]]][[[00498.htm|next]]][[[00488.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Unary Plus (+ Operator) ===
 
 
-----
 
[[00500.htm|Description]]
 
[[00501.htm|Constraints]]
 
[[00502.htm|Examples]]
 
 
-----
 
The '''+'''operator returns its operand.
 
 
-----
 
'''+'''[[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00497.htm|prev]]][[[00499.htm|next]]][[[00497.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00500.htm|Description]]
 
[[00501.htm|Constraints]]
 
[[00502.htm|Examples]]
 
[[[00498.htm|prev]]][[[00500.htm|next]]][[[00497.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''+'''[[00503.htm|''Primary-Expression'']] <br /> <br />
 
[[[00499.htm|prev]]][[[00501.htm|next]]][[[00497.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''+'''operator returns its operand.
 
[[[00500.htm|prev]]][[[00502.htm|next]]][[[00497.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00600.htm|''Constant-ExpressionType'']].
 
[[[00501.htm|prev]]][[[00503.htm|next]]][[[00497.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Value    EQU    1
  MOV    AX , + Value    ;  move  1  into  AX </pre>
[[[00502.htm|prev]]][[[00504.htm|next]]][[[00255.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Primary Expression ===
 
 
-----
 
A '''''Primary Expression''is one that returns an expression operand.'''
 
 
-----
 
''Primary-Expression'''':'' <br />[[00506.htm|''Literal-Operand'']] <br />[[00516.htm|''Record-Constant'']] <br />[[00527.htm|''Identifier-Operand'']] <br />[[00522.htm|''Register-Operand'']] <br />[[00532.htm|''Integral-TypeName-Operand'']] <br />[[00511.htm|''Value-Substitution-Operand'']] <br />[[00537.htm|LENGTH]][[00527.htm|''Identifier-Operand'']] <br />[[00542.htm|LENGTHOF]][[00527.htm|''Identifier-Operand'']] <br />[[00548.htm|MASK]][[00527.htm|''Identifier-Operand'']] <br />[[00553.htm|SIZE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00558.htm|SIZEOF]][[00473.htm|''Element-Selection-Expression'']] <br />[[00563.htm|WIDTH]][[00527.htm|''Identifier-Operand'']] <br />[[00568.htm|''Parenthesized-Expression'']] <br />[[00573.htm|''Indirected-Expression'']] <br />[[00579.htm|''Compound-Initializer'']] <br /> <br />
 
[[[00503.htm|prev]]][[[00505.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Primary Expression''is one that returns an expression operand.
 
[[[00504.htm|prev]]][[[00506.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Primary-Expression'''':'' <br />[[00506.htm|''Literal-Operand'']] <br />[[00516.htm|''Record-Constant'']] <br />[[00527.htm|''Identifier-Operand'']] <br />[[00522.htm|''Register-Operand'']] <br />[[00532.htm|''Integral-TypeName-Operand'']] <br />[[00511.htm|''Value-Substitution-Operand'']] <br />[[00537.htm|LENGTH]][[00527.htm|''Identifier-Operand'']] <br />[[00542.htm|LENGTHOF]][[00527.htm|''Identifier-Operand'']] <br />[[00548.htm|MASK]][[00527.htm|''Identifier-Operand'']] <br />[[00553.htm|SIZE]][[00473.htm|''Element-Selection-Expression'']] <br />[[00558.htm|SIZEOF]][[00473.htm|''Element-Selection-Expression'']] <br />[[00563.htm|WIDTH]][[00527.htm|''Identifier-Operand'']] <br />[[00568.htm|''Parenthesized-Expression'']] <br />[[00573.htm|''Indirected-Expression'']] <br />[[00579.htm|''Compound-Initializer'']] <br /> <br />
 
[[[00505.htm|prev]]][[[00507.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Literal Operand ===
 
 
-----
 
[[00509.htm|Description]]
 
[[00510.htm|Constraints]]
 
 
-----
 
The assembler accepts several types of literal values as operands within expressions. ''Literal-Operand''''s''are converted to [[00596.htm|''ExpressionType'']]''s''according to the following table: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Floating-Point-Literal  |Floating-Point-ExpressionType                        |
|------------------------+------------------------------------------------------|
|Integer-Literal        |Absolute-ExpressionType                              |
|------------------------+------------------------------------------------------|
|String-Literal          |Absolute-ExpressionType if the string length is less  |
|                        |than or equal to the current Address Size; a          |
|                        |String-ExpressionType otherwise.                      |
\-------------------------------------------------------------------------------/</pre>
The context where the expression is used determines whether or not a particular type of literal is legal.
 
 
-----
 
''Literal-Operand'''':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />
 
[[[00506.htm|prev]]][[[00508.htm|next]]][[[00506.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00509.htm|Description]]
 
[[00510.htm|Constraints]]
 
[[[00507.htm|prev]]][[[00509.htm|next]]][[[00506.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Literal-Operand'''':'' <br />[[00226.htm|''Floating-Point-Literal'']] <br />[[00202.htm|''Integer-Literal'']] <br />[[00241.htm|''String-Literal'']] <br /> <br />
 
[[[00508.htm|prev]]][[[00510.htm|next]]][[[00506.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The assembler accepts several types of literal values as operands within expressions. ''Literal-Operand''''s''are converted to [[00596.htm|''ExpressionType'']]''s''according to the following table: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Floating-Point-Literal  |Floating-Point-ExpressionType                        |
|------------------------+------------------------------------------------------|
|Integer-Literal        |Absolute-ExpressionType                              |
|------------------------+------------------------------------------------------|
|String-Literal          |Absolute-ExpressionType if the string length is less  |
|                        |than or equal to the current Address Size; a          |
|                        |String-ExpressionType otherwise.                      |
\-------------------------------------------------------------------------------/</pre>
The context where the expression is used determines whether or not a particular type of literal is legal.
 
[[[00509.htm|prev]]][[[00511.htm|next]]][[[00506.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
Arithmetic operations cannot be performed on [[00226.htm|''Floating-Point-Literal'']]''s'', thus they cannot be the operand of a unary or binary operator.
 
[[[00510.htm|prev]]][[[00512.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Value Substitution Operand ===
 
 
-----
 
[[00514.htm|Description]]
 
[[00515.htm|Constraints]]
 
 
-----
 
These operands are used to retrieve specialized values that are calculated internally by the assembler.
 
The '''FLAT'''operator returns an expression whose [[00589.htm|''Relative Frame'']]is set to that of the predefined FLAT pseudo-group.
 
 
-----
 
''Value-Substitution-Operand'''':'' <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />'''FLAT''' <br /> <br />
 
[[[00511.htm|prev]]][[[00513.htm|next]]][[[00511.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00514.htm|Description]]
 
[[00515.htm|Constraints]]
 
[[[00512.htm|prev]]][[[00514.htm|next]]][[[00511.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Value-Substitution-Operand'''':'' <br />[[00134.htm|''Anonymous-Label-Alias'']] <br />[[00137.htm|''Location-Counter-Alias'']] <br />[[00140.htm|''Indeterminate-Value-Alias'']] <br />'''FLAT''' <br /> <br />
 
[[[00513.htm|prev]]][[[00515.htm|next]]][[[00511.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
These operands are used to retrieve specialized values that are calculated internally by the assembler.
 
The '''FLAT'''operator returns an expression whose [[00589.htm|''Relative Frame'']]is set to that of the predefined FLAT pseudo-group.
 
[[[00514.htm|prev]]][[[00516.htm|next]]][[[00511.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The '''FLAT'''operand is only active when a 32-bit processor has been selected.
 
[[[00515.htm|prev]]][[[00517.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Record Constant Operand ===
 
 
-----
 
[[00519.htm|Description]]
 
[[00520.htm|Constraints]]
 
[[00521.htm|Examples]]
 
 
-----
 
A ''Record-Constant''provides a method of calculating a single numeric result value from a list of [[00159.htm|''Record-FieldName'']]values, and combining them together according to the definition of the [[00172.htm|''Record-TypeName'']]given by the [[00527.htm|''Identifier- Operand'']]. The result value is a [[00600.htm|''Constant-ExpressionType'']]suitable for use as an instruction operand, or for assigning to a record variable.
 
The [[00172.htm|''Record-TypeName'']]given by the [[00527.htm|''Identifier-Operand'']]determines how the ''Field-List''will be evaluated. The [[00267.htm|''Attribute-Expression'']]entries are position-dependent, and are matched with the corresponding [[00159.htm|''Record-FieldName'']] entries from the [[00172.htm|''Record-TypeName'']]definition to determine their width and shift values. [[00267.htm|''Attribute-Expression'']]entries may be omitted, in which case the default values from the record definition are used in the calculation.
 
 
-----
 
''Record-Constant'''':'' <br />[[00527.htm|''Identifier-Operand'']]'''&lt;'''''Field-List'''''&gt;''' <br />[[00527.htm|''Identifier-Operand'']]'''{'''''Field-List'''''}''' <br /> <br />''Field-List:'' <br />[[00267.htm|''Attribute-Expression'']] <br />''Field-List''''','''[[00267.htm|''Attribute-Expression'']] <br /> <br />
 
[[[00516.htm|prev]]][[[00518.htm|next]]][[[00516.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00519.htm|Description]]
 
[[00520.htm|Constraints]]
 
[[00521.htm|Examples]]
 
[[[00517.htm|prev]]][[[00519.htm|next]]][[[00516.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Record-Constant'''':'' <br />[[00527.htm|''Identifier-Operand'']]'''&lt;'''''Field-List'''''&gt;''' <br />[[00527.htm|''Identifier-Operand'']]'''{'''''Field-List'''''}''' <br /> <br />''Field-List:'' <br />[[00267.htm|''Attribute-Expression'']] <br />''Field-List''''','''[[00267.htm|''Attribute-Expression'']] <br /> <br />
 
[[[00518.htm|prev]]][[[00520.htm|next]]][[[00516.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Record-Constant''provides a method of calculating a single numeric result value from a list of [[00159.htm|''Record-FieldName'']]values, and combining them together according to the definition of the [[00172.htm|''Record-TypeName'']]given by the [[00527.htm|''Identifier- Operand'']]. The result value is a [[00600.htm|''Constant-ExpressionType'']]suitable for use as an instruction operand, or for assigning to a record variable.
 
The [[00172.htm|''Record-TypeName'']]given by the [[00527.htm|''Identifier-Operand'']]determines how the ''Field-List''will be evaluated. The [[00267.htm|''Attribute-Expression'']]entries are position-dependent, and are matched with the corresponding [[00159.htm|''Record-FieldName'']] entries from the [[00172.htm|''Record-TypeName'']]definition to determine their width and shift values. [[00267.htm|''Attribute-Expression'']]entries may be omitted, in which case the default values from the record definition are used in the calculation.
 
[[[00519.htm|prev]]][[[00521.htm|next]]][[[00516.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The [[00527.htm|''Identifier-Operand'']]must resolve to a [[00172.htm|''Record-TypeName'']].
 
[[[00520.htm|prev]]][[[00522.htm|next]]][[[00516.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>DATE _ T  record  Year  : 7  =  0 ,    ;  0  is  1980
                Month : 4  =  1 ,    ;  January
                Day    : 5  =  1    ;  1st
 
CODE  SEGMENT
  mov  AX ,  DATE _ T  &lt; &gt;                            ;  January  1st ,  1980
  mov  AX ,  DATE _ T  &lt; 1996 - 1980 ,  12 ,  25 &gt;        ;  Christmas ,  1996
  mov  AX ,  DATE _ T  &lt; 10h ,  0Ch ,  19h &gt;              ;  equivalent  values  in  hex
  mov  AX ,  DATE _ T  &lt; 10000y ,  1100y ,  11001y &gt;    ;  equivalent  values  in  binary
  mov  AX ,  2199h                                ;  equivalent  value  manually  coded
  mov  AX ,  0010000110011001y                  ;  and  in  binary
;          YYYYYYYMMMMDDDDD
CODE  ENDS </pre>
[[[00521.htm|prev]]][[[00523.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Register Operand ===
 
 
-----
 
[[00525.htm|Description]]
 
[[00526.htm|Constraints]]
 
 
-----
 
Processor registers are valid expression operands. The context where the expression is used determines the allowable register operands.
 
 
-----
 
''Register-Operand'''':'' <br />[[00122.htm|''Processor-Register'']] <br /> <br />
 
[[[00522.htm|prev]]][[[00524.htm|next]]][[[00522.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00525.htm|Description]]
 
[[00526.htm|Constraints]]
 
[[[00523.htm|prev]]][[[00525.htm|next]]][[[00522.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Register-Operand'''':'' <br />[[00122.htm|''Processor-Register'']] <br /> <br />
 
[[[00524.htm|prev]]][[[00526.htm|next]]][[[00522.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Processor registers are valid expression operands. The context where the expression is used determines the allowable register operands.
 
[[[00525.htm|prev]]][[[00527.htm|next]]][[[00522.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The currently selected processor dictates whether or not a register is visible to the expression evaluator.
 
[[[00526.htm|prev]]][[[00528.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Identifier Operand ===
 
 
-----
 
[[00530.htm|Description]]
 
[[00531.htm|Constraints]]
 
 
-----
 
When an [[00149.htm|''Identifier'']]is used in an expression, it returns a value according to its [[00152.htm|''Identifier-Type'']], as shown in the following table: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Identifier-Type    |VALUE RETURNED                                            |
|--------------------+----------------------------------------------------------|
|Numeric-EquateName  |The value originally assigned to the equate.              |
|--------------------+----------------------------------------------------------|
|Structure-FieldName |The offset in bytes from the beginning of the structure.  |
|--------------------+----------------------------------------------------------|
|Union-FieldName    |The offset in bytes from the beginning of the union      |
|                    |(always 0).                                              |
|--------------------+----------------------------------------------------------|
|Record-FieldName    |The shift-count required to reach the field within the    |
|                    |record.                                                  |
|--------------------+----------------------------------------------------------|
|Record-TypeName    |The mask-value that isolates defined record fields from  |
|                    |undefined fields.                                        |
|--------------------+----------------------------------------------------------|
|Structure-TypeName  |Zero if mode is M510, otherwise the size of the structure |
|                    |in bytes (the operand size of the structure type).        |
|--------------------+----------------------------------------------------------|
|Union-TypeName      |The size of the union in bytes (the operand size of the  |
|                    |union type).                                              |
|--------------------+----------------------------------------------------------|
|Typedef-TypeName    |The operand size of the underlying data-type represented  |
|                    |by the Typedef-TypeName.                                  |
|--------------------+----------------------------------------------------------|
|GroupName          |A Relative Frame attribute that represents the group, and |
|                    |a Displacement value of zero.                            |
|--------------------+----------------------------------------------------------|
|SegmentName        |A Relative Frame attribute that represents the segment (or|
|                    |the group to which it belongs), and a Displacement value  |
|                    |of zero if the mode is M510, or the current segment offset|
|                    |otherwise.                                                |
|--------------------+----------------------------------------------------------|
|LabelName          |The Relative Frame attribute where the label is defined,  |
|                    |and the segment offset value of the label.                |
\-------------------------------------------------------------------------------/</pre>
 
-----
 
''Identifier-Operand'''':'' <br />[[00149.htm|''Identifier'']] <br /> <br />
 
[[[00527.htm|prev]]][[[00529.htm|next]]][[[00527.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00530.htm|Description]]
 
[[00531.htm|Constraints]]
 
[[[00528.htm|prev]]][[[00530.htm|next]]][[[00527.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Identifier-Operand'''':'' <br />[[00149.htm|''Identifier'']] <br /> <br />
 
[[[00529.htm|prev]]][[[00531.htm|next]]][[[00527.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
When an [[00149.htm|''Identifier'']]is used in an expression, it returns a value according to its [[00152.htm|''Identifier-Type'']], as shown in the following table: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Identifier-Type    |VALUE RETURNED                                            |
|--------------------+----------------------------------------------------------|
|Numeric-EquateName  |The value originally assigned to the equate.              |
|--------------------+----------------------------------------------------------|
|Structure-FieldName |The offset in bytes from the beginning of the structure.  |
|--------------------+----------------------------------------------------------|
|Union-FieldName    |The offset in bytes from the beginning of the union      |
|                    |(always 0).                                              |
|--------------------+----------------------------------------------------------|
|Record-FieldName    |The shift-count required to reach the field within the    |
|                    |record.                                                  |
|--------------------+----------------------------------------------------------|
|Record-TypeName    |The mask-value that isolates defined record fields from  |
|                    |undefined fields.                                        |
|--------------------+----------------------------------------------------------|
|Structure-TypeName  |Zero if mode is M510, otherwise the size of the structure |
|                    |in bytes (the operand size of the structure type).        |
|--------------------+----------------------------------------------------------|
|Union-TypeName      |The size of the union in bytes (the operand size of the  |
|                    |union type).                                              |
|--------------------+----------------------------------------------------------|
|Typedef-TypeName    |The operand size of the underlying data-type represented  |
|                    |by the Typedef-TypeName.                                  |
|--------------------+----------------------------------------------------------|
|GroupName          |A Relative Frame attribute that represents the group, and |
|                    |a Displacement value of zero.                            |
|--------------------+----------------------------------------------------------|
|SegmentName        |A Relative Frame attribute that represents the segment (or|
|                    |the group to which it belongs), and a Displacement value  |
|                    |of zero if the mode is M510, or the current segment offset|
|                    |otherwise.                                                |
|--------------------+----------------------------------------------------------|
|LabelName          |The Relative Frame attribute where the label is defined,  |
|                    |and the segment offset value of the label.                |
\-------------------------------------------------------------------------------/</pre>
[[[00530.htm|prev]]][[[00532.htm|next]]][[[00527.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The [[00149.htm|''Identifier'']]must resolve to one of the following [[00152.htm|''Identifier-Type'']]''s'''':''
 
�[[00156.htm|''Numeric-EquateName'']] <br />�[[00158.htm|''FieldName'']] <br />�[[00162.htm|''GroupName'']] <br />�[[00163.htm|''LabelName'']] <br />�[[00170.htm|''SegmentName'']] <br />�[[00171.htm|''UserDefined-TypeName'']] <br />
 
[[[00531.htm|prev]]][[[00533.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Integral Type-Name Operand ===
 
 
-----
 
[[00535.htm|Description]]
 
[[00536.htm|Constraints]]
 
 
-----
 
When an ''Integral-TypeName-Operand''is used in an expression, it is converted to a [[00608.htm|''Type-ExpressionType'']]. If used in a numeric context, the following numeric values are returned: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Integral-TypeName-Operand|VALUE RETURNED                                      |
|-------------------------+-----------------------------------------------------|
|Scalar-TypeName          |The operand-size of the type in bytes.              |
|-------------------------+-----------------------------------------------------|
|Distance-TypeName        |If mode is M510, NEAR returns FFFF, and FAR returns  |
|                        |FFFE.  Otherwise, NEAR and FAR are resolved and the  |
|                        |values returned are:  NEAR16=FF02, NEAR32=FF04,      |
|                        |FAR16=FF05, FAR32=FF06.                              |
\-------------------------------------------------------------------------------/</pre>
 
-----
 
''Integral-TypeName-Operand'''':'' <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br /> <br />
 
[[[00532.htm|prev]]][[[00534.htm|next]]][[[00532.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00535.htm|Description]]
 
[[00536.htm|Constraints]]
 
[[[00533.htm|prev]]][[[00535.htm|next]]][[[00532.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Integral-TypeName-Operand'''':'' <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00128.htm|''Distance-TypeName'']] <br /> <br />
 
[[[00534.htm|prev]]][[[00536.htm|next]]][[[00532.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
When an ''Integral-TypeName-Operand''is used in an expression, it is converted to a [[00608.htm|''Type-ExpressionType'']]. If used in a numeric context, the following numeric values are returned: <br />
 
<pre>/-------------------------------------------------------------------------------\
|Integral-TypeName-Operand|VALUE RETURNED                                      |
|-------------------------+-----------------------------------------------------|
|Scalar-TypeName          |The operand-size of the type in bytes.              |
|-------------------------+-----------------------------------------------------|
|Distance-TypeName        |If mode is M510, NEAR returns FFFF, and FAR returns  |
|                        |FFFE.  Otherwise, NEAR and FAR are resolved and the  |
|                        |values returned are:  NEAR16=FF02, NEAR32=FF04,      |
|                        |FAR16=FF05, FAR32=FF06.                              |
\-------------------------------------------------------------------------------/</pre>
[[[00535.htm|prev]]][[[00537.htm|next]]][[[00532.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The '''NEAR32'''and '''FAR32'''keywords are only valid if a 32-bit processor has been selected.
 
[[[00536.htm|prev]]][[[00538.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Number of Data Elements (LENGTH Operator) ===
 
 
-----
 
[[00540.htm|Description]]
 
[[00541.htm|Constraints]]
 
 
-----
 
The '''LENGTH'''operator returns the number of data elements allocated to the operand. When applied to a variable initialized with a series of comma- separated expressions (elements), only the length of the first element is considered.
 
 
-----
 
'''LENGTH'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00537.htm|prev]]][[[00539.htm|next]]][[[00537.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00540.htm|Description]]
 
[[00541.htm|Constraints]]
 
[[[00538.htm|prev]]][[[00540.htm|next]]][[[00537.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''LENGTH'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00539.htm|prev]]][[[00541.htm|next]]][[[00537.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LENGTH'''operator returns the number of data elements allocated to the operand. When applied to a variable initialized with a series of comma- separated expressions (elements), only the length of the first element is considered.
 
[[[00540.htm|prev]]][[[00542.htm|next]]][[[00537.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00167.htm|''Data-LabelName'']].
 
[[[00541.htm|prev]]][[[00543.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Number of Data Elements (LENGTHOF Operator) ===
 
 
-----
 
[[00545.htm|Description]]
 
[[00546.htm|Constraints]]
 
 
-----
 
The '''LENGTHOF'''operator returns the number of data elements allocated to the operand.
 
 
-----
 
'''LENGTHOF'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00542.htm|prev]]][[[00544.htm|next]]][[[00542.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00545.htm|Description]]
 
[[00546.htm|Constraints]]
 
[[[00543.htm|prev]]][[[00545.htm|next]]][[[00542.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''LENGTHOF'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00544.htm|prev]]][[[00546.htm|next]]][[[00542.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''LENGTHOF'''operator returns the number of data elements allocated to the operand.
 
[[[00545.htm|prev]]][[[00547.htm|next]]][[[00542.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The operand must evaluate to a [[00167.htm|''Data-LabelName'']].
 
This operator is not available in [[00105.htm|M510]]mode.
 
[[[00546.htm|prev]]][[[00548.htm|next]]][[[00542.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
&lt;none&gt;
 
[[[00547.htm|prev]]][[[00549.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Record or Field Bit-Mask (MASK Operator) ===
 
 
-----
 
[[00551.htm|Description]]
 
[[00552.htm|Constraints]]
 
 
-----
 
The '''MASK'''operator returns the bit mask required to isolate a field within a record.
 
 
-----
 
'''MASK'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00548.htm|prev]]][[[00550.htm|next]]][[[00548.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00551.htm|Description]]
 
[[00552.htm|Constraints]]
 
[[[00549.htm|prev]]][[[00551.htm|next]]][[[00548.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''MASK'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00550.htm|prev]]][[[00552.htm|next]]][[[00548.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''MASK'''operator returns the bit mask required to isolate a field within a record.
 
[[[00551.htm|prev]]][[[00553.htm|next]]][[[00548.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The [[00527.htm|''Identifier-Operand'']]must resolve to a [[00172.htm|''Record-TypeName'']]or [[00159.htm|''Record- FieldName'']]; otherwise the result is zero.
 
[[[00552.htm|prev]]][[[00554.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Size of Variable in Bytes (SIZE Operator) ===
 
 
-----
 
[[00556.htm|Description]]
 
[[00557.htm|Constraints]]
 
 
-----
 
The '''SIZE'''operator returns the number of bytes allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the size of the first element is considered.
 
 
-----
 
'''SIZE'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00553.htm|prev]]][[[00555.htm|next]]][[[00553.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00556.htm|Description]]
 
[[00557.htm|Constraints]]
 
[[[00554.htm|prev]]][[[00556.htm|next]]][[[00553.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''SIZE'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00555.htm|prev]]][[[00557.htm|next]]][[[00553.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SIZE'''operator returns the number of bytes allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the size of the first element is considered.
 
[[[00556.htm|prev]]][[[00558.htm|next]]][[[00553.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
None
 
[[[00557.htm|prev]]][[[00559.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Size of Variable in Bytes (SIZEOF Operator) ===
 
 
-----
 
[[00561.htm|Description]]
 
[[00562.htm|Constraints]]
 
 
-----
 
The '''SIZEOF'''operator returns the number of bytes allocated to the operand.
 
 
-----
 
'''SIZEOF'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00558.htm|prev]]][[[00560.htm|next]]][[[00558.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00561.htm|Description]]
 
[[00562.htm|Constraints]]
 
[[[00559.htm|prev]]][[[00561.htm|next]]][[[00558.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''SIZEOF'''[[00473.htm|''Element-Selection-Expression'']] <br /> <br />
 
[[[00560.htm|prev]]][[[00562.htm|next]]][[[00558.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''SIZEOF'''operator returns the number of bytes allocated to the operand.
 
[[[00561.htm|prev]]][[[00563.htm|next]]][[[00558.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
This operator is not available in [[00105.htm|M510]]mode.
 
[[[00562.htm|prev]]][[[00564.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Record or Field Width (WIDTH Operator) ===
 
 
-----
 
[[00566.htm|Description]]
 
[[00567.htm|Constraints]]
 
 
-----
 
The '''WIDTH'''operator returns the width of a record or a record field name.
 
 
-----
 
'''WIDTH'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00563.htm|prev]]][[[00565.htm|next]]][[[00563.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00566.htm|Description]]
 
[[00567.htm|Constraints]]
 
[[[00564.htm|prev]]][[[00566.htm|next]]][[[00563.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
'''WIDTH'''[[00527.htm|''Identifier-Operand'']] <br /> <br />
 
[[[00565.htm|prev]]][[[00567.htm|next]]][[[00563.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''WIDTH'''operator returns the width of a record or a record field name.
 
[[[00566.htm|prev]]][[[00568.htm|next]]][[[00563.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The [[00527.htm|''Identifier-Operand'']]must resolve to a [[00172.htm|''Record-TypeName'']]or [[00159.htm|''Record- FieldName'']]; otherwise the result is zero.
 
[[[00567.htm|prev]]][[[00569.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Precedence (() Operator) ===
 
 
-----
 
[[00571.htm|Description]]
 
[[00572.htm|Examples]]
 
 
-----
 
Parentheses forces the [[00267.htm|''Attribute-Expression'']]operand to be evaluated at a higher precedence level.
 
 
-----
 
''Parenthesized-Expression'''':'' <br />'''('''[[00267.htm|''Attribute-Expression'']]''')''' <br /> <br />
 
[[[00568.htm|prev]]][[[00570.htm|next]]][[[00568.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00571.htm|Description]]
 
[[00572.htm|Examples]]
 
[[[00569.htm|prev]]][[[00571.htm|next]]][[[00568.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Parenthesized-Expression'''':'' <br />'''('''[[00267.htm|''Attribute-Expression'']]''')''' <br /> <br />
 
[[[00570.htm|prev]]][[[00572.htm|next]]][[[00568.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Parentheses forces the [[00267.htm|''Attribute-Expression'']]operand to be evaluated at a higher precedence level.
 
[[[00571.htm|prev]]][[[00573.htm|next]]][[[00568.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Value  =  2  +  3  *  4      ;  Value  =  14
  Value  =  ( 2  +  3 )  *  4    ;  Value  =  20 </pre>
[[[00572.htm|prev]]][[[00574.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Indirection ([] Operator) ===
 
 
-----
 
[[00576.htm|Description]]
 
[[00577.htm|Constraints]]
 
[[00578.htm|Examples]]
 
 
-----
 
During evaluation of the [[00267.htm|''Attribute-Expression'']], the '''[]'''('''''indirection'') operator will convert a [[00605.htm|''Register-ExpressionType'']]to a [[00604.htm|''Indexed-ExpressionType'']] by moving the [[00591.htm|''Register Value'']]attribute to either the [[00592.htm|''Base Register'']]or [[00593.htm|''Index Register'']]attribute field as appropriate for the register(s) referenced in the expression. This operation allows values contained in the processor registers to be used during effective address calculation at application run time.'''
 
 
-----
 
''Indirected-Expression'''':'' <br />'''['''[[00267.htm|''Attribute-Expression'']]''']''' <br /> <br />
 
[[[00573.htm|prev]]][[[00575.htm|next]]][[[00573.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00576.htm|Description]]
 
[[00577.htm|Constraints]]
 
[[00578.htm|Examples]]
 
[[[00574.htm|prev]]][[[00576.htm|next]]][[[00573.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Indirected-Expression'''':'' <br />'''['''[[00267.htm|''Attribute-Expression'']]''']''' <br /> <br />
 
[[[00575.htm|prev]]][[[00577.htm|next]]][[[00573.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
During evaluation of the [[00267.htm|''Attribute-Expression'']], the '''[]'''(''indirection'') operator will convert a [[00605.htm|''Register-ExpressionType'']]to a [[00604.htm|''Indexed-ExpressionType'']] by moving the [[00591.htm|''Register Value'']]attribute to either the [[00592.htm|''Base Register'']]or [[00593.htm|''Index Register'']]attribute field as appropriate for the register(s) referenced in the expression. This operation allows values contained in the processor registers to be used during effective address calculation at application run time.
 
[[[00576.htm|prev]]][[[00578.htm|next]]][[[00573.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
See the [[00604.htm|''Indexed-ExpressionType'']]section for information on registers that are valid for use in this context.
 
[[[00577.htm|prev]]][[[00579.htm|next]]][[[00573.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>CODE      SEGMENT
          ASSUME  CS : CODE ,  DS : CODE
Value      DW    0
          MOV    BX , offset  Value            ;  load  the  address  of  Value  into  BX
          MOV    [ BX ] , BX                    ;  store  the  contents  of  BX  into  the
                                          ;  memory  location  addressed  by  [ BX ]
CODE      ENDS </pre>
[[[00578.htm|prev]]][[[00580.htm|next]]][[[00503.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Compound Initializer List (&lt;&gt; Operator) ===
 
 
-----
 
[[00582.htm|Description]]
 
[[00583.htm|Examples]]
 
 
-----
 
The '''&lt;&gt;'''(or '''{}''') operator provides a way of specifying a list of expressions to be used for initializing complex (multi-field) variables such as records or structures.
 
The '''&lt;&gt;'''operator encloses a list of comma-separated expressions; individual expressions are optional, but are also positional with respect to the record or structure fields they are intended to initialize. Commas must therefore be used to maintain field positions if empty expressions are encountered in the list.
 
The initializer list itself may also be left out entirely for those cases where a variable allocation will use the default initializers provided in the record or structure definition (the '''&lt;&gt;'''or '''{}'''themselves are still required).
 
 
-----
 
''Compound-Initializer'''':'' <br />'''&lt;'''''Initializer-List'''''&gt;''' <br />'''{'''''Initializer-List'''''}''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
[[[00579.htm|prev]]][[[00581.htm|next]]][[[00579.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00582.htm|Description]]
 
[[00583.htm|Examples]]
 
[[[00580.htm|prev]]][[[00582.htm|next]]][[[00579.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Compound-Initializer'''':'' <br />'''&lt;'''''Initializer-List'''''&gt;''' <br />'''{'''''Initializer-List'''''}''' <br /> <br />''Initializer-List:'' <br />[[00258.htm|''Duplicative-Expression'']] <br />''Initializer-List''''','''[[00258.htm|''Duplicative-Expression'']] <br /> <br />
 
[[[00581.htm|prev]]][[[00583.htm|next]]][[[00579.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''&lt;&gt;'''(or '''{}''') operator provides a way of specifying a list of expressions to be used for initializing complex (multi-field) variables such as records or structures.
 
The '''&lt;&gt;'''operator encloses a list of comma-separated expressions; individual expressions are optional, but are also positional with respect to the record or structure fields they are intended to initialize. Commas must therefore be used to maintain field positions if empty expressions are encountered in the list.
 
The initializer list itself may also be left out entirely for those cases where a variable allocation will use the default initializers provided in the record or structure definition (the '''&lt;&gt;'''or '''{}'''themselves are still required).
 
[[[00582.htm|prev]]][[[00584.htm|next]]][[[00579.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  Numbers  STRUCT
    One    DB    0
    Two    DW    0
    Three  DB    0
    Four    DD    0
  Numbers  ENDS
 
First    Numbers  &lt; &gt;              ;  empty  initializer  list
Second  Numbers  &lt; 1 ,  2 ,  3 ,  4 &gt;    ;  override  all  defaults
Third    Numbers  &lt; 1 &gt;              ;  override  first  entry  only
Fourth  Numbers  &lt; 1 , , , 4 &gt;        ;  override  first  and  last  entries </pre>
[[[00583.htm|prev]]][[[00585.htm|next]]][[[00254.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Expression Evaluation ===
 
After an expression is parsed and checked for syntax errors, it is ''evaluated''. During evaluation, all calculations and conversions are performed on the operands according to the operators that are applied to them. The final result is a collection of [[00585.htm|''Expression-Attribute'']]''s'', to which an [[00596.htm|''ExpressionType'']]is assigned.
 
[[[00584.htm|prev]]][[[00586.htm|next]]][[[00584.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Expression Attributes ===
 
This section describes the ''Expression-Attribute''''s''that are associated with an expression after it is evaluated.
 
[[[00585.htm|prev]]][[[00587.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Address Size ===
 
If an expression refers to an effective address, then it also has an associated [[00797.htm|address size]]. The following [[00596.htm|''ExpressionType'']]''s''normally reference an effective address, and thus have an associated address size:
 
�[[00601.htm|''Immediate-ExpressionType'']] <br />�[[00602.htm|''Direct-ExpressionType'']] <br />�[[00603.htm|''Indirect-ExpressionType'']] <br />�[[00604.htm|''Indexed-ExpressionType'']] <br />
 
The address size can be either 2 ('''USE16''') or 4 ('''USE32'''). For an expression that references a label, the address size of the segment where the label is defined determines the address size of the expression.
 
[[[00586.htm|prev]]][[[00588.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operand Size ===
 
The ''Operand Size''of an expression can be set explicitly using the [[00461.htm|Type Conversion (PTR Operator)]], or it may be a side-effect inherited from the type of data referenced in the expression. The following table describes the operand sizes that will be assigned when an identifier is referenced in an expression: <br />
 
<pre>/-------------------------------------------------------------\
|REFERENCE                |OPERAND SIZE                      |
|-------------------------+-----------------------------------|
|8-Bit-Register          |1                                  |
|-------------------------+-----------------------------------|
|16-Bit-Register          |2                                  |
|-------------------------+-----------------------------------|
|32-Bit-Register          |4                                  |
|-------------------------+-----------------------------------|
|Segment-Register        |2                                  |
|-------------------------+-----------------------------------|
|Control-Register        |4                                  |
|-------------------------+-----------------------------------|
|Debug-Register          |4                                  |
|-------------------------+-----------------------------------|
|Test-Register            |4                                  |
|-------------------------+-----------------------------------|
|MMX-Register            |8                                  |
|-------------------------+-----------------------------------|
|Floating-Point-Register  |10                                |
|-------------------------+-----------------------------------|
|BYTE                    |1                                  |
|-------------------------+-----------------------------------|
|SBYTE                    |1                                  |
|-------------------------+-----------------------------------|
|WORD                    |2                                  |
|-------------------------+-----------------------------------|
|SWORD                    |2                                  |
|-------------------------+-----------------------------------|
|DWORD                    |4                                  |
|-------------------------+-----------------------------------|
|SDWORD                  |4                                  |
|-------------------------+-----------------------------------|
|REAL4                    |4                                  |
|-------------------------+-----------------------------------|
|FWORD                    |6                                  |
|-------------------------+-----------------------------------|
|QWORD                    |8                                  |
|-------------------------+-----------------------------------|
|REAL8                    |8                                  |
|-------------------------+-----------------------------------|
|TBYTE                    |10                                |
|-------------------------+-----------------------------------|
|REAL10                  |10                                |
|-------------------------+-----------------------------------|
|NEAR                    |2 or 4                            |
|-------------------------+-----------------------------------|
|NEAR16                  |2                                  |
|-------------------------+-----------------------------------|
|NEAR32                  |4                                  |
|-------------------------+-----------------------------------|
|FAR                      |4 or 6                            |
|-------------------------+-----------------------------------|
|FAR16                    |4                                  |
|-------------------------+-----------------------------------|
|FAR32                    |6                                  |
|-------------------------+-----------------------------------|
|Numeric-EquateName      |Inherited from equate expression  |
|-------------------------+-----------------------------------|
|GroupName                |2                                  |
|-------------------------+-----------------------------------|
|SegmentName              |2                                  |
|-------------------------+-----------------------------------|
|Code-LabelName          |SIZE (TYPE Code-LabelName)        |
|-------------------------+-----------------------------------|
|Data-LabelName          |SIZE (TYPE Data-LabelName)        |
|-------------------------+-----------------------------------|
|Structure-FieldName      |SIZE Structure-FieldName          |
|-------------------------+-----------------------------------|
|Record-TypeName          |SIZE Record-TypeName              |
|-------------------------+-----------------------------------|
|Structure-TypeName      |SIZE Structure-TypeName            |
|-------------------------+-----------------------------------|
|Union-TypeName          |SIZE Union-TypeName                |
\-------------------------------------------------------------/</pre>
The ''Operand Size''is 0 for all other identifier types.
 
[[[00587.htm|prev]]][[[00589.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Displacement ===
 
The ''Displacement''value in an expression is the final calculated value of all numeric quantities, and must be a scalar value. It may also be a reference to a relocatable address, in which case the expression will also have a [[00589.htm|''Relative Frame'']]and/or an [[00590.htm|''External Reference'']]attribute. A ''Displacement''may be used in the calculation of an effective address, either alone or in combination with a [[00592.htm|''Base Register'']]and/or an [[00593.htm|''Index Register'']].
 
[[[00588.htm|prev]]][[[00590.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Relative Frame ===
 
The ''Relative Frame''attribute will be present if the expression contains a direct or indirect reference to any of the following [[00152.htm|''Identifier-Type'']]''s'''':''
 
�[[00162.htm|''GroupName'']] <br />�[[00163.htm|''LabelName'']] <br />�[[00170.htm|''SegmentName'']] <br />
 
The ''Relative Frame''attribute indicates that the expression is relocatable, and specifies the [[00162.htm|''GroupName'']]or [[00170.htm|''SegmentName'']]to which the expression is relative.
 
[[[00589.htm|prev]]][[[00591.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== External Reference ===
 
The ''External Reference''attribute will be present if the expression references any external identifiers.
 
[[[00590.htm|prev]]][[[00592.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Register Value ===
 
The ''Register Value''attribute specifies the value of the [[00122.htm|''Processor-Register'']] referenced in a [[00605.htm|''Register-ExpressionType'']].
 
[[[00591.htm|prev]]][[[00593.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Base Register ===
 
The ''Base Register''attribute specifies the value for the base register used in an [[00604.htm|''Indexed-ExpressionType'']].
 
[[[00592.htm|prev]]][[[00594.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Index Register ===
 
The ''Index Register''attribute specifies the value for the index register used in an [[00604.htm|''Indexed-ExpressionType'']].
 
[[[00593.htm|prev]]][[[00595.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Scale Factor ===
 
The ''Scale Factor''attribute specifies the scaling value used (if any) in an [[00604.htm|''Indexed-ExpressionType'']].
 
[[[00594.htm|prev]]][[[00596.htm|next]]][[[00585.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Declaration ===
 
The ''Type Declaration''attribute specifies the type of data referenced in the expression. This is the value extracted from the expression when it is used as the left operand of the [[00461.htm|Type Conversion (PTR Operator)]].
 
[[[00595.htm|prev]]][[[00597.htm|next]]][[[00584.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Expression Types ===
 
 
-----
 
An ''ExpressionType''is assigned to every expression during evaluation. The ''ExpressionType''is used to determine whether or not an expression is legal for the context in which it is used. The type of an expression is influenced primarily by the operands that are used, but the use of expression operators also play an important part in determining the type of an expression.
 
 
-----
 
''ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00604.htm|''Indexed-ExpressionType'']] <br />[[00605.htm|''Register-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br />[[00610.htm|''Duplicated-ExpressionType'']] <br />[[00609.htm|''Compound-ExpressionType'']] <br /> <br />
 
[[[00596.htm|prev]]][[[00598.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
An ''ExpressionType''is assigned to every expression during evaluation. The ''ExpressionType''is used to determine whether or not an expression is legal for the context in which it is used. The type of an expression is influenced primarily by the operands that are used, but the use of expression operators also play an important part in determining the type of an expression.
 
[[[00597.htm|prev]]][[[00599.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Definition ===
 
''ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00604.htm|''Indexed-ExpressionType'']] <br />[[00605.htm|''Register-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br />[[00610.htm|''Duplicated-ExpressionType'']] <br />[[00609.htm|''Compound-ExpressionType'']] <br /> <br />
 
[[[00598.htm|prev]]][[[00600.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Absolute Expression Type ===
 
An ''Absolute-ExpressionType''is an expression that evaluates to an integer quantity. Its value must be representable using one of the following types of scalar data:
 
�'''BYTE''' <br />�'''SBYTE''' <br />�'''WORD''' <br />�'''SWORD''' <br />�'''DWORD''' <br />�'''SDWORD''' <br />�'''FWORD''' <br />�'''QWORD''' <br />�'''TBYTE''' <br />
 
The following restrictions apply to an ''Absolute-ExpressionType'''':''
 
�It cannot be relocatable (it may not contain references to a [[00162.htm|''GroupName'']], [[00170.htm|''SegmentName'']]or [[00163.htm|''LabelName'']]). <br />�It cannot reference any [[00590.htm|external]]symbols. <br />�It cannot contain any forward references. <br />
 
[[[00599.htm|prev]]][[[00601.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constant Expression Type ===
 
A ''Constant-ExpressionType''is an [[00599.htm|''Absolute-ExpressionType'']]with the following restrictions relaxed:
 
�It may contain forward references to identifiers defined later in the source stream. <br />�It may reference a single [[00590.htm|external]]symbol, provided that the symbol was declared in an '''EXTERN'''directive with the '''ABS'''attribute. <br />
 
[[[00600.htm|prev]]][[[00602.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Immediate Expression Type ===
 
An ''Immediate-ExpressionType''has all the properties of a [[00600.htm|''Constant- ExpressionType'']]with the following restrictions relaxed:
 
�It may contain references to a [[00162.htm|''GroupName'']], [[00170.htm|''SegmentName'']]or [[00163.htm|''LabelName'']](it may be relocatable). <br />�It may reference a relocatable [[00590.htm|external]]symbol. <br />
 
An ''Immediate-ExpressionType''must not be larger than 32 bits in magnitude; its value must be representable using one of the following types of scalar data:
 
�'''BYTE''' <br />�'''SBYTE''' <br />�'''WORD''' <br />�'''SWORD''' <br />�'''DWORD''' <br />�'''SDWORD''' <br />
 
[[[00601.htm|prev]]][[[00603.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Direct Expression Type ===
 
A ''Direct-ExpressionType''is an expression that references a [[00164.htm|''Code-LabelName'']]. It can be used directly in code-relative instructions without conversion. There is no data type associated with the address that a ''Direct- ExpressionType''represents, therefore It may not be used in a data-relative instruction without first being explicitly converted to another expression type.
 
[[[00602.htm|prev]]][[[00604.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Indirect Expression Type ===
 
An ''Indirect-ExpressionType''is an expression that references a [[00167.htm|''Data- LabelName'']]. It can be used directly in data-relative instructions without conversion to another expression type.
 
[[[00603.htm|prev]]][[[00605.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Indexed Expression Type ===
 
An ''Indexed-ExpressionType''is an expression that calculates an effective memory address using the contents of a '''''Base-Register'', an '''''Index-Register'', or both. A [[00122.htm|''Processor-Register'']]must first be converted to a ''Base-Register''or ''Index-Register''by specifying it as the operand of the [[00573.htm|Indirection ([] Operator)]]before the expression can be converted to an ''Indexed- ExpressionType''.''''''
 
When calculating a 16-bit effective address, only the '''BP'''and '''BX'''registers may be used as ''Base-Registers'', and only the '''DI'''and '''SI'''registers may be used as ''Index-Registers''.
 
When calculating a 32-bit effective address, only the '''EAX, EBX, ECX, EDX, EDI, ESI, EBP, and ESP'''registers may be used as ''Base-Registers'', and only the '''EAX, EBX, ECX, EDX, EDI, ESI, and EBP'''registers may be used as ''Index- Registers''.
 
'''Note:'''Only a single ''Base-Register''and a single ''Index-Register''may be used in a given expression.
 
 
 
On 80386 (and higher) processors, the [[00377.htm|Multiplication (* Operator)]]may be used with an ''Index-Register''operand and an [[00599.htm|''Absolute-ExpressionType'']]operand to establish a scaling factor that is applied to the ''Index-Register''during effective address calculation. The scaling factor effectively causes the ''Index-Register''to be multiplied by a fixed value at run time. The scaling [[00255.htm|''Expression'']]must evaluate to 1 (no scale factor), 2, 4, or 8.
 
A [[00602.htm|''Direct-ExpressionType'']]or an [[00603.htm|''Indirect-ExpressionType'']]may be a sub- expression of an ''Indexed-ExpressionType''.
 
[[[00604.htm|prev]]][[[00606.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Register Expression Type ===
 
A ''Register-ExpressionType''is an expression that specifies a single [[00122.htm|''Processor-Register'']].
 
[[[00605.htm|prev]]][[[00607.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== String Expression Type ===
 
A ''String-ExpressionType''is an expression that specifies a single [[00241.htm|''String- Literal'']].
 
[[[00606.htm|prev]]][[[00608.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Floating-Point Expression Type ===
 
A ''Floating-Point-ExpressionType''is an expression that specifies a single [[00226.htm|''Floating-Point-Literal'']].
 
[[[00607.htm|prev]]][[[00609.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Expression Type ===
 
A ''Type-ExpressionType''is an expression that specifies one of the following:
 
�A [[00125.htm|''Scalar-TypeName'']] <br />�A [[00128.htm|''Distance-TypeName'']] <br />�A [[00171.htm|''UserDefined-TypeName'']] <br />
 
[[[00608.htm|prev]]][[[00610.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Compound Expression Type ===
 
A ''Compound-ExpressionType''evaluates to a list of (possibly nested) expressions collected together as a unit by the [[00579.htm|Compound Initializer List ( &lt;&gt; Operator)]]. A ''Compound-ExpressionType''is used to initialize [[00711.htm|aggregate]] data types (such as records, structures, and unions) and [[00712.htm|vector]]data types (arrays).
 
[[[00609.htm|prev]]][[[00611.htm|next]]][[[00596.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Duplicated Expression Type ===
 
A ''Duplicated-ExpressionType''evaluates to an expression that is to be duplicated (repeated) a specified number of times. This type of expression is created using the [[00261.htm|Duplicative Initialization (DUP Operator)]].
 
[[[00610.htm|prev]]][[[00612.htm|next]]][[[00584.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operand Expression Type ===
 
 
-----
 
An ''Operand-ExpressionType''consists of those [[00596.htm|''ExpressionType'']]''s''that are valid for use as operands in processor instructions. The following [[00596.htm|''ExpressionType'']]''s''are not valid for use as an ''Operand-ExpressionType'''':''
 
�[[00609.htm|''Compound-ExpressionType'']] <br />�[[00610.htm|''Duplicated-ExpressionType'']] <br />
 
A [[00606.htm|''String-ExpressionType'']]is only valid as an ''Operand-ExpressionType''if it is short enough to be converted to an [[00599.htm|''Absolute-ExpressionType'']]having an [[00587.htm|''Operand Size'']]less than or equal to the current [[00586.htm|''Address Size'']]setting.
 
 
-----
 
''Operand-ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00604.htm|''Indexed-ExpressionType'']] <br />[[00605.htm|''Register-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br /> <br />
 
[[[00611.htm|prev]]][[[00613.htm|next]]][[[00611.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
An ''Operand-ExpressionType''consists of those [[00596.htm|''ExpressionType'']]''s''that are valid for use as operands in processor instructions. The following [[00596.htm|''ExpressionType'']]''s''are not valid for use as an ''Operand-ExpressionType'''':''
 
�[[00609.htm|''Compound-ExpressionType'']] <br />�[[00610.htm|''Duplicated-ExpressionType'']] <br />
 
A [[00606.htm|''String-ExpressionType'']]is only valid as an ''Operand-ExpressionType''if it is short enough to be converted to an [[00599.htm|''Absolute-ExpressionType'']]having an [[00587.htm|''Operand Size'']]less than or equal to the current [[00586.htm|''Address Size'']]setting.
 
[[[00612.htm|prev]]][[[00614.htm|next]]][[[00611.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Definition ===
 
''Operand-ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00604.htm|''Indexed-ExpressionType'']] <br />[[00605.htm|''Register-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br /> <br />
 
[[[00613.htm|prev]]][[[00615.htm|next]]][[[00584.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Initializer Expression Type ===
 
 
-----
 
An ''Initializer-ExpressionType''consists of those [[00596.htm|''ExpressionType'']]''s''that are valid for use in initializing variables. The following [[00596.htm|''ExpressionType'']]''s''are not valid ''Initializer-ExpressionType''''s'''':''
 
�[[00604.htm|''Indexed-ExpressionType'']] <br />�[[00605.htm|''Register-ExpressionType'']] <br />
 
 
-----
 
''Initializer-ExpressionType'''':'' <br />''Scalar-Initializer-ExpressionType'' <br />[[00609.htm|''Compound-ExpressionType'']] <br />[[00610.htm|''Duplicated-ExpressionType'']] <br /> <br />
 
''Scalar-Initializer-ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br /> <br />
 
[[[00614.htm|prev]]][[[00616.htm|next]]][[[00614.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
An ''Initializer-ExpressionType''consists of those [[00596.htm|''ExpressionType'']]''s''that are valid for use in initializing variables. The following [[00596.htm|''ExpressionType'']]''s''are not valid ''Initializer-ExpressionType''''s'''':''
 
�[[00604.htm|''Indexed-ExpressionType'']] <br />�[[00605.htm|''Register-ExpressionType'']] <br />
 
[[[00615.htm|prev]]][[[00617.htm|next]]][[[00614.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Definition ===
 
''Initializer-ExpressionType'''':'' <br />''Scalar-Initializer-ExpressionType'' <br />[[00609.htm|''Compound-ExpressionType'']] <br />[[00610.htm|''Duplicated-ExpressionType'']] <br /> <br />
 
''Scalar-Initializer-ExpressionType'''':'' <br />[[00599.htm|''Absolute-ExpressionType'']] <br />[[00600.htm|''Constant-ExpressionType'']] <br />[[00601.htm|''Immediate-ExpressionType'']] <br />[[00602.htm|''Direct-ExpressionType'']] <br />[[00603.htm|''Indirect-ExpressionType'']] <br />[[00606.htm|''String-ExpressionType'']] <br />[[00607.htm|''Floating-Point-ExpressionType'']] <br />[[00608.htm|''Type-ExpressionType'']] <br /> <br />
 
[[[00616.htm|prev]]][[[00618.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Preprocessor ===
 
The text preprocessor is a functional unit within the assembler that performs the '''''text preprocessing''translation phase. During text preprocessing, the following actions are performed:'''
 
1.[[00107.htm|Language Elements]]are recognized.
 
2.Text equates and macros are expanded.
 
3.[[00687.htm|Macro directives]]and [[00665.htm|conditional assembly directives]]are recognized and processed.
 
4.The preprocessed output is passed on to the assembler for final processing. <br />
 
 
 
This section also describes the various types of preprocessor directives: <br />
 
<pre>/-----------------------------------------------------------------------------\
|Type                    |Function                |Directives              |
|-------------------------+-------------------------+-------------------------|
|Conditional Assembly    |Tests for a specified    |IF                      |
|                        |condition and assembles a|IFB                      |
|                        |block of statements if  |IFDEF                    |
|                        |the condition is true.  |IFDIFI                  |
|                        |                        |IFE                      |
|                        |                        |IFIDN                    |
|                        |                        |IFNB                    |
|                        |                        |IFNDEF                  |
|                        |                        |IF1                      |
|                        |                        |IF2                      |
|                        |                        |ELSE                    |
|                        |                        |ENDIF                    |
|-------------------------+-------------------------+-------------------------|
|Text Equate              |Allows assignment of    |CATSTR                  |
|                        |simple text strings to a |EQU                      |
|                        |symbolic name. Provides  |INSTR                    |
|                        |functions for expanding  |SIZESTR                  |
|                        |and operating on the    |SUBSTR                  |
|                        |values.                  |                        |
|-------------------------+-------------------------+-------------------------|
|Macro                    |Provides text processing |ENDM                    |
|                        |that is done sequentially|EXITM                    |
|                        |at assembly time. By the |FOR                      |
|                        |end of assembly, ALP    |FORC                    |
|                        |expands all macros and  |IRP                      |
|                        |assembles the resulting  |IRPC                    |
|                        |text into object code.  |LOCAL                    |
|                        |                        |MACRO                    |
|                        |                        |PURGE                    |
|                        |                        |REPEAT                  |
|                        |                        |REPT                    |
|-------------------------+-------------------------+-------------------------|
|Miscellaneous            |Miscellaneous text      |COMMENT                  |
|                        |processing functions.    |ECHO                    |
|                        |                        |%OUT                    |
|                        |                        |INCLUDE                  |
\-----------------------------------------------------------------------------/</pre>
[[[00617.htm|prev]]][[[00619.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Operators ===
 
 
-----
 
The [[00617.htm|Text Preprocessor]]recognizes certain punctuator characters as text operators. The programmer may use these operators to force the [[00617.htm|Text Preprocessor]]to perform various operations such as delineating text, expanding arguments, and converting expressions into their text representations.
 
 
-----
 
''Text-Operator'''':'' <br />[[00621.htm|''Literal-Character-Operator'']] <br />[[00627.htm|''Literal-Text-Operator'']] <br />[[00632.htm|''Text-Expansion-Operator'']] <br />[[00638.htm|''Text-Substitution-Operator'']] <br /> <br />
 
[[[00618.htm|prev]]][[[00620.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The [[00617.htm|Text Preprocessor]]recognizes certain punctuator characters as text operators. The programmer may use these operators to force the [[00617.htm|Text Preprocessor]]to perform various operations such as delineating text, expanding arguments, and converting expressions into their text representations.
 
[[[00619.htm|prev]]][[[00621.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Text-Operator'''':'' <br />[[00621.htm|''Literal-Character-Operator'']] <br />[[00627.htm|''Literal-Text-Operator'']] <br />[[00632.htm|''Text-Expansion-Operator'']] <br />[[00638.htm|''Text-Substitution-Operator'']] <br /> <br />
 
[[[00620.htm|prev]]][[[00622.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Literal Character Operator (!) ===
 
 
-----
 
[[00624.htm|Description]]
 
[[00625.htm|Constraints]]
 
[[00626.htm|Examples]]
 
 
-----
 
When you use an exclamation point (!) in an operand, ALP treats the next character literally. (!) is typically used to prevent the assembler from recognizing and acting upon special characters such as the semicolon (;) or the ampersand (&amp;), forcing them to appear as normal data characters.
 
 
-----
 
''Literal-Character-Operator'''':'' <br />'''!'''any printable character <br /> <br />
 
[[[00621.htm|prev]]][[[00623.htm|next]]][[[00621.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00624.htm|Description]]
 
[[00625.htm|Constraints]]
 
[[00626.htm|Examples]]
 
[[[00622.htm|prev]]][[[00624.htm|next]]][[[00621.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Literal-Character-Operator'''':'' <br />'''!'''any printable character <br /> <br />
 
[[[00623.htm|prev]]][[[00625.htm|next]]][[[00621.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
When you use an exclamation point (!) in an operand, ALP treats the next character literally. (!) is typically used to prevent the assembler from recognizing and acting upon special characters such as the semicolon (;) or the ampersand (&amp;), forcing them to appear as normal data characters.
 
[[[00624.htm|prev]]][[[00626.htm|next]]][[[00621.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The ''Literal-Character-Operator''has no effect when used inside of a [[00241.htm|''String- Literal'']].
 
[[[00625.htm|prev]]][[[00627.htm|next]]][[[00621.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
In this example, use of the ! in the second macro argument prevents the assembler from interpreting the rest of the line as a comment: <br />
 
<pre>  MACRONAME  First ,  ! ; NonComment ,  Third              ; Comment </pre>
[[[00626.htm|prev]]][[[00628.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Literal Text Operator (&lt;&gt;) ===
 
 
-----
 
[[00630.htm|Description]]
 
[[00631.htm|Examples]]
 
 
-----
 
The literal-text operator directs the assembler to treat ''Char-Sequence''as a single literal element regardless of whether it contains commas, spaces, or other separators. The operator is most often used with macro calls and the FOR directive to ensure that values in a parameter list are treated as a single parameter.
 
The literal-text operator can also be used to force ALP to treat other special characters such as the semicolon (;) or the ampersand (&amp;) literally . For example, the semicolon inside angle brackets (&lt;;&gt;) becomes a semicolon, not a comment indicator.
 
ALP removes one set of angle brackets each time the parameter is used in a macro. When using nested macros, you will need to supply as many sets of angle brackets as there are levels of nesting. The assembler recognizes nested occurrences of text literals.
 
 
-----
 
''Literal-Text-Operator'''':'' <br />'''&lt;'''''Char-Sequence'''''&gt;''' <br /> <br />''Char-Sequence'' <br />any printable character <br />''Char-Sequence''any printable character <br /> <br />
 
[[[00627.htm|prev]]][[[00629.htm|next]]][[[00627.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00630.htm|Description]]
 
[[00631.htm|Examples]]
 
[[[00628.htm|prev]]][[[00630.htm|next]]][[[00627.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Literal-Text-Operator'''':'' <br />'''&lt;'''''Char-Sequence'''''&gt;''' <br /> <br />''Char-Sequence'' <br />any printable character <br />''Char-Sequence''any printable character <br /> <br />
 
[[[00629.htm|prev]]][[[00631.htm|next]]][[[00627.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The literal-text operator directs the assembler to treat ''Char-Sequence''as a single literal element regardless of whether it contains commas, spaces, or other separators. The operator is most often used with macro calls and the FOR directive to ensure that values in a parameter list are treated as a single parameter.
 
The literal-text operator can also be used to force ALP to treat other special characters such as the semicolon (;) or the ampersand (&amp;) literally . For example, the semicolon inside angle brackets (&lt;;&gt;) becomes a semicolon, not a comment indicator.
 
ALP removes one set of angle brackets each time the parameter is used in a macro. When using nested macros, you will need to supply as many sets of angle brackets as there are levels of nesting. The assembler recognizes nested occurrences of text literals.
 
[[[00630.htm|prev]]][[[00632.htm|next]]][[[00627.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following example illustrates how to pass arbitrary text to a macro as a single parameter: <br />
 
<pre>  MACRONAME  First ,  &lt; Second  Argument &gt; ,  &lt; Third ,  &lt; Nested &gt; ,  Argument &gt; </pre>
The macro will receive three separate arguments:
 
1.First <br /> 2.Second Argument <br /> 3.Third, &lt;Nested&gt;, Argument <br />
 
Notice that the outermost set of angle brackets were removed from the second and third arguments.
 
[[[00631.htm|prev]]][[[00633.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Expansion Operator (%) ===
 
 
-----
 
[[00635.htm|Description]]
 
[[00636.htm|Constraints]]
 
[[00637.htm|Examples]]
 
 
-----
 
The '''%'''''Text-Expansion-Operator''has different effects depending upon the context in which it is used. Its primary purpose is convert various sources of information into text literals that may in turn be passed to macros as arguments.
 
The '''%'''''Text-Expansion-Operator''causes the following types of conversions:
 
'''Line Expansion'''
 
When used as the first token on the line, the '''%'''operator forces expansion of [[00157.htm|''Text-EquateName'']]''s''in contexts where they would otherwise be left unexpanded. [[00157.htm|''Text-EquateName'']]''s''passed as arguments to macros are not automatically expanded; this is one context where the '''%'''operator is useful.
 
'''Expansion of a Text Equate Operand'''
 
As with '''''Line Expansion'', the '''%'''operator may be used within the body of a line to expand individual [[00157.htm|''Text-EquateName'']]''s''. This can be useful when expansion of all [[00157.htm|''Text-EquateName'']]''s''on the line is not desired.'''
 
'''Conversion of Numeric Expression to Text'''
 
If the ''Text-Expansion-Operator''is not the first token on the line or immediately followed by a [[00157.htm|''Text-EquateName'']], then the argument of the '''%''' operator is assumed to be an [[00255.htm|''Expression'']], which is evaluated and converted to the text representation of its value. This is useful when the need arises to pass the text representation of a number to a macro. <br />
 
 
-----
 
''Text-Expansion-Operator'''':'' <br />'''%'''2nd through Nth token on line <br />'''%'''[[00157.htm|''Text-EquateName'']] <br />'''%'''[[00255.htm|''Expression'']] <br /> <br />
 
[[[00632.htm|prev]]][[[00634.htm|next]]][[[00632.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00635.htm|Description]]
 
[[00636.htm|Constraints]]
 
[[00637.htm|Examples]]
 
[[[00633.htm|prev]]][[[00635.htm|next]]][[[00632.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Text-Expansion-Operator'''':'' <br />'''%'''2nd through Nth token on line <br />'''%'''[[00157.htm|''Text-EquateName'']] <br />'''%'''[[00255.htm|''Expression'']] <br /> <br />
 
[[[00634.htm|prev]]][[[00636.htm|next]]][[[00632.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The '''%'''''Text-Expansion-Operator''has different effects depending upon the context in which it is used. Its primary purpose is convert various sources of information into text literals that may in turn be passed to macros as arguments.
 
The '''%'''''Text-Expansion-Operator''causes the following types of conversions:
 
'''Line Expansion'''
 
When used as the first token on the line, the '''%'''operator forces expansion of [[00157.htm|''Text-EquateName'']]''s''in contexts where they would otherwise be left unexpanded. [[00157.htm|''Text-EquateName'']]''s''passed as arguments to macros are not automatically expanded; this is one context where the '''%'''operator is useful.
 
'''Expansion of a Text Equate Operand'''
 
As with '''''Line Expansion'', the '''%'''operator may be used within the body of a line to expand individual [[00157.htm|''Text-EquateName'']]''s''. This can be useful when expansion of all [[00157.htm|''Text-EquateName'']]''s''on the line is not desired.'''
 
'''Conversion of Numeric Expression to Text'''
 
If the ''Text-Expansion-Operator''is not the first token on the line or immediately followed by a [[00157.htm|''Text-EquateName'']], then the argument of the '''%''' operator is assumed to be an [[00255.htm|''Expression'']], which is evaluated and converted to the text representation of its value. This is useful when the need arises to pass the text representation of a number to a macro. <br />
 
[[[00635.htm|prev]]][[[00637.htm|next]]][[[00632.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
When the '''%'''[[00255.htm|''Expression'']]form of the expansion operator is used, the [[00255.htm|''Expression'']]must evaluate to an [[00601.htm|''Immediate-ExpressionType'']].
 
[[[00636.htm|prev]]][[[00638.htm|next]]][[[00632.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>MakErr      MACRO      X
LB          =          0
            REPEAT      X
LB          =          LB + 1
            MakLib      % LB
            ENDM        ; ; End  of  REPEAT
            ENDM        ; ; End  of  MACRO
MakLib      MACRO      Y
Err &amp; Y :    DB    ' Error    &amp; Y ' , 0
            ENDM
 
            MakErr  3
Err1 :    DB    ' Error  1 ' , 0
Err2 :    DB    ' Error  2 ' , 0
Err3 :    DB    ' Error  3 ' , 0 </pre>
[[[00637.htm|prev]]][[[00639.htm|next]]][[[00618.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Substitution Operator (&amp;) ===
 
 
-----
 
[[00641.htm|Description]]
 
[[00642.htm|Constraints]]
 
[[00643.htm|Examples]]
 
 
-----
 
An ampersand (&amp;) is used in the body of a macro to force the substitution of a [[00169.htm|''Macro-ParameterName'']]with the value of its argument during expansion of the macro.
 
 
-----
 
''Text-Substitution-Operator'''':'' <br />[[00169.htm|''Macro-ParameterName'']]'''&amp;''' <br />'''&amp;'''[[00169.htm|''Macro-ParameterName'']] <br /> <br />
 
[[[00638.htm|prev]]][[[00640.htm|next]]][[[00638.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00641.htm|Description]]
 
[[00642.htm|Constraints]]
 
[[00643.htm|Examples]]
 
[[[00639.htm|prev]]][[[00641.htm|next]]][[[00638.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Text-Substitution-Operator'''':'' <br />[[00169.htm|''Macro-ParameterName'']]'''&amp;''' <br />'''&amp;'''[[00169.htm|''Macro-ParameterName'']] <br /> <br />
 
[[[00640.htm|prev]]][[[00642.htm|next]]][[[00638.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
An ampersand (&amp;) is used in the body of a macro to force the substitution of a [[00169.htm|''Macro-ParameterName'']]with the value of its argument during expansion of the macro.
 
[[[00641.htm|prev]]][[[00643.htm|next]]][[[00638.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
The assembler does not substitute a [[00169.htm|''Macro-ParameterName'']]that is in a quoted string or not preceded by a delimiter in the expansion unless it is immediately preceded by an ampersand (&amp;).
 
It is necessary to separate a [[00169.htm|''Macro-ParameterName'']]from other [[00149.htm|''Identifer- Character'']]''s''with an ampersand (&amp;) before any substitution or paste operations are performed.
 
[[[00642.htm|prev]]][[[00644.htm|next]]][[[00638.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>ErrGen      MACRO      X
Error &amp; X :    push      bx
ABX        mov        BX ,  &quot; A &quot;
AB &amp; X        jmp        ERROR
          ENDM </pre>
The statement '''ErrGen A'''produces this code: <br />
 
<pre>ErrorA :    push      bx
ABX        mov        BX ,  &quot; A &quot;
ABA        jmp        ERROR </pre>
[[[00643.htm|prev]]][[[00645.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Preprocessor Tokens ===
 
 
-----
 
During the text preprocessing translation phase, certain conditions will cause the preprocessor to convert raw [[00107.htm|Language Elements]]([[00107.htm|''Token'']]''s'') into ''Preprocessing-Token''''s''. The act of text preprocessing typically causes ''Preprocessing-Token''''s''to either be removed from the input stream or converted back into [[00107.htm|''Token'']]''s''before being passed on to the assembler for final processing.
 
 
 
 
-----
 
''Preprocessing-Token'''':'' <br />[[00149.htm|''Identifier'']] <br />[[00647.htm|''Text-Literal'']] <br />[[00652.htm|''FileName'']] <br />[[00657.htm|''Comment'']] <br /> <br />
 
[[[00644.htm|prev]]][[[00646.htm|next]]][[[00644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
During the text preprocessing translation phase, certain conditions will cause the preprocessor to convert raw [[00107.htm|Language Elements]]([[00107.htm|''Token'']]''s'') into ''Preprocessing-Token''''s''. The act of text preprocessing typically causes ''Preprocessing-Token''''s''to either be removed from the input stream or converted back into [[00107.htm|''Token'']]''s''before being passed on to the assembler for final processing.
 
[[[00645.htm|prev]]][[[00647.htm|next]]][[[00644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Preprocessing-Token'''':'' <br />[[00149.htm|''Identifier'']] <br />[[00647.htm|''Text-Literal'']] <br />[[00652.htm|''FileName'']] <br />[[00657.htm|''Comment'']] <br /> <br />
 
[[[00646.htm|prev]]][[[00648.htm|next]]][[[00644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Literals ===
 
 
-----
 
[[00650.htm|Description]]
 
[[00651.htm|Constraints]]
 
 
-----
 
A ''Text-Literal''is a single unit of text that is used by the [[00617.htm|Text Preprocessor]]in many different text handling contexts. In some contexts ( such as the processing of arguments to be passed to a macro), normal language [[00107.htm|''Token'']]''s''are implicitly treated as ''Text-Literal''''s'', provided they are not a delimiter character such as a comma or a blank. In other contexts, it may be necessary to explicitly convert a unit of text to a ''Text-Literal'' using the [[00627.htm|''Literal-Text-Operator'']].
 
 
-----
 
''Text-Literal'''':'' <br />operand of [[00621.htm|''Literal-Character-Operator'']] <br />operand of [[00627.htm|''Literal-Text-Operator'']] <br /> <br />
 
[[[00647.htm|prev]]][[[00649.htm|next]]][[[00647.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00650.htm|Description]]
 
[[00651.htm|Constraints]]
 
[[[00648.htm|prev]]][[[00650.htm|next]]][[[00647.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Text-Literal'''':'' <br />operand of [[00621.htm|''Literal-Character-Operator'']] <br />operand of [[00627.htm|''Literal-Text-Operator'']] <br /> <br />
 
[[[00649.htm|prev]]][[[00651.htm|next]]][[[00647.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
A ''Text-Literal''is a single unit of text that is used by the [[00617.htm|Text Preprocessor]]in many different text handling contexts. In some contexts ( such as the processing of arguments to be passed to a macro), normal language [[00107.htm|''Token'']]''s''are implicitly treated as ''Text-Literal''''s'', provided they are not a delimiter character such as a comma or a blank. In other contexts, it may be necessary to explicitly convert a unit of text to a ''Text-Literal'' using the [[00627.htm|''Literal-Text-Operator'']].
 
[[[00650.htm|prev]]][[[00652.htm|next]]][[[00647.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Constraints ===
 
A normal language [[00107.htm|''Token'']]is never implicitly considered to be a ''Text-Literal'' if a ''Text-Literal''is explicitly required in the syntax of the construct being parsed.
 
[[[00651.htm|prev]]][[[00653.htm|next]]][[[00644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== File Names ===
 
 
-----
 
[[00655.htm|Description]]
 
[[00656.htm|Examples]]
 
 
-----
 
''FileName''arguments may be coded as an arbitrary sequence of printable characters, or as a [[00647.htm|''Text-Literal'']]; use the [[00647.htm|''Text-Literal'']]form if the ''FileName'' is to contain embedded spaces or other special characters.
 
If path information is included in the ''FileName'', you can separate the individual directory names with either the back slash (\) or the forward slash (/) and they will be treated identically by the assembler.
 
 
-----
 
''FileName'''':'' <br />''FileName-Text'' <br />[[00647.htm|''Text-Literal'']] <br /> <br />''FileName-Text'''':'' <br />''FileName-Character'' <br />''FileName-Text''''FileName-Character'' <br /> <br />''FileName-Character''.'':'' <br />any printable character except blank (ASCII 32) <br /> <br />
 
[[[00652.htm|prev]]][[[00654.htm|next]]][[[00652.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00655.htm|Description]]
 
[[00656.htm|Examples]]
 
[[[00653.htm|prev]]][[[00655.htm|next]]][[[00652.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''FileName'''':'' <br />''FileName-Text'' <br />[[00647.htm|''Text-Literal'']] <br /> <br />''FileName-Text'''':'' <br />''FileName-Character'' <br />''FileName-Text''''FileName-Character'' <br /> <br />''FileName-Character''.'':'' <br />any printable character except blank (ASCII 32) <br /> <br />
 
[[[00654.htm|prev]]][[[00656.htm|next]]][[[00652.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
''FileName''arguments may be coded as an arbitrary sequence of printable characters, or as a [[00647.htm|''Text-Literal'']]; use the [[00647.htm|''Text-Literal'']]form if the ''FileName'' is to contain embedded spaces or other special characters.
 
If path information is included in the ''FileName'', you can separate the individual directory names with either the back slash (\) or the forward slash (/) and they will be treated identically by the assembler.
 
[[[00655.htm|prev]]][[[00657.htm|next]]][[[00652.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
<br />
 
<pre>  INCLUDE      &lt; inc \ macros . inc &gt;
  INCLUDELIB  os2386 . lib </pre>
[[[00656.htm|prev]]][[[00658.htm|next]]][[[00644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Comments ===
 
 
-----
 
[[00660.htm|Description]]
 
[[00661.htm|Examples]]
 
 
-----
 
'''''Comments''are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.'''
 
There are two classes of comments recognized by ALP:
 
�Comments that start with a character sequence and continue to the end of the line (''EndOfLine-Comment'')
 
�Comments that start with a character sequence and continue until the occurrence of another character sequence (''Block-Comment''). See the [[00700.htm|COMMENT]] directive for a description of [[00700.htm|''Block-Comment'']]''s''. <br />
 
 
 
There are two types of ''EndOfLine-Comment''''s'''':''
 
'''''Macro-Comment'''''
 
'''''Macro-Comments''(beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of ''Macro-Comments''can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, ''Macro-Comments''are discarded and not entered into the macro definition, whereas ''NonMacro-Comments''are treated as normal text and are retained.'''
 
'''''NonMacro-Comment'''''
 
'''''NonMacro-Comment''(beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions. <br />'''
 
 
-----
 
''Comment'''':'' <br />''EndOfLine-Comment'' <br />[[00700.htm|''Block-Comment'']] <br /> <br />''EndOfLine-Comment'''':'' <br />''NonMacro-Comment'' <br />''Macro-Comment'' <br /> <br />''NonMacro-Comment'''':'' <br />''';'''''Char-Sequence'' <br /> <br />''Macro-Comment'''':'' <br />''';;'''''Char-Sequence'' <br /> <br />''Char-Sequence'''':'' <br />any printable character <br />''Char-Sequence''any printable character <br /> <br />[[00700.htm|''Block-Comment'']]'':'' <br />See the [[00700.htm|COMMENT]]directive <br /> <br />
 
[[[00657.htm|prev]]][[[00659.htm|next]]][[[00657.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[00660.htm|Description]]
 
[[00661.htm|Examples]]
 
[[[00658.htm|prev]]][[[00660.htm|next]]][[[00657.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Comment'''':'' <br />''EndOfLine-Comment'' <br />[[00700.htm|''Block-Comment'']] <br /> <br />''EndOfLine-Comment'''':'' <br />''NonMacro-Comment'' <br />''Macro-Comment'' <br /> <br />''NonMacro-Comment'''':'' <br />''';'''''Char-Sequence'' <br /> <br />''Macro-Comment'''':'' <br />''';;'''''Char-Sequence'' <br /> <br />''Char-Sequence'''':'' <br />any printable character <br />''Char-Sequence''any printable character <br /> <br />[[00700.htm|''Block-Comment'']]'':'' <br />See the [[00700.htm|COMMENT]]directive <br /> <br />
 
[[[00659.htm|prev]]][[[00661.htm|next]]][[[00657.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
'''''Comments''are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.'''
 
There are two classes of comments recognized by ALP:
 
�Comments that start with a character sequence and continue to the end of the line (''EndOfLine-Comment'')
 
�Comments that start with a character sequence and continue until the occurrence of another character sequence (''Block-Comment''). See the [[00700.htm|COMMENT]] directive for a description of [[00700.htm|''Block-Comment'']]''s''. <br />
 
 
 
There are two types of ''EndOfLine-Comment''''s'''':''
 
'''''Macro-Comment'''''
 
'''''Macro-Comments''(beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of ''Macro-Comments''can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, ''Macro-Comments''are discarded and not entered into the macro definition, whereas ''NonMacro-Comments''are treated as normal text and are retained.'''
 
'''''NonMacro-Comment'''''
 
''NonMacro-Comment''(beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions. <br />
 
[[[00660.htm|prev]]][[[00662.htm|next]]][[[00657.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Examples ===
 
The following are examples of ''EndOfLine-Comment''''s'''':''<br />
 
<pre>;  Comments  may  be  on  a  line  all  by  themselves .    They  can  be  empty . . .
;
                                ;  They  don ' t  have  to  start  in  the  first  column
BumpCount  MACRO  Amount        ;  They  can  appear  to  the  right  of  statements
  Count  =  Count  +  Amount      ;  This  appears  in  macro  expansions
  $ Total  =  $ Total  +  Amount    ; ; This  does  not ,  discarded  during  definition
ENDM </pre>
[[[00661.htm|prev]]][[[00663.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Arguments ===
 
 
-----
 
Many preprocessing directives operate on sequences of raw text characters called ''Text-Argument''''s''. A ''Text-Argument''may be specified using any one of several methods:
 
�Specifying the text directly using a raw [[00647.htm|''Text-Literal'']].
 
�Using the [[00632.htm|''Text-Expansion-Operator'']]to convert a numeric expression to its text representation.
 
�Using a [[00157.htm|''Text-EquateName'']]in those contexts where a ''Text-Argument''is expected. In this case the preprocessor will automatically resolve the [[00157.htm|''Text-EquateName'']]and use its value as the ''Text-Argument''. <br />
 
 
 
 
-----
 
''Text-Argument'''':'' <br />[[00647.htm|''Text-Literal'']] <br />'''%'''[[00255.htm|''Expression'']] <br />[[00157.htm|''Text-EquateName'']] <br /> <br />
 
[[[00662.htm|prev]]][[[00664.htm|next]]][[[00662.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Many preprocessing directives operate on sequences of raw text characters called ''Text-Argument''''s''. A ''Text-Argument''may be specified using any one of several methods:
 
�Specifying the text directly using a raw [[00647.htm|''Text-Literal'']].
 
�Using the [[00632.htm|''Text-Expansion-Operator'']]to convert a numeric expression to its text representation.
 
�Using a [[00157.htm|''Text-EquateName'']]in those contexts where a ''Text-Argument''is expected. In this case the preprocessor will automatically resolve the [[00157.htm|''Text-EquateName'']]and use its value as the ''Text-Argument''. <br />
 
[[[00663.htm|prev]]][[[00665.htm|next]]][[[00662.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Syntax ===
 
''Text-Argument'''':'' <br />[[00647.htm|''Text-Literal'']] <br />'''%'''[[00255.htm|''Expression'']] <br />[[00157.htm|''Text-EquateName'']] <br /> <br />
 
[[[00664.htm|prev]]][[[00666.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Conditional Assembly Directives ===
 
At assembly time, ALP evaluates conditional assembly directives, assembling if the conditions are true. You can use conditional assembly directives when you want to test for a specified condition and assemble a block of statements if the condition is true. The [[00666.htm|IFxx]]and [[00680.htm|ENDIF]]directives enclose the statements to be considered for conditional assembly. The optional [[00679.htm|ELSEIFxx]]and [[00679.htm|ELSE]]blocks follow the [[00666.htm|IFxx]]directive. There are many forms of the [[00666.htm|IFxx]]and [[00679.htm|ELSEIFxx]]directives.
 
This section describes the following conditional assembly directives:
 
[[00667.htm|IF]] <br />[[00668.htm|IFB]] <br />[[00669.htm|IFDEF]] <br />[[00670.htm|IFDIF]] <br />[[00671.htm|IFDIFI]] <br />[[00672.htm|IFE]] <br />[[00673.htm|IFIDN]] <br />[[00674.htm|IFIDNI]] <br />[[00675.htm|IFNB]] <br />[[00676.htm|IFNDEF]] <br />[[00677.htm|IF1]] <br />[[00678.htm|IF2]] <br />[[00679.htm|ELSE]] <br />[[00680.htm|ENDIF]] <br />
 
[[[00665.htm|prev]]][[[00667.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFxx (Begin Primary Conditional Block) ===
 
You can use each '''IFxx'''conditional directive with the [[00679.htm|ELSExx]], [[00679.htm|ELSE]]and [[00680.htm|ENDIF]] directives to provide the statements to be considered for conditional assembly. ALP assembles the statements following the [[00666.htm|IFxx]]directive only if this condition is true.
 
'''Syntax'''
 
<br />
 
<pre>IFxx  operand
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF </pre>
'''Remarks'''
 
The following directives are members of the '''IFxx'''family:
 
�[[00667.htm|IF]] <br />�[[00668.htm|IFB]] <br />�[[00669.htm|IFDEF]] <br />�[[00670.htm|IFDIF]] <br />�[[00671.htm|IFDIFI]] <br />�[[00672.htm|IFE]] <br />�[[00673.htm|IFIDN]] <br />�[[00674.htm|IFIDNI]] <br />�[[00675.htm|IFNB]] <br />�[[00676.htm|IFNDEF]] <br />�[[00677.htm|IF1]] <br />�[[00678.htm|IF2]]
 
You can nest the conditional directives to any level. They are not limited to use within a macro. The assembler must know any operand to a conditional on pass one to avoid errors and incorrect evaluation. <br />
 
[[[00666.htm|prev]]][[[00668.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IF (If Expression is True) ===
 
'''IF'''starts a conditional assembly statement, which is ended by the corresponding [[00680.htm|ENDIF]]conditional assembly directive. Each '''IF'''directive must be ended by a matching [[00680.htm|ENDIF]]directive.
 
'''Syntax'''
 
<br />
 
<pre>IF  Expression
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF </pre>
'''Remarks'''
 
If the [[00666.htm|IFxx]]conditional assembly statement is not ended by an [[00680.htm|ENDIF]] directive, an ''unterminated conditional''message is produced by the assembler . An [[00680.htm|ENDIF]]without a matching '''IF'''causes an error. [[00680.htm|ENDIF]]does not have an operand.
 
 
 
'''Note:'''The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.
 
'''Example'''
 
<br />
 
<pre>IF  debug
      EXTERN  dump : FAR
      EXTERN  trace : FAR
      EXTERN  breakpoint : FAR
ENDIF </pre>
<br />
 
[[[00667.htm|prev]]][[[00669.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFB (If Argument is Blank) ===
 
This is true if [[00662.htm|''Text-Argument'']]is blank (contains no characters).
 
'''Syntax'''
 
<br />
 
<pre>IFB  Text - Argument </pre>
'''Remarks'''
 
A [[00662.htm|''Text-Argument'']]must be specified, the contents of which are checked for the presence of characters. An error is generated if a [[00662.htm|''Text-Argument'']]is not supplied. <br />
 
[[[00668.htm|prev]]][[[00670.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFDEF (If Identifier is Defined) ===
 
This is true if [[00149.htm|''Identifier'']]has been defined as a label, variable, or symbol .
 
'''Syntax'''
 
<br />
 
<pre>IFDEF  Identifier </pre>
<br />
 
[[[00669.htm|prev]]][[[00671.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFDIF (If Arguments Are Different) ===
 
This is true if [[00662.htm|''Text-Argument'']]''-1''and [[00662.htm|''Text-Argument'']]''-2''are different in a case -sensitive comparison.
 
'''Syntax'''
 
<br />
 
<pre>IFDIF  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
Both [[00662.htm|''Text-Argument'']]arguments must be specified. An error is generated if a either argument is not supplied.
 
'''Example'''
 
In the following example: <br />
 
<pre>IFDIF  &lt; EAGLES &gt; , &lt; Eagles &gt;
  value  =  1
ENDIF </pre>
the condition would be true; the arguments are different because they are compared with a case-sensitive algorithm. <br />
 
[[[00670.htm|prev]]][[[00672.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFDIFI (If Arguments Are Spelled Differently) ===
 
This is true if [[00662.htm|''Text-Argument'']]''-1''and [[00662.htm|''Text-Argument'']]''-2''are different in a case -insensitive comparison.
 
'''Syntax'''
 
<br />
 
<pre>IFDIFI  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
Both [[00662.htm|''Text-Argument'']]arguments must be specified. An error is generated if a either argument is not supplied.
 
'''Example'''
 
In the following example: <br />
 
<pre>IFDIFI  &lt; EAGLES &gt; , &lt; Eagles &gt;
  value  =  1
ENDIF </pre>
the condition would be false; the arguments are not different because they are compared using a case-insensitive algorithm. <br />
 
[[[00671.htm|prev]]][[[00673.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFE (If Expression is Not True) ===
 
This is true if ''expression''is 0.
 
'''Syntax'''
 
<br />
 
<pre>IFE  Expression </pre>
<br />
 
[[[00672.htm|prev]]][[[00674.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFIDN (If Arguments Are Identical) ===
 
This is true if [[00662.htm|''Text-Argument'']]''-1''and [[00662.htm|''Text-Argument'']]''-2''are identical in a case -sensitive comparison.
 
'''Syntax'''
 
<br />
 
<pre>IFIDN  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
Both [[00662.htm|''Text-Argument'']]arguments must be specified. An error is generated if a either argument is not supplied.
 
'''Example'''
 
In the following example: <br />
 
<pre>IFIDN  &lt; EAGLES &gt; , &lt; Eagles &gt;
  value  =  1
ENDIF </pre>
the condition would be false; the arguments are not identical because they are compared using a case-insensitive algorithm. <br />
 
[[[00673.htm|prev]]][[[00675.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFIDNI (If Arguments Are Spelled Identically) ===
 
This is true if [[00662.htm|''Text-Argument'']]''-1''and [[00662.htm|''Text-Argument'']]''-2''are identical in a case -insensitive comparison.
 
'''Syntax'''
 
<br />
 
<pre>IFIDNI  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
Both [[00662.htm|''Text-Argument'']]arguments must be specified. An error is generated if a either argument is not supplied.
 
'''Example'''
 
In the following example: <br />
 
<pre>IFIDNI  &lt; EAGLES &gt; , &lt; Eagles &gt;
  value  =  1
ENDIF </pre>
the condition would be true; the arguments are identical because they are compared using a case-insensitive algorithm. <br />
 
[[[00674.htm|prev]]][[[00676.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFNB (If Argument is Not Blank) ===
 
This is true if [[00662.htm|''Text-Argument'']]is not blank (characters are present).
 
'''Syntax'''
 
<br />
 
<pre>IFNB  Text - Argument </pre>
'''Remarks'''
 
A [[00662.htm|''Text-Argument'']]must be specified, the contents of which are checked for the presence of characters. An error is generated if a [[00662.htm|''Text-Argument'']]is not supplied. <br />
 
[[[00675.htm|prev]]][[[00677.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IFNDEF (If Identifier is Not Defined) ===
 
This is true if ''symbol''has not yet been defined as a label, variable, or symbol.
 
'''Syntax'''
 
<br />
 
<pre>IFNDEF  symbol </pre>
<br />
 
[[[00676.htm|prev]]][[[00678.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IF1 (If Assembling On Pass 1) ===
 
This is true on pass one.
 
'''Syntax'''
 
<br />
 
<pre>IF1 </pre>
'''Remarks'''
 
'''IF1'''does not have an operand. <br />
 
[[[00677.htm|prev]]][[[00679.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== IF2 (If Assembling On Pass 2) ===
 
This is true on pass two.
 
'''Syntax'''
 
<br />
 
<pre>IF2 </pre>
'''Remarks'''
 
'''IF2'''does not have an operand. <br />
 
[[[00678.htm|prev]]][[[00680.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ELSEIFxx/ELSE (Begin Alternate Conditional Block) ===
 
Each conditional directive can be used with the '''ELSE'''directive to provide the statements to be considered for conditional assembly. The '''ELSE''' directive allows the assembly of the statements following it when the [[00666.htm|IFxx]] condition or intervening '''ELSEIFxx'''conditions are false.
 
'''Syntax'''
 
<br />
 
<pre>IFxx
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF </pre>
'''Remarks'''
 
There is a corresponding '''ELSEIFxx'''directive to match all forms of the [[00666.htm|IFxx]] family of directives:
 
�[[00667.htm|ELSEIF]] <br />�[[00668.htm|ELSEIFB]] <br />�[[00669.htm|ELSEIFDEF]] <br />�[[00670.htm|ELSEIFDIF]] <br />�[[00671.htm|ELSEIFDIFI]] <br />�[[00672.htm|ELSEIFE]] <br />�[[00673.htm|ELSEIFIDN]] <br />�[[00674.htm|ELSEIFIDNI]] <br />�[[00675.htm|ELSEIFNB]] <br />�[[00676.htm|ELSEIFNDEF]] <br />�[[00677.htm|ELSEIF1]] <br />�[[00678.htm|ELSEIF2]]
 
For information about the meaning of the conditional tests performed by the '''ELSEIFxx'''directives, refer to the definitions for the corresponding [[00666.htm|IFxx]] directives.
 
Any number of '''ELSEIFxx'''blocks may be used within a given [[00666.htm|IFxx]]statement. Only one '''ELSE'''block is permitted for a given [[00666.htm|IFxx]]. A conditional directive with more than one '''ELSE'''or an '''ELSE'''without a conditional directive causes an error. '''ELSE'''does not have an operand.
 
 
 
'''Note:'''The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.
 
'''Example'''
 
<br />
 
<pre>IF  DEFBUF
 
    BUF  DB  100  DUP ( 0 )
 
ELSE
 
    EXTERN  BUF : BYTE
 
ENDIF </pre>
<br />
 
[[[00679.htm|prev]]][[[00681.htm|next]]][[[00665.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ENDIF (End a Conditional Assembly Statement) ===
 
'''ENDIF'''ends the conditional assembly statement begun by the corresponding [[00666.htm|IFxx]]conditional assembly directive. Each [[00666.htm|IFxx]]directive must be ended by a matching '''ENDIF'''directive.
 
'''Syntax'''
 
<br />
 
<pre>IFxx
    .
    .
    .
[ ELSEIFxx ]  ( optional )
    .
    .
    .
[ ELSE ]  ( optional )
    .
    .
    .
ENDIF </pre>
'''Remarks'''
 
If the [[00666.htm|IFxx]]conditional assembly statement is not ended by an '''ENDIF''' directive, an '''unterminated conditional'''message is produced by the assembler . An '''ENDIF'''without a matching [[00666.htm|IFxx]]causes an error. '''ENDIF'''does not have an operand.
 
 
 
'''Note:'''The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.
 
'''Example'''
 
<br />
 
<pre>IF  debug
    EXTERN  dump : FAR
    EXTERN  trace : FAR
    EXTERN  breakpoint : FAR
ENDIF </pre>
<br />
 
[[[00680.htm|prev]]][[[00682.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Text Equate Directives ===
 
A '''''Text Equate''is a symbolic name you give to a series of characters. Text equates are used to expand text within a source statement. The directives described in this section create and manipulate text equates.'''
 
EQU <br />CATSTR <br />INSTR <br />SIZESTR <br />SUBSTR <br />
 
[[[00681.htm|prev]]][[[00683.htm|next]]][[[00681.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CATSTR (Concatenate Strings) ===
 
'''CATSTR'''concatenates a list of text values specified by ''string''into a single text value and assigns it to ''Name''.
 
'''Syntax'''
 
<br />
 
<pre>Name  CATSTR  string [ ,  string ]  . . . </pre>
<br />
 
[[[00682.htm|prev]]][[[00684.htm|next]]][[[00681.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EQU Directive (Assign Text to a Symbolic Constant) ===
 
The '''EQU'''directive assigns the contents of a text literal to ''Name''.
 
'''Syntax'''
 
<br />
 
<pre>Name  EQU  Text - Literal </pre>
'''Remarks'''
 
The value of the [[00647.htm|''Text-Literal'']]is assigned to the ''Name''entry. In normal contexts, subsequent references to ''Name''will cause the preprocessor to replace ''Name''with the value specified by the [[00647.htm|''Text-Literal'']]entry. This is a simple text substitution operation.
 
The ''Name''entry is a globally-scoped [[00149.htm|''Identifier'']]that is converted to a [[00157.htm|''Text- EquateName'']]. The ''Name''cannot have been previously defined as a different [[00152.htm|''Identifier-Type'']]. However, the ''Name''entry can be redefined as many times as desired with different values for the [[00647.htm|''Text-Literal'']]entry.
 
See also [[00791.htm|EQU]]and [[00786.htm|=]].
 
'''Example'''
 
<br />
 
<pre>A      EQU    &lt; BP  + &gt;    ; explicit  text  literal ,  A  is  a  text  equate
A      EQU    &lt; 3 &gt;      ; redefinition  of  A  with  different  value </pre>
<br />
 
[[[00683.htm|prev]]][[[00685.htm|next]]][[[00681.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== INSTR (Search In String For Value) ===
 
'''INSTR'''searches a specified ''String''for an occurrence of a given ''Sub-String'' and assigns its position (1-based) to ''Name''. The search is case sensitive. ''Start''is the position in ''String''to start the search for ''Sub-String''. If ''Start''is not given, it is assumed to be 1 (the start of the string). If ''Sub-String''is not found, the position assigned to ''Name''is 0.
 
'''Syntax'''
 
<br />
 
<pre>Name  INSTR  [ Start , ] String , Sub - String </pre>
'''Remarks'''
 
'''INSTR'''assigns the position value to a name as if it were a numeric equate.
 
'''Example'''
 
<br />
 
<pre>pos  INSTR  &lt; person &gt; ,  &lt; son &gt; </pre>
<br />
 
[[[00684.htm|prev]]][[[00686.htm|next]]][[[00681.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== SIZESTR (Return Size Of String) ===
 
Assigns the number of characters given by the [[00662.htm|''Text-Argument'']]to ''Name''.
 
'''Syntax'''
 
<br />
 
<pre>Name  SIZESTR  Text - Argument </pre>
<br />
 
[[[00685.htm|prev]]][[[00687.htm|next]]][[[00681.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== SUBSTR (Extract a Sub-string From a String) ===
 
Assigns a substring of [[00662.htm|''Text-Argument'']]starting at ''Position''to the symbol given by ''Name.''.
 
'''Syntax'''
 
<br />
 
<pre>Name  SUBSTR  Text - Argument , Position [ , Length ] </pre>
'''Remarks'''
 
The ''Position''parameter indicates the starting character of the substring to extract from the [[00662.htm|''Text-Argument'']], and must be 1 or greater. If specified, the ''Length''parameter indicates how many characters are desired, otherwise the remainder of the string is extracted. <br />
 
[[[00686.htm|prev]]][[[00688.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Macro Directives ===
 
'''A macro procedure or function''', which is comprised of one or more statements .
 
Macro processing is text processing that is done sequentially at assembly time. By the end of assembly, ALP expands all macros and assembles the resulting text into object code.
 
This section describes the following types of macros:
 
�Macro procedures, which expand to one or more complete statements and can optionally take parameters <br />�Repeat blocks, which generate a group of statements a specified number of times or until a condition becomes true <br />
 
This section describes the following macro directives:
 
ENDM <br />EXITM <br />FOR/IRP <br />FORC/IRPC <br />LOCAL <br />MACRO <br />PURGE <br />REPEAT/REPT <br />
 
[[[00687.htm|prev]]][[[00689.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ENDM (End Current Macro Definition) ===
 
End each [[00693.htm|MACRO]], [[00697.htm|REPEAT/REPT]], [[00690.htm|FOR/IRP]], and [[00691.htm|FORC/IRPC]]directive with the '''ENDM''' directive.
 
'''Syntax'''
 
<br />
 
<pre>ENDM </pre>
'''Remarks'''
 
If the '''ENDM'''directive is not used with the [[00693.htm|MACRO]], [[00697.htm|REPEAT/REPT]], [[00690.htm|FOR/IRP]], and [[00691.htm|FORC/IRPC]]directives, an error occurs. An unmatched '''ENDM'''also causes an error.
 
If the assembler produces an error message stating that it found the end-of -file on the source and cannot find an [[00715.htm|END]]statement when there was an [[00715.htm|END]], the likely cause is a missing '''ENDM'''or ENDIF statement. Without '''ENDM''', the assembler treats the rest of the source as part of the [[00693.htm|MACRO]]definition.
 
'''Note:'''The ''name field''is not allowed. Do not confuse the '''ENDM'''directive with other ending directives that do require the name of the block being ended, such as ENDP or ENDS.
 
'''Example'''
 
<br />
 
<pre>addup    MACRO    ad1 , ad2 , ad3
        MOV      AX , ad1        ; ; first  parameter  in  AX
        ADD      AX , ad2        ; ; add  next  two  parameters
        ADD      AX , ad3        ; ; leave  sum  in  AX
        ENDM </pre>
<br />
 
[[[00688.htm|prev]]][[[00690.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EXITM (End Current Macro Expansion) ===
 
Use the '''EXITM'''directive when a block contains a directive that tests for some condition and you want to end the current macro expansion when the test proves that the remainder of the expansion is not required. When an '''EXITM'''directive is run, the expansion is stopped immediately, and any remaining expansion or repetition is not produced.
 
'''Syntax'''
 
<br />
 
<pre>EXITM </pre>
'''Remarks'''
 
Only the block containing the '''EXITM'''directive is ended; outer levels of a nested macro expansion continue unaffected.
 
'''EXITM'''is executed at macro expansion time and is not a substitute for the [[00688.htm|ENDM]]directive, which marks the end of the macro body and is recognized at macro definition time.
 
'''Example'''
 
<br />
 
<pre>DSEG  SEGMENT
      .
      .
      .
SYM  =  0
      REPEAT  16
; ; Check  for  paragraph  boundary
      IF  ( $ - DSEG )  MOD  16  EQ  0
      EXITM  ; ; quit  if  padded  to  boundary
      ENDIF
SYM  =  SYM  +  1
      DB  SYM  ; ; produce  numbered  padding
      ENDM </pre>
<br />
 
[[[00689.htm|prev]]][[[00691.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FOR/IRP (Iterative Macro Expansion Using List of Arguments) ===
 
The '''FOR'''directive, used in combination with the [[00688.htm|ENDM]]directive, designates a block of statements to be repeated, once for each argument in the list enclosed by angle brackets. Each repetition substitutes the next item in the &lt;''Argument-List''&gt; entry for every occurrence of ''Parameter''in the block.
 
'''Syntax'''
 
<br />
 
<pre>FOR  Parameter ,  &lt; Argument - List &gt;
    .
    .
    .
ENDM </pre>
'''Remarks'''
 
The obsolete spelling for the '''FOR'''directive is '''IRP'''.
 
You must enclose the &lt;''Argument-List''&gt; entry in angle brackets. It has the following format: <br />
 
<pre>&lt; [ Argument  [ ,  Argument  . . . ] ] &gt; </pre>
If an empty (&lt;&gt;) ''Argument''is found in &lt;''Argument-List''&gt;, the ''Parameter''name is replaced by a null value. If the argument list is empty, the '''FOR''' directive is ignored and no statements are copied. The assembler processes the block once for each ''Argument''in the &lt;''Argument-List''&gt;, replacing each occurrence of ''Parameter''in the macro body with the current ''Argument''value.
 
The [[00690.htm|FOR/IRP]]-[[00688.htm|ENDM]]block does not have to be within a macro definition.
 
'''Example'''
 
In this example, the assembler produces the code '''DB'''1 through '''DB'''10. <br />
 
<pre>FOR    X ,  &lt; 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 &gt;
DB      X
ENDM </pre>
In the next example: <br />
 
<pre>FOR      ARGUMENT , &lt; &quot; first  line &quot; , 13 , 10 ,
&quot; second  line &quot; , 13 , 10 &gt;
DB      ARGUMENT
ENDM </pre>
The assembler produces the code: <br />
 
<pre>DB    &quot; first  line &quot;
DB    13
DB    10
DB    &quot; second  line &quot;
DB    13
DB    10 </pre>
<br />
 
[[[00690.htm|prev]]][[[00692.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FORC/IRPC (Iterative Macro Expansion Using List of Characters) ===
 
The assembler repeats the statements in the block once for each character in the string. Each repetition substitutes the next character in the string for every occurrence of ''Parameter''in the block.
 
'''Syntax'''
 
<br />
 
<pre>FORC  Parameter ,  String  ( or  &lt; String &gt; )
    .
    .
    .
ENDM </pre>
'''Remarks'''
 
The obsolete spelling for the '''FORC'''directive is '''IRPC'''.
 
The '''FORC'''directive is similar to the [[00690.htm|FOR/IRP]]directive except that a ''String'' is used instead of &lt;''Argument-List''&gt;, and the angle brackets around the string are optional. The string should be enclosed with angle brackets (&lt;&gt; ) if it contains spaces, commas, or other separating characters.
 
The [[00691.htm|FORC/IRPC]]-[[00688.htm|ENDM]]block does not have to be within a macro definition.
 
'''Example'''
 
In this example, the assembler produces the code '''DB'''1 through '''DB'''8: <br />
 
<pre>FORC      X , 12345678
DB        X
ENDM </pre>
<br />
 
[[[00691.htm|prev]]][[[00693.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== LOCAL (Identify Names Local to a Macro Definition) ===
 
The '''LOCAL'''directive is used inside the body of a macro definition, and provides a method of automatically generating unique assembler labels each time the macro is expanded. The names appearing in the argument list of the '''LOCAL'''directive are known only to the enclosing macro, and each time they are referenced during a macro expansion a unique symbol is created. This prevents the assembler from issuing duplicate definition errors when the macro is expanded more than once and symbols contained therein are being used to create assembler labels.
 
'''Syntax'''
 
<br />
 
<pre>LOCAL  Name  [ ,  Name . . . . ] </pre>
'''Remarks'''
 
The '''LOCAL'''directive is recognized only within the body of a macro given by a [[00693.htm|MACRO]], [[00690.htm|FOR/IRP]], [[00691.htm|FORC/IRPC]], or [[00697.htm|REPEAT/REPT]]definition. The symbols created by the preprocessor are of the form '''??nnnn''', where '''nnnn'''is a hexadecimal number in the range 0000 through FFFF. You must avoid using identifiers of this form for your own purposes, because doing so can cause duplicate definition errors.
 
To insure that they have the proper effect, '''LOCAL'''statements should appear in the body of the macro before any other directives are used. It is acceptable for blank lines or comments to precede any '''LOCAL'''statements.
 
You can use multiple '''LOCAL'''statements if the argument list is too long to fit on one line, or if you want a vertical list of '''LOCAL'''symbols.
 
'''Example'''
 
<br />
 
<pre>DISPLAY  MACRO  TT
 
;  Blank  lines  and  comments  are  ok  here
        LOCAL  AGAIN
 
; ;  DOS  macro  to  display  message  addressed  by  BX  TT  times
        MOV    CX , TT
        MOV    AH , 9
        MOV    DX , BX
; Generate  a  unique  label  for  AGAIN
AGAIN :
        INT    21H
        LOOP    AGAIN
        ENDM </pre>
<br />
 
[[[00692.htm|prev]]][[[00694.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== MACRO (Assign a Body of Text to a Name) ===
 
This directive produces a given sequence of statements from various places in your program, even though different parameters may be required each time you call the sequence.
 
Macro processing consists of two separate and distinct phases: [[00694.htm|Macro Definition]]and [[00695.htm|Macro Expansion]].
 
[[[00693.htm|prev]]][[[00695.htm|next]]][[[00693.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Macro Definition ===
 
A macro definition consists of three essential parts:
 
�The '''MACRO'''directive, defining the ''Name''and the ''Parameter-List'' <br />�The body of the macro, containing the prototypes of statements to produce when you invoke the macro for expansion. <br />�The [[00688.htm|ENDM]]directive, ending the definition of the macro. <br />
 
'''Syntax'''
 
<br />
 
<pre>Name  MACRO  [ Parameter  [ ,  Parameter  . . . ] ]
  .
  .
  .
ENDM </pre>
'''Remarks'''
 
The ''Name''field must be a valid preprocessor identifier and specifies the symbolic name that the user will refer to when invoking the macro for expansion. If ''Name''is already defined, it must be that of a previous macro definition, otherwise an error message is issued. Macros may be redefined to have a different ''Parameter-List''s or macro body text; doing so causes the previous definition to be lost.
 
The optional ''Parameter-List''is the complete comma-separated list of all ''Parameter''valuess given in the macro definition statement. A parameter must be a valid symbol name according to the rules for naming preprocessor and assembler identifiers. Each parameter becomes a symbol that is local to the macro being defined and is recognized during macro expansion prior to searching the global name space. Thus, macro parameters need not have names unique from identifiers defined elsewhere in the program. <br />
 
[[[00694.htm|prev]]][[[00696.htm|next]]][[[00693.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Macro Expansion ===
 
To expand the macro, the macro ''Name''(defined in the ''Name''field of the '''MACRO''' definition statement) is coded as you would any other assembler directive, followed by the list of arguments (if any) that you want to pass to the macro.
 
'''Syntax'''
 
<br />
 
<pre>Name  [ Argument  [ ,  Argument  . . . ] ] </pre>
'''Remarks'''
 
The ''Name''field must be the name of a macro defined previously with a '''MACRO''' directive.
 
Each ''Argument''field denotes a text value that you want to pass to the macro . The relative positions of the elements are important, because each ''Argument''is associated in left-to-right fashion with the corresponding ''Parameter''as defined in the ''Parameter-List''during the macro definition.
 
The number of ''Argument''entries given when the macro is invoked need not be the same as the number of ''Parameter''entries. If you pass extra ''Argument''s to the macro, they are ignored; if too few are supplied, empty text values are associated with the remaining ''Parameter''s. You may also associate an empty text value with a ''Parameter''by passing an explicitly empty text literal &lt;&gt; as an ''Argument''.
 
Commas are normally used to separate arguments, although blanks or tabs are also considered to be argument separators. For this reason, any argument that must contain an argument separator character (commas, blanks, or tabs) should be enclosed in angle brackets &lt;&gt;. For example: <br />
 
<pre>PUSHVEC    MACRO  PARM1 , PARM2
          MOV    AX , PARM1
          PUSH    AX
          MOV    AX , PARM2
          PUSH    AX
          ENDM
          .
          .
          .
          PUSHVEC  DS , &lt; OFFSET  VARNAME &gt;
; PUSH  DWORD  VECTOR  OF  VARNAME  ONTO  STACK </pre>
You can also use angle brackets to produce variable lengths of results. For example: <br />
 
<pre>STRING    MACRO    NUMBERS
          DB        NUMBERS
          ENDM
              .
              .
              .
          STRING  &lt; 1 , 2 , 3 , 4 &gt;
          ; PRODUCE  4  BYTES  OF  INTEGER  NUMBERS </pre>
<br />
 
'''Remarks'''
 
Each time a macro is invoked (expanded) by specifying its name, the preprocessor emits the statements contained in the body of the macro and passes them to the assembler for processing. During the expansion process, any replacement parameters encountered in the macro body (as named in the ''Parameter-List''of the macro definition) are replaced with the corresponding ''Argument''(if any) passed through the ''argument-list''at the time the macro was invoked.
 
'''Example'''
 
<br />
 
<pre>GEN    MACRO    XX , YY , ZZ
      MOV    AX , XX
      ADD    AX , YY
      MOV    ZZ , AX
      ENDM </pre>
When the call is made, for example: <br />
 
<pre>GEN    ED , KISER , SUM </pre>
The assembler produces the following code: <br />
 
<pre>MOV    AX , ED
ADD    AX , KISER
MOV    SUM , AX </pre>
<br />
 
[[[00695.htm|prev]]][[[00697.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== PURGE (Remove Macro Definition) ===
 
The '''PURGE'''directive deletes the definition of a specified macro entry, letting you reuse space.
 
'''Syntax'''
 
<br />
 
<pre>PURGE  Macro - Name [ , . . . ] </pre>
'''Remarks'''
 
It is not necessary to purge a macro before redefining it. You may use '''PURGE'''to recover memory during assembly by deleting the contents of unreferenced macros. An '''Out of Memory'''condition can occur if a large, general-purpose macro library is included.
 
'''Example'''
 
The directive: <br />
 
<pre>PURGE    MACRONAME </pre>
performs the same function as redefining the macro with no contents, as in: <br />
 
<pre>MACRONAME  MACRO
          ENDM </pre>
In the following example, assume that MAC1 is a macro included in MACRO.LIB : <br />
 
<pre>INCLUDE    MACRO . LIB
PURGE      MAC1
MAC1        ;  Calls  the  purged  macro
          ;  but  produces  nothing </pre>
<br />
 
[[[00696.htm|prev]]][[[00698.htm|next]]][[[00687.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== REPEAT/REPT (Iterative Macro Expansion Using a Count Expression) ===
 
'''REPEAT'''specifies the number of times to generate the statements inside the macro.
 
'''Syntax'''
 
<br />
 
<pre>REPEAT  Expression
  Statements
ENDM </pre>
'''Remarks'''
 
The [[00255.htm|''Expression'']]field must evaluate to an [[00599.htm|''Absolute-ExpressionType'']](it cannot contain forward references). Because the repeat block will be expanded at assembler time, the number of iterations must be known then. <br />
 
[[[00697.htm|prev]]][[[00699.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ECHO Directive (Display Message on Standard Output Device) ===
 
The '''ECHO'''directive displays progress through a long assembly or displays the value of conditional assembly parameters.
 
'''Syntax'''
 
<br />
 
<pre>ECHO  Text </pre>
'''Remarks'''
 
The assembler lists the ''Text''entry on the standard output device during assembly when the assembler encounters the '''ECHO'''directive.
 
'''ECHO'''is not available under MASM 5.10 emulation; you must use '''%OUT,'''which is the obsolete spelling for the '''ECHO'''directive.
 
'''Example'''
 
'''Example 1:'''<br />
 
<pre>IF  IBM
    ECHO  IBM  VERSION
    ENDIF
 
IF2
    ECHO  STARTING  SECOND  PASS
    .
    .
    .
    ENDIF </pre>
'''Example 2:'''<br />
 
<pre>INNER    MACRO      TEXT , VAL
        ECHO      TEXT  VAL
        ENDM
        .
        .
        .
HERE      =          $  -  CSEG
        INNER      &lt; CURRENT  LOCATION &gt; , % HERE </pre>
<br />
 
[[[00698.htm|prev]]][[[00700.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== INCLUDE Directive (Insert File Contents into Input Stream) ===
 
The '''INCLUDE'''directive &quot;stacks&quot; the current source file and begins reading tokens from the source file given by the [[00652.htm|''FileName'']]argument. If you use the '''INCLUDE'''directive, you need not repeat a sequence of statements that are common to several source files.
 
'''Syntax'''
 
<br />
 
<pre>INCLUDE  FileName </pre>
'''Remarks'''
 
The assembler uses the following search order when attempting to open the '''INCLUDE'''file:
 
1.If the [[00652.htm|''FileName'']]argument contains a fully qualified path name (one that begins with a back slash or forward slash), then the assembler attempts to open the file exactly as specified, and no other search is performed if the file is not found.
 
2.If the [[00652.htm|''FileName'']]begins with a relative path name or contains no path information, the assembler begins searching for the '''INCLUDE'''file by looking in the directory of the source file that issued the '''INCLUDE'''directive.
 
3.The assembler searches for [[00652.htm|''FileName'']]in the list of directories given by any [[00053.htm|-Fdi]]or [[00053.htm|-I]]options found on the command line.
 
4.The assembler searches for [[00652.htm|''FileName'']]in the list of directories given by the [[00028.htm|&lt;BaseEXE&gt;_INCLUDE]]environment variable.
 
5.The assembler searches for [[00652.htm|''FileName'']]in the list of directories given by the [[00032.htm|INCLUDE]]environment variable.
 
6.Lastly, the assembler searches for [[00652.htm|''FileName'']]in the current directory. If the named file is not found, the assembler issues a fatal error message and the assembler is ended.
 
In no case does the assembler strip relative path information from the [[00652.htm|''FileName'']]when performing search steps 2 through 6.
 
When the file named in the '''INCLUDE'''directive is located, the assembler opens it and assembles all of the statements contained therein until the end of the file is reached. The file is then closed and assembler resumes in the original module at the line following the '''INCLUDE'''directive.
 
An '''INCLUDE'''file should not contain an [[00715.htm|END]]assembler directive to denote the end of the included module; the assembler closes the included module when its physical end of file is reached.
 
'''INCLUDE'''files may be nested to any reasonable level, and is limited only by the operating system's ability to provide the necessary resources.
 
'''Example'''
 
<br />
 
<pre>INCLUDE  OS2 . INC </pre>
<br />
 
[[[00699.htm|prev]]][[[00701.htm|next]]][[[00617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== COMMENT Directive (Program Information Block) ===
 
'''COMMENT'''lets you enter comments about your program without having to enter semicolons (;) for each line.
 
'''Syntax'''
 
<br />
 
<pre>COMMENT  Delimiter  Text  Delimiter </pre>
'''Remarks'''
 
The first non-blank character after '''COMMENT'''is the first delimiter. The '''COMMENT'''directive causes the assembler to treat all ''Text''between ''Delimiter'' and ''Delimiter''as a comment. The text must not contain the delimiter character. This directive is used for multiple-line comments. A '''COMMENT''' defined in the body of a macro does not appear unless '''.LALL'''is requested.
 
'''Example'''<br />
 
<pre>COMMENT  * You  can  enter  as  many  lines
of  text  between  the  delimiters
    .
    .
    .
as  you  need  to  describe  your  program . * </pre>
<br />
 
[[[00700.htm|prev]]][[[00702.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Assembler Directives ===
 
This section describes the various types of ALP directives: <br />
 
<pre>/-----------------------------------------------------------------------------\
|Type                    |Function                |Directives              |
|-------------------------+-------------------------+-------------------------|
|Conditional error        |Debugs programs and      |.ERR                    |
|                        |checks for assembly-time |.ERR1                    |
|                        |errors.                  |.ERR2                    |
|                        |                        |.ERRDEF                  |
|                        |                        |.ERRNDEF                |
|                        |                        |.ERRE                    |
|                        |                        |.ERRNZ                  |
|                        |                        |.ERRB                    |
|                        |                        |.ERRDIF                  |
|                        |                        |.ERRDIFI                |
|                        |                        |.ERRIDN                  |
|                        |                        |.ERRIDNI                |
|                        |                        |.ERRNB                  |
|-------------------------+-------------------------+-------------------------|
|Data allocation          |Allows you to create and |BYTE                    |
|                        |initialize variables for |DB                      |
|                        |use within your program. |DD                      |
|                        |                        |DF                      |
|                        |                        |DQ                      |
|                        |                        |DT                      |
|                        |                        |DW                      |
|                        |                        |DWORD                    |
|                        |                        |FWORD                    |
|                        |                        |QWORD                    |
|                        |                        |REAL4                    |
|                        |                        |REAL8                    |
|                        |                        |REAL10                  |
|                        |                        |SBYTE                    |
|                        |                        |SDWORD                  |
|                        |                        |SWORD                    |
|                        |                        |TBYTE                    |
|                        |                        |WORD                    |
|-------------------------+-------------------------+-------------------------|
|Intermodule linkage      |Simplifies data sharing  |COMM                    |
|                        |and a provides a        |END                      |
|                        |high-level interface to  |EXTERN/EXTRN            |
|                        |multiple-module          |EXTERNDEF                |
|                        |programming.            |INCLUDELIB              |
|                        |                        |NAME                    |
|                        |                        |PUBLIC                  |
|-------------------------+-------------------------+-------------------------|
|Listing control          |Controls the assembler  |%BIN                    |
|                        |listing of your source  |.CREF                    |
|                        |file.                    |.LALL                    |
|                        |                        |.LIST                    |
|                        |                        |.LISTALL                |
|                        |                        |.LISTIF                  |
|                        |                        |.LISTMACRO              |
|                        |                        |.LISTMACROALL            |
|                        |                        |.NOCREF                  |
|                        |                        |.NOLIST                  |
|                        |                        |.NOLISTIF                |
|                        |                        |.NOLISTMACRO            |
|                        |                        |PAGE                    |
|                        |                        |.SALL                    |
|                        |                        |.SFCOND                  |
|                        |                        |SUBTITLE                |
|                        |                        |SUBTTL                  |
|                        |                        |.TFCOND                  |
|                        |                        |TITLE                    |
|                        |                        |.XALL                    |
|                        |                        |.XCREF                  |
|                        |                        |.XLIST                  |
|-------------------------+-------------------------+-------------------------|
|Procedure control        |Allows you to organize  |PROC                    |
|                        |your code into          |LOCAL                    |
|                        |procedures.              |ENDP                    |
|-------------------------+-------------------------+-------------------------|
|Processor control        |Selects processors and  |.186                    |
|                        |coprocessors.            |.286                    |
|                        |                        |.286P                    |
|                        |                        |.287                    |
|                        |                        |.386                    |
|                        |                        |.386P                    |
|                        |                        |.387                    |
|                        |                        |.486                    |
|                        |                        |.486P                    |
|                        |                        |.586                    |
|                        |                        |.586P                    |
|                        |                        |.686                    |
|                        |                        |.686P                    |
|                        |                        |.8086                    |
|                        |                        |.8087                    |
|                        |                        |.MMX                    |
|                        |                        |.NOMMX                  |
|-------------------------+-------------------------+-------------------------|
|Segments                |Creates and manages      |ALIGN                    |
|                        |segments.                |.ALPHA                  |
|                        |                        |.CODE                    |
|                        |                        |.CONST                  |
|                        |                        |.DATA                    |
|                        |                        |.DATA?                  |
|                        |                        |DOSSEG                  |
|                        |                        |.DOSSEG                  |
|                        |                        |ENDS                    |
|                        |                        |EVEN                    |
|                        |                        |.FARDATA                |
|                        |                        |.FARDATA?                |
|                        |                        |GROUP                    |
|                        |                        |.MODEL                  |
|                        |                        |ORG                      |
|                        |                        |SEGMENT                  |
|                        |                        |.SEQ                    |
|                        |                        |.STACK                  |
|-------------------------+-------------------------+-------------------------|
|Type definition          |Allows the creation of  |RECORD                  |
|                        |complex user-defined data|STRUC                    |
|                        |types.                  |STRUCT                  |
|                        |                        |TYPEDEF                  |
|                        |                        |UNION                    |
|-------------------------+-------------------------+-------------------------|
|Miscellaneous            |Provides miscellaneous  |=                        |
|                        |functions.              |.ABORT                  |
|                        |                        |ASSUME                  |
|                        |                        |EQU                      |
|                        |                        |LABEL                    |
|                        |                        |OPTION                  |
|                        |                        |.RADIX                  |
\-----------------------------------------------------------------------------/</pre>
[[[00701.htm|prev]]][[[00703.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Conditional Error Control ===
 
Use conditional error control directives to debug programs and check for assembly-time errors. If you insert a conditional assembly directive in your code, you can test assembly-time conditions at that point. You can also test for boundary conditions in macros by using conditional error control directives.
 
Errors generated by conditional error control directives cause ALP to return a nonzero return code. If a severe error is detected during assembly , ALP does not generate the object module.
 
This section describes the following conditional error control directives:
 
.ERR <br />.ERR1 <br />.ERR2 <br />.ERRB <br />.ERRDEF <br />.ERRDIF <br />.ERRDIFI <br />.ERRE <br />.ERRIDN <br />.ERRIDNI <br />.ERRNB <br />.ERRNDEF <br />.ERRNZ <br />
 
[[[00702.htm|prev]]][[[00704.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERR/.ERR1/.ERR2 (Force Assembly Error Condition) ===
 
The '''.ERR''', '''.ERR1''', and '''.ERR2'''directives cause errors at the points at which they occur in the source file.
 
'''Syntax'''
 
<br />
 
<pre>. ERR
    or
. ERR1
    or
. ERR2 </pre>
'''Remarks'''
 
The '''.ERR'''directive causes an error regardless of the pass. '''.ERR1'''causes an error on the first pass only. '''.ERR2'''causes an error on the second pass only. If you use the '''-Lp:1'''option to request a first pass listing, the '''. ERR1'''error message appears on the screen and in the listing file. Like other error conditions occurring during pass one, the error generated by '''. ERR1'''does not cause the assembly to fail.
 
'''Example'''
 
This example ensures that you define either the DOS or the OS2 symbol. If you define neither, the assembler assembles the nested '''ELSE'''condition and produces an error message. The '''.ERR'''directive causes an error on each pass. <br />
 
<pre>IFDEF  DOS
      .
      .
      .
ELSE
      IFDEF  OS2
          .
          .
          .
      ELSE
          . ERR
      ENDIF
ENDIF </pre>
<br />
 
[[[00703.htm|prev]]][[[00705.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERRB/.ERRNB (Error if Argument Blank/Non-Blank) ===
 
The '''.ERRB'''and '''.ERRNB'''directives test the given [[00662.htm|''Text-Argument'']].
 
'''Syntax'''
 
<br />
 
<pre>. ERRB  Text - Argument
    or
. ERRNB  Text - Argument </pre>
'''Remarks'''
 
If [[00662.htm|''Text-Argument'']]is blank, the '''.ERRB'''directive produces an error. If [[00662.htm|''Text- Argument'']]is not blank, '''.ERRNB'''produces an error.
 
You can test for the existence of parameters by using these directives within macros.
 
'''Example'''
 
In this example, the directives ensure that only one argument is passed to the macro. If no argument is passed to the macro, the '''.ERRB'''directive produces an error. If more than one argument is passed, the '''.ERRNB''' directive produces an error. <br />
 
<pre>WORK      MACRO      REALARG , TESTARG
        . ERRB      &lt; REALARG &gt;    ; ;  Error  if  no  parameters
        . ERRNB    &lt; TESTARG &gt;    ; ;  Error  if  more  than  one  parameter
                  .
                  .
                  .
        ENDM </pre>
<br />
 
[[[00704.htm|prev]]][[[00706.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERRDEF/.ERRNDEF (Error if Symbol Defined/Not Defined) ===
 
The '''.ERRDEF'''and '''.ERRNDEF'''directives test whether a symbol has been defined.
 
'''Syntax'''
 
<br />
 
<pre>. ERRDEF  Identifier
    or
. ERRNDEF  Identifier </pre>
'''Remarks'''
 
If [[00149.htm|''Identifier'']]is defined as a label, a variable, or a symbol, the '''.ERRDEF''' directive produces an error. If you have not defined [[00149.htm|''Identifier'']], '''.ERRNDEF''' produces an error. When [[00149.htm|''Identifier'']]is a forward reference, the assembler considers it undefined on the first pass and defined on the second pass.
 
'''Example'''
 
In this example, '''.ERRDEF'''ensures that '''SYMBOL'''is not defined before entering the blocks, and '''.ERRNDEF'''ensures that you defined '''SYMBOL'''somewhere within the blocks. <br />
 
<pre>. ERRDEF      SYMBOL
IFDEF        CONFIG1
            .
            .    SYMBOL  EQU  0
            .
ENDIF
IFDEF        CONFIG2
            .
            .    SYMBOL    EQU  1
            .
ENDIF
. ERRNDEF      SYMBOL </pre>
<br />
 
[[[00705.htm|prev]]][[[00707.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERRDIF/.ERRDIFI (Error if Arguments are Different) ===
 
The '''.ERRDIF'''and '''.ERRDIFI'''directives generate an assembler error if the two [[00662.htm|''Text-Argument'']]''s''are different.
 
'''Syntax'''
 
<br />
 
<pre>. ERRDIF  Text - Argument - 1 ,  Text - Argument - 2
    or
. ERRDIFI  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
The '''.ERRDIF'''directive performs a case-sensitive comparision, and the '''. ERRDIFI'''directive performs a case-insensitive comparision.
 
'''Example'''
 
In this example, a check is made to verify that the currently opened segment is '''_TEXT'''. This helps to insure that the macro is used only from within the default near code segment, and not from a program with a memory model that uses far code pointers (MEDIUM, LARGE, or HUGE). <br />
 
<pre>RETURN  MACRO
    ; ;  Use  the  expansion  operator  ( % )  to  resolve  @ CurSeg  equate
    %  . errdif  &lt; _ TEXT &gt; , &lt; @ CurSeg &gt;    ; ;  Must  be  in  near  . CODE  segment
    RETN                            ; ;  Force  a  near  return
ENDM </pre>
<br />
 
[[[00706.htm|prev]]][[[00708.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERRE/.ERRNZ (Error if Expression False/True) ===
 
The '''.ERRE'''and '''.ERRNZ'''directives test the value of an [[00255.htm|''Expression'']].
 
'''Syntax'''
 
<br />
 
<pre>. ERRE  Expression
    or
. ERRNZ  Expression </pre>
'''Remarks'''
 
If the [[00255.htm|''Expression'']]evaluates to be false (zero), the '''.ERRE'''directive produces an error. If the [[00255.htm|''Expression'']]evaluates to be true (not zero), the '''.ERRNZ'''directive produces an error. The [[00255.htm|''Expression'']]must evaluate to an absolute value and cannot contain forward references.
 
'''Example'''
 
In this example, '''.ERRE'''checks the boundaries of a parameter that the program passes to the macro '''BUFFER'''. If count is less than or equal to 128, the expression that the directive tests is true (not zero) and the directive produces no error. If '''COUNT'''is greater than 128, the expression is false (zero) and the directive produces an error. <br />
 
<pre>BUFFER  MACRO    COUNT , BNAME
        . ERRE    COUNT  LE  128
        BNAME  DB  COUNT  DUP  ( 0 )  ; ;  Reserve  memory ,  but  no  more  than  128  bytes
        ENDM
 
BUFFER  128 , BUF1    ;  Data  reserved  -  no  error
BUFFER  129 , BUF2    ;  Error  produced </pre>
<br />
 
[[[00707.htm|prev]]][[[00709.htm|next]]][[[00702.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ERRIDN/.ERRIDNI (Error if Arguments are Identical) ===
 
The '''.ERRIDN'''and '''.ERRIDNI'''directives generate an assembly error if the two [[00662.htm|''Text-Argument'']]''s''are identical.
 
'''Syntax'''
 
<br />
 
<pre>. ERRIDN  Text - Argument - 1 ,  Text - Argument - 2
    or
. ERRIDNI  Text - Argument - 1 ,  Text - Argument - 2 </pre>
'''Remarks'''
 
The '''.ERRIDN'''directive performs a case-sensitive comparision, and the '''. ERRIDNI'''directive performs a case-insensitive comparision.
 
'''Example'''
 
In this example, '''.ERRIDN'''protects against the passing the AX register as the second parameter, because the macro does not work if this happens. This example uses the '''.ERRIDNI'''directive since the macro needs to check for all possible spellings of the AX register. <br />
 
<pre>ADDEM    MACRO  AD1 , AD2 , SUM
        . ERRIDNI  &lt; ax &gt; , &lt; AD2 &gt;  ; ;  ERROR  IF  AD2  is  ax
        MOV        AX , AD1      ; ;  Would  overwrite  if  AD2  were  AX
        ADD        AX , AD2
        MOV        SUM , AX      ; ;  SUM  must  be  register  or  memory
ENDM </pre>
<br />
 
[[[00708.htm|prev]]][[[00710.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Data Allocation ===
 
Data allocation statements allow you to reserve storage for your program data. To initiate a data allocation statement, an '''''Old-Style-Allocation- Directive''may be used, but in modes other than [[00105.htm|M510]]it is preferable to use a [[00125.htm|''Scalar-TypeName'']]or [[00171.htm|''UserDefined-TypeName'']], which the assembler treats as a pseudo-directive. To introduce consistency into the descriptions, all such variations will be referred to as the '''''Allocation-TypeName''.''''''
 
The ''Allocation-TypeName''that you select determines the data-type of the allocated storage. An optional symbolic name may be associated with the storage, and the storage may also be initialized with specific values if so desired.
 
'''Syntax'''
 
<br />
 
<pre>[ Name ]  Allocation - TypeName  Initializer  [ ,  Initializer  . . . ] </pre>
Allocation-TypeName'':'' <br />''Old-Style-Allocation-Directive'' <br />[[00125.htm|''Scalar-TypeName'']] <br />[[00172.htm|''Record-TypeName'']] <br />[[00173.htm|''Structure-TypeName'']] <br />[[00175.htm|''Union-TypeName'']] <br />[[00174.htm|''Typedef-TypeName'']] <br />
 
'''''Old-Style-Allocation-Directive:''one of <br />'''<br />''''''
 
<pre>DB DW DD DF DQ DT</pre>
<br />
 
'''Remarks'''
 
The various fields of the data allocation statement are described as follows:
 
'''''Name''If the ''Name''entry is present, it must be specified as a valid [[00149.htm|''Identifier'']]unique to the scope in which it appears. If the allocation statement is assembled into an open segment, the assembler converts the identifier to a [[00167.htm|''Data-LabelName'']]to allow referencing the storage by a symbolic variable name. If the allocation statement is assembled into the body of a [[00782.htm|STRUCT]]or [[00784.htm|UNION]]type definition, then the assembler converts the identifier to a [[00160.htm|''Structure-FieldName'']]or [[00161.htm|''Union-FieldName'']].'''
 
'''''Allocation-TypeName''If the ''Allocation-TypeName''is specified as a [[00174.htm|''Typedef- TypeName'']], the assembler ''resolves''it to its underlying data type to determine what type of initialization is to be performed.'''
 
If the ''Allocation-TypeName''entry resolves to a [[00125.htm|''Scalar-TypeName'']]or a pointer to some other type, then the ''Initializer''field must be specified using an expression syntax that can be resolved to a [[00614.htm|''Scalar-Initializer- ExpressionType'']]. See the following section on [[00710.htm|Initialization of Scalar Types]]for a full description of this topic.
 
If the ''Allocation-TypeName''entry resolves to a [[00172.htm|''Record-TypeName'']], [[00173.htm|''Structure- TypeName'']], or [[00175.htm|''Union-TypeName'']], then the ''Initializer''field must be specified using the [[00579.htm|''Compound-Initializer'']]syntax. See the following section on [[00711.htm|Initialization of Aggregate Types]]for a full description of this topic.
 
If the ''Allocation-TypeName''entry resolves to an array of any other type, then the ''Initializer''field must be specified using the [[00579.htm|''Compound-Initializer'']] syntax. See the following section on [[00712.htm|Initialization of Vector Types]]for a full description of this topic.
 
'''''Initializer''Each ''Initializer''entry is an [[00255.htm|''Expression'']]that must resolve to an [[00614.htm|''Initializer-ExpressionType'']]appropriate for the type of data described by the ''Allocation-TypeName''field.'''
 
Each ''Initializer''entry may also be duplicated by making it the operand of a [[00258.htm|''Duplicative-Expression'']]. When assembling in [[00105.htm|ALP]]mode however, the '''DUP''' operator is considered obsolete and its use is discouraged. Instead, a [[00174.htm|''Typedef-TypeName'']]associated with the declaration of a true array should be used in the ''Allocation-TypeName''field along with the appropriate compound initializer. <br />
 
[[[00709.htm|prev]]][[[00711.htm|next]]][[[00709.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Initialization of Scalar Types ===
 
A scalar data item represents a numeric quantity that may be increased or decreased in magnitude as a single unit. Thus, an ''Initializer''expression for a scalar data item must be coded such that it resolves to a single scalar value. See the section on [[00614.htm|''Scalar-Initializer-ExpressionType'']]for the syntax and semantics of such expressions.
 
The old-style allocation directives (DB, DW, DD, DF, DQ, and DT) are supported in all assembler emulation modes, but for modes other than [[00105.htm|M510]], the [[00125.htm|''Scalar-TypeName'']]keywords should be used instead.
 
When the [[00125.htm|''Scalar-TypeName'']]keywords are used instead of the old-style allocation directives, the assembler has full knowledge of the data types of the variables being created. This allows the assembler to make more intelligent code generation decisions, and it enables the assembler to correctly describe the variable in the symbolic debugging information that it generates for the source level debugger. [[00125.htm|''Scalar-TypeName'']]''s''may only be used as allocation directives in the [[00105.htm|ALP]]or [[00105.htm|M600]]modes.
 
To allocate an uninitialized scalar data item, use the [[00140.htm|''Indeterminate-Value- Alias'']]($) in the ''Initializer''field. <br />
 
<pre>/-----------------------------------------------------------------------\
|Type Name|Data Type          |Initializer Description                |
|---------+--------------------+----------------------------------------|
|DB, BYTE,|Allocates 8-bit    |Each Initializer must be in the range  |
|or SBYTE |(byte) values.      |from 0 to 255 (unsigned) for a DB or    |
|        |                    |BYTE directive, and from -128 to 127    |
|        |                    |(signed) for a SBYTE directive.        |
|---------+--------------------+----------------------------------------|
|DW, WORD,|Allocates 16-bit    |Each Initializer must be in the range  |
|or SWORD |(word) values.      |from 0 to 65535 (unsigned) for a DW or  |
|        |                    |WORD directive, and from -32768 to 32767|
|        |                    |(signed) for a SWORD directive.        |
|---------+--------------------+----------------------------------------|
|DD,      |Allocates 32-bit    |If the Initializer is an integer, each  |
|DWORD, or|(double-word)      |must be in the range from 0 to          |
|SDWORD  |values.            |4,294,967,295 (unsigned) for a DD or    |
|        |                    |DWORD directive, and from -2,147,483,648|
|        |                    |to 2,147,483,647 (signed) for a SDWORD  |
|        |                    |directive.  If the DD directive is being|
|        |                    |used, an Initializer may also resolve to|
|        |                    |a 32-bit Floating-Point-ExpressionType. |
|---------+--------------------+----------------------------------------|
|DF or    |Allocates 48-bit    |Each Initializer typically specifies the|
|FWORD    |(6-byte far-word)  |full address of a 32-bit far code or    |
|        |values.            |data label, but normal 32-bit integer  |
|        |                    |values may also be used.  The processor |
|        |                    |does not support 48-bit integer        |
|        |                    |operations, thus the assembler does    |
|        |                    |support 48-bit integer precision when  |
|        |                    |initializing such variables.  These    |
|        |                    |directives are typically only useful for|
|        |                    |defining pointer variables for use on  |
|        |                    |32-bit processors.                      |
|---------+--------------------+----------------------------------------|
|DQ or    |Allocates 64-bit    |Both DQ and QWORD allow an integer      |
|QWORD    |(quad-word) values. |Initializer with 64-bit (8-byte)        |
|        |                    |precision.  If the DQ directive is being|
|        |                    |used, the Initializer field may resolve |
|        |                    |to a 64-bit                            |
|        |                    |Floating-Point-ExpressionType.          |
|---------+--------------------+----------------------------------------|
|DT or    |Allocates 80-bit    |Both DT and TBYTE allow an integer      |
|TBYTE    |(10-byte) values    |Initializer with 80-bit (10-byte)      |
|        |                    |precision.  If the DT directive is being|
|        |                    |used, the Initializer field may resolve |
|        |                    |to a 80-bit                            |
|        |                    |Floating-Point-ExpressionType.          |
|---------+--------------------+----------------------------------------|
|REAL4,  |Allocates real      |Each Initializer must resolve to a      |
|REAL8, or|(floating-point)    |Floating-Point-ExpressionType.  The    |
|REAL10  |values of a specific|assembler converts the floating-point  |
|        |size (4 bytes, 8    |literal to the IEEE format appropriate  |
|        |bytes, or 10 bytes).|for the type of variable being          |
|        |                    |allocated.                              |
\-----------------------------------------------------------------------/</pre>
'''Examples'''
 
Here are some examples of scalar initialization: <br />
 
<pre>;  Allocate  some  integer  variables
uint8        BYTE        0 ,  255                ;  min ,  max  values  for  unsigned  byte
sint8        SBYTE      - 128 ,  127            ;  min ,  max  values  for  signed  byte
USHORT _ T    TYPEDEF    WORD                  ;  Define  a  typedef  alias  for  WORD
ushort      USHORT _ T    0 ,  0FFFFh            ;  and  use  it  as  allocation  type  name
 
;  Some  things  to  know  about  string - literal  initializers
char        BYTE        &quot; a &quot;                  ;  a  single  BYTE  value  ( 061h )
is _ int      WORD        &quot; ab &quot;                  ;  a  single  WORD  value  ( 06162h )
this _ too    DWORD      &quot; abcd &quot;                ;  a  single  DWORD  value  ( 061626364h )
too _ long    WORD        &quot; abcd &quot;                ;  error ,  expression  too  big  for  a  word
string      BYTE        &quot; string &quot; ,  0          ;  but  strings  can  allocate  many  bytes
 
;  Integers ,  pointers ,  and  old - style  initializations
PDWORD _ T    TYPEDEF    PTR  DWORD            ;  First ,  define  a  pointer  type
ulong        DWORD      0 ,  0FFFFFFFFh        ;  min ,  max  values  for  unsigned  dword
pulong      PDWORD _ T    OFFSET  ulong        ;  pointer  to  the  ulong  variable
old _ style    DD          1 . 314                ;  old  style ,  floats  are  accepted
new _ int      SDWORD      1 . 314                ;  new  style ,  error - must  use  integers
new _ real    REAL4      1314                  ;  new  style ,  error - must  use  floats
 
;  Allocate  some  real  numbers  using  decimal  floating - point  literals
float _ f      REAL4      123 . 45                ;  4 - byte  IEEE  real
double _ f    REAL8      98 . 7654E1            ;  8 - byte  IEEE  real
longdbl _ f    REAL10      1000 . 0E - 2            ; 10 - byte  IEEE  real
 
;  The  same  values  using  hexdecimal  floating - point  literals
float _ h      REAL4    42F6E666r                ;  4 - byte  IEEE  real
double _ h    REAL8    408EDD3B645A1CACr      ;  8 - byte  IEEE  real
longdbl _ h    REAL10  4002A000000000000000r  ; 10 - byte  IEEE  real </pre>
<br />
 
[[[00710.htm|prev]]][[[00712.htm|next]]][[[00709.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Initialization of Aggregate Types ===
 
An aggregate data item is a collection of one or more sub-items of possibly dissimilar types that are allocated, initialized, and treated as a single unit. The sub-items usually have unique names, and their positions relative to other sub-items is significant. The assembler provides the ability to define aggregate types through use of the [[00781.htm|RECORD]], [[00782.htm|STRUCT]], and [[00784.htm|UNION]]directives.
 
Initialization of an aggregate data item requires a programming notation that isolates the entire aggregate from surroundings constructs, and denotes the position of each sub-item within the aggregate. The syntax for this construct is as follows:
 
''Aggregate-Initializer'''':'' <br />'''{'''[''Initializer-List''] '''}''' <br />'''&lt;'''[''Initializer-List''] '''&gt;''' <br /> <br />''Initializer-List'''':'' <br />''Initializer-Item'' <br />''Initializer-List'', [''LineBreak''] ''Initializer-Item'' <br /> <br />''Initializer-Item'''':'' <br />[''Scalar-Initializer''] <br />[''Aggregate-Initializer''] <br />[''Array-Initializer''] <br /> <br />
 
The syntax requires that an ''Aggregate-Initializer''be enclosed in an outer set of braces or angle brackets, but the ''Initializer-List''or individual comma-separated ''Initializer-Item''s may be left unspecified, in which case a default initializer value is used. Commas are used to denote the position of each sub-item within the entire aggregate, and nested initializers are allowed to accomodate imbedded occurrences of other aggregates (or vector types, which share the same initializer syntax).
 
When initializing an instance of a union, the assembler only allows an initializer to be specified for the first field defined in the union type.
 
'''Examples'''
 
Here are some examples of aggregate initialization: <br />
 
<pre>YES    equ    1
NO      equ    0
MAYBE  equ  - 1
 
BOOL _ T  typedef  sbyte
 
IDEAS _ T  struct
  sanctum    BOOL _ T  ?            ;  For  scalar  data ,  use  the  ?  operator
  peace      BOOL _ T  ?            ;    to  request  an  uninitialized  value .
  pilzner    BOOL _ T  ?
IDEAS _ T  ends
 
PROBLEM _ T  struct
    work    BOOL _ T    YES          ;  Establish  default  initial  values  that
    car      BOOL _ T    NO          ;    can  be  inherited  when  an  instance  of
    house    BOOL _ T    MAYBE        ;    the  structure  is  allocated
PROBLEM _ T  ends
 
SOLUTION _ T  struct
    fixing  PROBLEM _ T  { }        ;  Outermost  set  of  braces  required  even
            IDEAS _ T    { }        ;    with  unspecified  ( default )  initializers
SOLUTION _ T  ends
 
DATA  segment
  ProblemWith  PROBLEM _ T    {  NO ,  ,  MAYBE  }          ;  First - level  structure
  ThinkOf      SOLUTION _ T  {  {  YES ,  YES ,  YES  } ,      ;  Intializer  syntax  for
                              {    NO ,    NO ,    NO  }  }    ;    imbedded  structures
DATA  ends
 
CODE    segment
        assume  ds : DATA
        mov  al ,  NO
        or    al ,  ProblemWith . work
        or    al ,  ProblemWith . car
        or    al ,  ProblemWith . house
        jz    exit
        mov  ThinkOf . fixing . work ,  NO      ;  References  to  named  fields  in
        mov  ThinkOf . fixing . car ,  NO        ;    imbedded  structures  must  be
        mov  ThinkOf . fixing . house ,  NO      ;    fully  qualified .
exit :    mov  ThinkOf . pilzner ,  YES          ;  Reference  to  &quot; promoted &quot;  field
        ret
CODE    ends
end </pre>
<br />
 
[[[00711.htm|prev]]][[[00713.htm|next]]][[[00709.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Initialization of Vector Types ===
 
A vector data item is a linear collection of one or more sub-items of identical type that are allocated, initialized, and treated as a single unit. A vector (more commonly referred to as an '''''array'') is defined to have a specific number of items '''''n'', which are numbered from '''''0''to '''''n - 1''and occupy a contiguous area of allocated storage. The items in the vector may be of any type, possibly even other vectors (commonly known as a '''''multi- dimensional array''). The assembler provides the ability to define vector types through the use of the standard [[00250.htm|''Type-Declaration'']]syntax.'''''''''''''''
 
The syntax required to initialize a vector is similar to that used for an aggegrate data type, and is as follows:
 
''Array-Initializer'''':'' <br />'''{'''[''Initializer-List''] '''}''' <br />'''&lt;'''[''Initializer-List''] '''&gt;''' <br /> <br />''Initializer-List'''':'' <br />''Initializer-Item'' <br />''Initializer-List'', [''LineBreak''] ''Initializer-Item'' <br /> <br />''Initializer-Item'''':'' <br />[''Scalar-Initializer''] <br />[''Aggregate-Initializer''] <br />[''Array-Initializer''] <br /> <br />
 
The syntax requires that an ''Array-Initializer''be enclosed in an outer set of braces or angle brackets, but the ''Initializer-List''or individual comma- separated ''Initializer-Item''s may be left unspecified, in which case a default initializer value is used. Commas are used to denote the position of each sub-item within the entire array, and nested initializers are allowed to accomodate imbedded occurrences of other arrays (or aggregate types, which share the same initializer syntax).
 
'''Examples'''
 
Here are some examples of vector initialization: <br />
 
<pre>;  Data  structures  to  define  a  &quot; computer &quot;  data  type
 
TRUE        equ          1
FALSE        equ          0
MB          equ      1024                  ;  Megabytes
 
BOOL _ T      typedef  BYTE                  ;  true  or  false  value
INCHES _ T    typedef  BYTE                  ;  number  of  inches
MONITOR _ T    typedef  INCHES _ T              ;  size  of  monitor  in  inches
KEYBOARD _ T  typedef  BOOL _ T                ;  is  a  keyboard  installed ?
MOUSE _ T      typedef  BOOL _ T                ;  is  a  mouse  installed ?
KBYTES _ T    typedef  WORD                  ;  number  of  kilobytes
MBYTES _ T    typedef  WORD                  ;  number  of  megabytes
FPRESENT _ T  typedef  BOOL _ T [ 2 ]              ;  up  to  two  floppies  installed
FSIZE _ T      typedef  KBYTES _ T [ 2 ]          ;  how  big  they  are
DPRESENT _ T  typedef  BOOL _ T [ 4 ]              ;  up  to  four  hardfiles  installed
DSIZE _ T      typedef  MBYTES _ T [ 4 ]          ;  how  big  they  are
RAM _ T        typedef  DWORD                  ;  how  much  memory  we  have
NAME _ T      typedef  BYTE [ 64 ]              ;  what  we  call  the  system
 
FLOPPIES _ T  struct
DriveCount  FPRESENT _ T  {  TRUE ,  FALSE  }    ;  assume  one  floppy  installed
DriveSize    FSIZE _ T      {  360 ,  0  }        ;  assume  360KB  in  size  : - )
FLOPPIES _ T  ends
 
DRIVES _ T    struct
DriveCount  DPRESENT _ T  {  TRUE ,  FALSE ,  FALSE ,  FALSE  }    ;  one  drive  installed
DriveSize    DSIZE _ T      {  20 ,  0 ,  0 ,  0  }                    ;  20MB  in  size  ( ! )
DRIVES _ T    ends
 
COMPUTER _ T  struct
Monitor      MONITOR _ T    14                ;  Assume  a  14  inch  monitor
Keyboard    BOOL _ T        TRUE              ;  We  have  a  keyboard
Mouse        BOOL _ T        FALSE              ;  but  no  mouse
Memory      RAM _ T        640                ;  Assume  640KB
Floppies    FLOPPIES _ T    { }                ;  Go  with  the  defaults
HardFiles    DRIVES _ T      { }                ;  Go  with  the  defaults
ModelName    NAME _ T        { }                ;  No  default  name
COMPUTER _ T  ends
 
DATA  segment
Circa1997    COMPUTER _ T    \                  ;  initializer  begins  on  next  line
  {  17 ,                                    ;  of  course ,  we  have  a  17 &quot;  monitor
    TRUE ,  TRUE ,                            ;  a  keyboard  and  a  mouse
    32  *  MB ,                              ;  32  Megabytes  of  ram
    {  {  } ,                                ;  still  one  floppy
      {  1440  }  } ,                          ;  but  it  has  a  1 . 2  MB  capacity
    {  {  ,  TRUE ,  TRUE  } ,                  ;  also  have  second  and  third  hardfiles
      {  512 ,  1024 ,  4096  }  } ,              ;  512MB ,  1  GIG ,  and  4  GIG
    {  &quot; Spiffatron  9000 &quot; ,  10 ,  13 ,        ;  with  a  fancy  system  name
      &quot; Acme  Computers &quot; ,  10 ,  13 ,  0  }  }
DATA  ends
end </pre>
<br />
 
[[[00712.htm|prev]]][[[00714.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Intermodule Linkage ===
 
To use symbols and procedures in more than one module, ALP must recognize shared data as global to all modules. ALP provides directives to simplify data sharing and a high-level interface to multiple-module programming. With these directives, you can define shared symbols and refer to them from other modules.
 
This section describes the following intermodule linkage directives:
 
COMM <br />END <br />EXTERN/EXTRN <br />EXTERNDEF <br />INCLUDELIB <br />NAME <br />PUBLIC <br />
 
[[[00713.htm|prev]]][[[00715.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== COMM (Declare Communal Variable) ===
 
Declares an uninitialized '''''common''or '''''communal''variable that is allocated by the linker.''''''
 
'''Syntax'''
 
<br />
 
<pre>COMM  [ Language - Name ]  [ Distance ]  Name [ [ Count ] ] : TypeName [ : Size ]  [ ,  . . . ] </pre>
'''Remarks'''
 
The arguments to the '''COMM'''directive are as follows:
 
[[00131.htm|''Language-Name'']]Optional parameter that determines how ''Name''is spelled when written to the object file. Used when interfacing with routines written in high-level languages. If not specified, the language defaults to the value set by [[00775.htm|.MODEL]]or [[00793.htm|OPTION LANGUAGE]].
 
'''''Distance''One of '''NEAR'''or '''FAR'''; determines the distance of allocated variable. If not specified, the current memory model determines the distance. The default is '''NEAR'''if no memory model is active.'''
 
'''''Name''The name of the variable to be allocated by the linker. This field is required.'''
 
'''''[Count]''Optional; if specified, this parameter must be surrounded by square brackets. The ''Count''parameter can be thought of as a major (row) array dimension. It defaults to 1 if not specified.'''
 
'''''TypeName''Required parameter that specifies the type of the variable being allocated. It must be a single keyword or identifier that specifies a [[00128.htm|''Distance-TypeName'']], [[00125.htm|''Scalar-TypeName'']], or [[00171.htm|''UserDefined-TypeName'']].'''
 
'''''Size''''Size''is an optional parameter that can be thought of as a minor ( column) array dimension. It defaults to 1 if not specified.'''
 
Communal variables are allocated by the linker. When the linker combines object modules together, all instances of an identically-named communal variable are merged into a single instance (union), and are uninitialized.
 
The allocated size of a communal variable is the largest size requested by all encountered references.
 
The allocation order with respect to the addresses of other global symbols is undefined; an application must not depend on the address of a communal variable being less than or greater than that of another global symbol.
 
A variable allocated with the '''COMM'''directive need not be declared in all referencing modules as communal; the linker matches all [[00716.htm|EXTERN/EXTRN]] references with that of the communal variable. Similarly, a variable allocated in one module with the [[00720.htm|PUBLIC]]directive may be declared in other modules as communal.
 
Since communal variables cannot be initialized and their address positions cannot be compared, use of the '''COMM'''directive is discouraged. The [[00717.htm|EXTERNDEF]]directive should be used instead. <br />
 
[[[00714.htm|prev]]][[[00716.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== END (Define End of Module and Entry Point) ===
 
The '''END'''directive has two functions:
 
�Identifies the end of the source program. <br />�Identifies the symbol that is the name of the entry point (through the [[00255.htm|''Expression'']]on the '''END'''directive) <br />
 
'''Syntax'''
 
<br />
 
<pre>END  [ Expression ] </pre>
'''Remarks'''
 
All source files must have the '''END'''directive as the last statement. Any lines following the '''END'''statement are ignored by the assembler.
 
When the linker builds an application program from one or more object modules, it needs to know where the entry point is for the operating system to pass initial control. If you do not specify an entry point, none is assumed. Only one module can identify a label as the entry point by specifying that label on its '''END'''statement. Any module not defining an operating system entry point must not have an entry point identified on its '''END'''statement. If you fail to define an entry point for the main module, your program may not be able to initialize correctly. It will assemble and link without error, but it cannot run.
 
'''Example'''
 
The following example is the '''END'''statement for the section of code that starts with the name '''BEGIN'''. <br />
 
<pre>END  BEGIN </pre>
<br />
 
[[[00715.htm|prev]]][[[00717.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EXTERN/EXTRN (Declare External Identifier) ===
 
The '''EXTERN'''directive specifies a declaration for the external symbol ''Name'' so that it may be referred to within this module. The actual definition for the symbol occurs in some other module, and the linker resolves all such external declarations to a single definition for ''Name''.
 
'''Syntax'''
 
<br />
 
<pre>EXTERN  [ Language - Name ]  Name  [ ( Default - Resolution ) ]  : Type  [ ,  . . . ] </pre>
Where ''Type''is one of:
 
�'''ABS''' <br />�[[00250.htm|''Type-Declaration'']]
 
'''Remarks'''
 
The obsolete spelling for the '''EXTERN'''directive is '''EXTRN'''.
 
The external source module that defines the symbol must give it public visibility in the corresponding object module, which is accomplished in assembler language by declaring it with the [[00714.htm|COMM]]directive, defining the symbol in association with an [[00717.htm|EXTERNDEF]]or [[00720.htm|PUBLIC]]directive, or by specifying the '''PUBLIC'''or '''EXPORT'''attributes in a [[00739.htm|PROC]]directive.
 
If the '''EXTERN'''directive is given within a segment, the assembler assumes that the symbol is located within that segment. If the segment is not known, place the '''EXTERN'''directive outside all segments and either use an explicit segment prefix or an '''ASSUME'''directive.
 
A ''Type''value of '''ABS'''indicates that ''Name''is an externally-defined constant value. Local references to ''Name''are treated as immediate values having an [[00587.htm|''Operand Size'']]equal to the [[00586.htm|''Address Size'']]of the segment containing the reference.
 
'''Note:'''If the ''Type''of '''EXTERN'''is '''ABS''', it may not be used anywhere in this module where conversion to an immediate value of type '''BYTE'''is required. Additionally, the defining module must define the value as a constant symbol.
 
'''For example:'''<br />
 
<pre>FOO      EQU      5
PUBLIC  FOO </pre>
Use of the ''(default_resolution)''syntax declares the external symbol ''Name''to be a &quot;weak&quot; symbol, in which case the linker will pair all such declarations with the symbol ''default_resolution''unless a standard &quot;strong&quot; public definition for ''Name''is encountered during the link.
 
'''Example'''<br />
 
<pre>/-----------------------------------------------------------------------\
|IN THE SAME SEGMENT                |IN ANOTHER SEGMENT                |
|-----------------------------------+-----------------------------------|
|IN MODULE 1:                      |IN MODULE 1:                      |
|                                  |                                  |
|cseg segment                      |csega segment                      |
|public tagn                        |public tagf                        |
|.                                  |.                                  |
|.                                  |.                                  |
|.                                  |.                                  |
|tagn:                              |tagf:                              |
|.                                  |.                                  |
|.                                  |.                                  |
|.                                  |.                                  |
|cseg ends                          |csega ends                        |
|                                  |                                  |
|IN MODULE 2:                      |IN MODULE 2:                      |
|                                  |                                  |
|cseg segment                      |extern tagf:far                    |
|extern tagn:near                  |csegb segment                      |
|.                                  |.                                  |
|.                                  |.                                  |
|.                                  |.                                  |
|jmp tagn                          |jmp tagf                          |
|cseg ends                          |csegb ends                        |
\-----------------------------------------------------------------------/</pre>
<br />
 
[[[00716.htm|prev]]][[[00718.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EXTERNDEF (Declare Global Identifier) ===
 
The '''EXTERNDEF'''directive combines the functionality of the [[00716.htm|EXTERN/EXTRN]]and [[00720.htm|PUBLIC]]directives. It provides a uniform way to declare global symbols that are to be shared across multiple modules.
 
'''Syntax'''
 
<br />
 
<pre>EXTERNDEF  [ Language - Name ]  Name : Type  [ ,  . . . ] </pre>
Where ''Type''is one of:
 
�'''ABS''' <br />�[[00250.htm|''Type-Declaration'']]
 
'''Remarks'''
 
A symbol declared with '''EXTERNDEF'''is treated as [[00720.htm|PUBLIC]]if a definition for the symbol is encountered during the assembly, otherwise the symbol is assumed to be defined in another module and is treated as if it were declared with the [[00716.htm|EXTERN/EXTRN]]directive.
 
'''Example'''
 
The following example shows how a declaration for the '''ReturnCode'''symbol can be shared between two modules (Main.asm and FileErr.asm) by way of a common header file (ErrNum.inc): <br />
 
<pre>;  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;  ErrNum . inc
 
RETCODE _ T  typedef  DWORD
 
RC _ NoError        equ  0
RC _ FileNotFound  equ  1
RC _ SystemError    equ  3
 
EXTERNDEF  ReturnCode : RETCODE _ T      ;  declaration
 
 
;  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;  FileErr . asm
. 386
. MODEL  FLAT
INCLUDE  ErrNum . inc                  ;  bring  in  error  number  definitions
                                      ;  and  declaration  for  ReturnCode
 
. CODE
;  Tell  the  user  about  the  file  error ,
;  then  make  sure  the  program  has  a  non - zero  exit  status
FileError  proc
          . . .
          mov  ReturnCode ,  RC _ FileNotFound
          ret
FileError  endp
          end
 
 
;  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;  Main . asm
. 386
. MODEL  FLAT
INCLUDE  ErrNum . inc                  ;  bring  in  error  number  definitions
                                      ;  and  declaration  for  ReturnCode
EXTERNDEF  FileError : PROC            ;  This  could  be  in  a  common  header  too
 
. DATA
ReturnCode  RETCODE _ T  RC _ NoError    ;  actual  definition  of  ReturnCode
 
. CODE
Main  proc
      . . .
      . . .
      call  FileError            ;  hypothetical  error  condition
      . . .
      . . .
      mov  eax ,  ReturnCode      ;  load  the  exit  status
      call  Exit                  ;  and  shutdown  the  program
Main  endp
      end  Main
</pre>
<br />
 
[[[00717.htm|prev]]][[[00719.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== INCLUDELIB (Pass Library Name to Linker through Object File) ===
 
The '''INCLUDELIB'''directive is used to inform the linker that a library file of a given name is to be used when attempting to resolve external references declared by this module.
 
'''Syntax'''
 
<br />
 
<pre>INCLUDELIB  FileName </pre>
'''Remarks'''
 
The [[00652.htm|''FileName'']]argument is parsed as a contiguous string of arbitrary characters, and should constitute a file name that is valid in the context where it will be used. The [[00652.htm|''FileName'']]should be coded as a &lt;''text-literal''&gt; if it is to contain embedded spaces or other special characters.
 
The assembler emits a special record into the object file which contains the string of characters given by the [[00652.htm|''FileName'']]entry. This record instructs the linker to include the named library file in its list of libraries to be searched during the process of resolving external references. The assembler attaches no other meaning to the object file record, and it is up to the linker to interpret the file name for any special meaning (such as search path information, file name extension, and so on).
 
Use of this directive avoids the need to explicitly reference the library name in a linker invocation parameter, and helps to avoid the problems that can arise when such parameters are specified incorrectly.
 
'''Example'''
 
<br />
 
<pre>INCLUDELIB  OS2386 . LIB </pre>
<br />
 
[[[00718.htm|prev]]][[[00720.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== NAME (Specify Module Name) ===
 
The '''NAME'''directive assigns a module a name.
 
'''Syntax'''
 
<br />
 
<pre>NAME  module - name </pre>
'''Remarks'''
 
The '''NAME'''directive is ignored; it is provided for backward compatibility with other assemblers. <br />
 
[[[00719.htm|prev]]][[[00721.htm|next]]][[[00713.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== PUBLIC (Make Symbol Visible to Other Modules) ===
 
The '''PUBLIC'''directive makes defined symbols available to other programs that are to be linked. The information referred to by the '''PUBLIC'''directive is passed to the linker.
 
'''Syntax'''
 
<br />
 
<pre>PUBLIC  [ Language - Name ]  Identifier [ , . . . ] </pre>
'''Remarks'''
 
[[00149.htm|''Identifier'']]can be a variable or a label (including '''PROC'''labels). Register names and any symbols defined by '''EQU'''or = to floating-point numbers or integers larger than 4 bytes are incorrect entries.
 
'''Example'''
 
<br />
 
<pre>        PUBLIC    GETINFO    ; Make  GETINFO  visible  to  linker
GETINFO  PROC      FAR
        PUSH      BP          ; Save  caller ' s  register
        MOV        BP , SP      ; Get  address  of  parameters
                              ; BODY  OF  SUBROUTINE
        POP        BP          ; restore  caller ' s  register
        RET                  ; return  to  caller
GETINFO  ENDP </pre>
<br />
 
[[[00720.htm|prev]]][[[00722.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Listing Control ===
 
ALP creates an assembler listing of your source file whenever you use a related source code directive or specify the [[00050.htm|+Fl]]option on the ALP command line.
 
The assembler listing contains:
 
�Cumulative Listing Line Number <br />�Individual Source File Line Number <br />�Macro Expansion Line Number <br />�Macro Definition Line Number <br />�Macro Expansion Indentation Level <br />�Macro Expansion Nesting Level <br />�Include File Nesting Level <br />�Conditional Assembly Nesting Level <br />�True or False Conditional Flag <br />�Location Counter Offset Value <br />�Generated Machine Code Data <br />�Source Line Data <br />
 
If requested (via the [[00082.htm|+Ls]]command line option) a symbol table listing is produced that shows the names and values of all of the user-defined identifiers created during the assembly. The values of certain predefined identifiers are also show in the symbol table listing.
 
The symbol table listing is divided into the following categories:
 
�Macro Names <br />�Text Equate Names <br />�Structures/Union Type Names <br />�Orphaned Structure Fields <br />�Record Type Names <br />�Typedef Type Names <br />�Group Names <br />�Segment Names <br />�Numeric Equate Names <br />�Code Label Names <br />�Procedure Names <br />�Variable Names <br />
 
ALP places the symbol table listing at the end of the listing output. ALP lists only the types of symbols encountered in the program. For example, if your program does not define any macros, the '''Macro Names'''section is omitted from the listing output.
 
This section describes the following listing control directives:
 
%BIN <br />.CREF <br />.LALL <br />.LFCOND <br />.LIST <br />.LISTALL <br />.LISTIF <br />.LISTMACRO <br />.LISTMACROALL <br />.NOCREF <br />.NOLIST <br />.NOLISTIF <br />.NOLISTMACRO <br />PAGE <br />.SALL <br />.SFCOND <br />SUBTITLE <br />SUBTTL <br />.TFCOND <br />TITLE <br />.XALL <br />.XCREF <br />.XLIST <br />
 
[[[00721.htm|prev]]][[[00723.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== %BIN (Set Listing Width for Object Code Field) ===
 
Sets the width of the object code field in the listing file to ''size''columns .
 
'''Syntax'''
 
<br />
 
<pre>% BIN  size </pre>
<br />
 
[[[00722.htm|prev]]][[[00724.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .CREF/.XCREF (Control Symbol Cross Referencing) ===
 
The output of the cross-reference information is controlled by these directives. The default condition is the '''.CREF'''directive. When the assembler finds a '''.XCREF'''directive, cross-reference information results in no output until the assembler finds
 
'''Note:'''The assembler does not produce cross-referencing information. These directives are provided for source file compatibility with other assemblers .
 
 
 
'''Syntax'''
 
<br />
 
<pre>. CREF
    or
. XCREF  [ [ operand  [ , . . . ] ] </pre>
'''Remarks'''
 
The '''.XCREF'''directive can have an optional operand consisting of a list of one or more variable names suppressed in the cross-reference listing. <br />
 
[[[00723.htm|prev]]][[[00725.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LFCOND (List False Conditionals) ===
 
You use the '''.LFCOND'''(List False Conditionals) directive to list conditional blocks that are evaluated as false.
 
'''Syntax'''
 
<br />
 
<pre>. LFCOND </pre>
'''Remarks'''
 
Equivalent to the '''.LISTIF'''directive.
 
'''.LFCOND'''does not have an operand. You can end this state either by issuing '''.TFCOND''', which reverts to the default state concerning listing of false conditionals (but with the default state redefined as being in the opposite state,) or by issuing the '''.SFCOND''', which suppresses the listing of false conditionals.
 
The assembler does not print false conditionals within macros when '''.LALL'''is set. <br />
 
[[[00724.htm|prev]]][[[00726.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LIST/.XLIST (Control Listing File Output) ===
 
These two directives control output to the listing file.
 
'''Syntax'''
 
<br />
 
<pre>. LIST
    or
. XLIST </pre>
'''Remarks'''
 
If a listing is not being created, these directives have no effect. The '''. LIST'''is the default condition. When the assembler finds an '''.XLIST''', the assembler does not list the source and the object code until it finds a '''. LIST'''directive. <br />
 
[[[00725.htm|prev]]][[[00727.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LISTALL (List All Statements) ===
 
Starts the listing of all statements.
 
'''Syntax'''
 
<br />
 
<pre>. LISTALL </pre>
'''Remarks'''
 
Equivalent to the combination of '''.LIST''', '''.LISTIF''', and '''.LISTMACROALL'''. <br />
 
[[[00726.htm|prev]]][[[00728.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LISTIF (List False Conditionals) ===
 
Starts the listing of all statements, including those in false conditional blocks.
 
'''Syntax'''
 
<br />
 
<pre>. LISTIF </pre>
'''Remarks'''
 
Equivalent to the combination of '''.LIST''', '''.LISTIF''', and '''.LISTMACROALL'''. <br />
 
[[[00727.htm|prev]]][[[00729.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LISTMACRO/.XALL (List Code and Data Statements in Macros) ===
 
Starts listing of only those statements that generate code or data when processing macro expansions.
 
'''Syntax'''
 
<br />
 
<pre>. LISTMACRO
    or
. XALL </pre>
'''Remarks'''
 
ALP does not support this mode; it is provided for compatibility with other assemblers. <br />
 
[[[00728.htm|prev]]][[[00730.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .LISTMACROALL/.LALL (List All Statements in Macros) ===
 
Starts listing of all statements when processing macros expansions.
 
'''Syntax'''
 
<br />
 
<pre>. LISTMACROALL
    or
. LALL </pre>
<br />
 
[[[00729.htm|prev]]][[[00731.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .NOCREF (Suppress Symbol Cross Referencing) ===
 
Suppresses the listing of symbols in the symbol table and cross-referencing output.
 
'''Note:'''The assembler does not produce cross-referencing information. This directive is provided for source file compatibility with other assemblers.
 
 
 
'''Syntax'''
 
<br />
 
<pre>. NOCREF  [ name [ , name ] . . . ] </pre>
'''Remarks'''
 
If names are specified, only the given names are suppressed. Same as '''.XCREF''' . <br />
 
[[[00730.htm|prev]]][[[00732.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .NOLIST (Suppress List Output) ===
 
Suppresses program listing.
 
'''Syntax'''
 
<br />
 
<pre>. NOLIST </pre>
'''Remarks'''
 
Same as '''.XLIST'''. <br />
 
[[[00731.htm|prev]]][[[00733.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .NOLISTIF (Do Not List False Conditionals) ===
 
Suppresses listing of conditional blocks whose condition evaluates to false (0).
 
'''Syntax'''
 
<br />
 
<pre>. NOLISTIF </pre>
'''Remarks'''
 
This is the default. Same as '''.SFCOND'''. <br />
 
[[[00732.htm|prev]]][[[00734.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .NOLISTMACRO (Do Not List Macro Expansions) ===
 
Suppresses listing of macro expansion.
 
'''Syntax'''
 
<br />
 
<pre>. NOLISTMACRO </pre>
'''Remarks'''
 
Same as '''.SALL'''.
 
This is the default setting for ALP. <br />
 
[[[00733.htm|prev]]][[[00735.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== PAGE (Control Listing Page Length and Width) ===
 
The '''PAGE''' directive controls the length and width of each listing page. Place the '''PAGE'''directive in the source file to control the format of the listing file produced during assembly.
 
'''Syntax'''
 
<br />
 
<pre>PAGE  [ operand - 1 ] [ , operand - 2 ]
    or
PAGE  + </pre>
'''Remarks'''
 
Using '''PAGE'''+ or the '''PAGE'''directive without an operand entries causes the printer to go to the top of the page and increases the page number by 1. The assembler normally takes this action only when a page is full.
 
The ''operand-1''entry specifies the actual number of lines that can be physically printed on the page; the default value is 66.
 
Use the ''operand-2''entry to control the width of the page. The page width without a specified number is 132.
 
'''Note:'''The '''PAGE'''directive does not set the printer to the desired line width. For proper formatting of the listing, initialize the printer to operate at a corresponding line width before printing the listing file. <br />
 
[[[00734.htm|prev]]][[[00736.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== SUBTITLE/SUBTTL (Specify Listing Page Subtitle) ===
 
Defines the subtitle displayed in the user area of each page in the listing output.
 
'''Syntax'''
 
<br />
 
<pre>SUBTITLE  text
    or
SUBTTL  text </pre>
<br />
 
[[[00735.htm|prev]]][[[00737.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .TFCOND (Toggle Listing of False Conditionals) ===
 
Toggles listing of false conditional blocks.
 
'''Syntax'''
 
<br />
 
<pre>. TFCOND </pre>
<br />
 
[[[00736.htm|prev]]][[[00738.htm|next]]][[[00721.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== TITLE (Specify Listing Page Title) ===
 
Defines the title displayed in the user area of each page in the listing output.
 
'''Syntax'''
 
<br />
 
<pre>TITLE  text </pre>
<br />
 
[[[00737.htm|prev]]][[[00739.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Procedure Control ===
 
Procedure control directives allow you to organize your code into procedures. The '''PROC'''and '''ENDP'''directives mark the beginning and end of a procedure. Also, '''PROC'''can automatically:
 
�Preserve higher register values that should not change but that the procedure might otherwise alter <br />�Set up a local stack pointer, so that you can access parameters and local variables placed on the stack <br />�Adjust the stack when the procedure ends <br />
 
This section describes the following procedure control directives:
 
'''PROC''' <br />'''LOCAL''' <br />'''ENDP''' <br />
 
[[[00738.htm|prev]]][[[00740.htm|next]]][[[00738.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== PROC (Identify Code Procedure) ===
 
The '''PROC'''directive identifies a block of code. By dividing the code into blocks, each of which performs a distinct function, you can clarify the overall function of the complete module.
 
The '''PROC'''directive also identifies the procedure ''distance''to help insure that the assembler generates the appropriate instructions for calling and returning from the procedure while maintaining the integrity of the run- time stack.
 
'''Syntax'''
 
<br />
 
<pre>Procedure - Name  PROC  [ Attributes ]  [ Register - List ]  [ Parameter - List ]
    .
    .
    .
RET  [ Constant ]
    .
    .
    .
Procedure - Name  ENDP </pre>
 
 
Refer to the following sections for descriptions of the optional arguments to the '''PROC'''directive:
 
�[[00740.htm|''Attributes'']] <br />�[[00741.htm|''Register-List'']] <br />�[[00742.htm|''Parameter-List'']]
 
'''Remarks'''
 
You can execute the block of code identified by the '''PROC'''directive in-line, jump to it, or start it with a '''CALL'''instruction. If the '''PROC'''is called from code that has another '''ASSUME CS'''value, you must use the appropriate '''FAR''', '''FAR16''', or '''FAR32'''''distance attribute''.
 
The '''NEAR'''attribute causes any '''RET'''instruction coded within the procedure to be an intra-segment return that pops a return '''''offset''from the stack. You can call a '''NEAR'''subroutine only from the same segment. However, the '''FAR''' attribute causes '''RET'''to be an inter-segment return that pops both a return '''''offset''and a '''''segment base''from the stack. You can call a '''FAR'''subroutine from any segment; a '''FAR'''subroutine is usually called from a segment other than the one containing the subroutine.'''''''''
 
'''Example'''
 
In this example, the '''Near_Name'''subroutine is called by the '''Far_Name''' subroutine. <br />
 
<pre>          PUBLIC    Far _ Name
Far _ Name    PROC      FAR
          CALL  Near _ Name
          RET                  ; Pops  return  offset  and  seg  base  value
Far _ Name    ENDP
 
          PUBLIC    Near _ Name
Near _ Name  PROC      NEAR
          .
          .
          .
          RET                  ; pops  only  return  offset
Near _ Name  ENDP </pre>
You can call the '''Near_Name'''subroutine directly from a '''NEAR'''segment by using : <br />
 
<pre>CALL  Near _ Name </pre>
A '''FAR'''segment can indirectly call the second subroutine by first calling the '''Far_Name'''subroutine with: <br />
 
<pre>CALL  Far _ Name </pre>
A '''CALL'''to a forward-referenced symbol assumes the symbol is '''NEAR'''. If that symbol is '''FAR''', the '''CALL'''must have an override, for example: <br />
 
<pre>CALL  FAR  PTR  Forward _ Reference </pre>
<br />
 
[[[00739.htm|prev]]][[[00741.htm|next]]][[[00739.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Attributes ===
 
The optional fields in the ''Attributes''argument control how the procedure is defined.
 
'''Syntax'''
 
<br />
 
<pre>[ Distance ]  [ Language ]  [ Visibility ] </pre>
'''Remarks'''
 
The various ''Attribute''fields are defined as follows:
 
'''''Distance''Determines the type of '''CALL'''instruction that should be used to invoke the procedure, and the type of '''RET'''instruction generated by the assembler. The default is '''NEAR'''if no [[00775.htm|.MODEL]]directive has been specified, or if the model has been set to '''TINY''', '''SMALL''', '''COMPACT''', or '''FLAT'''. The default is '''FAR'''if the model has been set to '''LARGE''', '''MEDIUM''', or '''HUGE'''. If the programmer is using segments with mixed address sizes ('''USE16'''and '''USE32''') on a 32-bit processor, then the '''NEAR16''', '''FAR16''', '''NEAR32''', and '''FAR32'''keywords may also be used.'''
 
'''''Language''Determines the calling convention used by the procedure, and the naming convention used when writing the procedure name to the object file. The calling convention defines the layout of the stack frame upon entry to the procedure and how the stack frame is destroyed upon procedure exit. See the section on [[00163.htm|''LabelName'']]''s''for more information on language naming conventions.'''
 
With the '''BASIC''', '''FORTRAN''', and '''PASCAL'''calling conventions, the called procedure expects arguments to be pushed on the stack from left to right, causing the rightmost parameter to be at the lowest stack address and closest in proximity to the ''frame pointer''(the BP or EBP register). With this arrangement, the called procedure always knows the exact amount of stack space used by the parameters, and is responsible for removing them from the stack with a '''RET''''''''Constant''instruction when the procedure exits. Such procedures are unable to accept a variable number of arguments.'''
 
With the '''C''', '''STDCALL''', '''SYSCALL''', and '''OPTLINK'''calling conventions, the called procedure expects arguments to be pushed on the stack from right to left, causing the leftmost parameter to be at the lowest stack address and closest in proximity to the ''frame pointer''(the BP or EBP register). With this arrangement, the calling procedure is free to push additional arguments on the stack, and is responsible for restoring the stack after the called procedure returns ('''STDCALL'''requires the called procedure to restore the stack if a fixed number of arguments is being passed).
 
With the '''OPTLINK'''32-bit calling convention (as defined by the IBM VisualAge C/C++ Compiler environment), up to three parameters will be passed in machine registers to the called procedure, provided they not larger than a DWORD in size. The EAX, EDX, and ECX registers (respectively) are used for this purpose. Stack space for the parameters is still allocated, but the parameter values are not actually copied onto the stack. Refer to the documentation for the IBM VisualAge C++ compiler for more information on the '''OPTLINK'''calling convention.
 
'''''Visibility''Determines if the procedure name is written to the object file as a global identifier, allowing it to be referenced by other modules. The allowable values are '''PRIVATE''', '''PUBLIC''', and '''EXPORT'''. If operating in [[00105.htm|M510]] mode and no [[00775.htm|.MODEL]]directive with a [[00131.htm|''Language-Name'']]has been specified, then the default visibility is '''PRIVATE'''. In all other situations, the default visibility is '''PUBLIC'''unless the default has been overridden by an [[00793.htm|OPTION LANGUAGE]]directive.'''
 
When the '''PRIVATE'''keyword is used, the procedure name is visible only within the defining module at assembly-time. When the visibility is '''PUBLIC''', the procedure name is made visible to other modules at link-time. The same is true of '''EXPORT'''visibility, but in this case the assembler emits a special record into the object file that causes the linker to also make the symbol visible as an exported entry point in the executable module , allowing it be called by other modules at program run-time. <br />
 
[[[00740.htm|prev]]][[[00742.htm|next]]][[[00739.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Register List ===
 
The optional ''Register-List''defines those registers used in the body of the procedure that must be preserved on behalf of the caller. The assembler generates code to save these registers on the stack when the procedure is entered, and to restore them when the procedure exits.
 
'''Syntax'''
 
<br />
 
<pre>USES  Register  [  Register . . . ] </pre>
'''''Register:'' <br />[[00122.htm|''16-Bit-Register'']] <br />[[00122.htm|''32-Bit-Register'']] <br />[[00122.htm|''Segment-Register'']] <br />'''
 
'''Remarks'''
 
When more than one register is specified, do not use commas to separate the register keywords; use blanks or tabs instead. <br />
 
[[[00741.htm|prev]]][[[00743.htm|next]]][[[00739.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Parameter List ===
 
The optional ''Parameter-List''defines the parameters that the caller passes to the procedure on the run-time stack.
 
'''Syntax'''
 
<br />
 
<pre>[ ,  [ LineBreak ] ]  Parm - List </pre>
'''''Parm-List:'' <br />''Parm-Spec''[, [''LineBreak''] ''Parm-Spec''...] <br />'''
 
'''''Parm-Spec:'' <br />''Parameter-Name''[:''Type''] <br />'''
 
The introductory comma in front of the ''Parm-List''is only required if a ''LineBreak''is used to put the first ''Parm-Spec''on the line following the '''PROC''' directive.
 
The optional ''LineBreak''entry allows you to end a ''Parm-Spec''entry with a comma, enter an optional [[00657.htm|''EndOfLine-Comment'']]followed by a physical ''NewLine'' character, then continue the ''Parm-List''on the next line.
 
'''Remarks'''
 
Each ''Parameter-Name''is defined as a [[00156.htm|''Numeric-EquateName'']]that is visible only from within the body of the procedure. The value assigned to the parameter name is an expression that defines the parameter type and its location on the stack relative to the value of the ''frame pointer''(the BP or EBP register). The assembler automatically calculates the correct offset value based upon the size of the parameter type.
 
The ''Type''field is specified as a [[00250.htm|''Type-Declaration'']]and defines the data type associated with the ''Parameter-Name''. If this field is omitted, the data type defaults to '''WORD'''if the procedure is defined within a '''USE16'''segment, and '''DWORD'''if the procedure is defined within a '''USE32'''segment.
 
The programmer can read from and store into the locations defined by the ''Parm-Spec''entries as though they were regular named variables, but if the parameter names are to be combined in indexed expressions with other registers, the normal rules for specifying '''BP'''- and '''EBP'''-relative expressions must be followed.
 
'''Example'''
 
This example defines a '''ReadBuffer'''procedure to accept four arguments passed on the stack. <br />
 
<pre>        . 386                          ;  Assemble  for  32 - bit  processors
        . model  flat , syscall        ;  OS / 2  programming  model / calling  convention
 
        EXTERN  DosRead : PROC        ;  OS / 2  DosRead ( )  API
        INCLUDELIB  os2386 . lib      ;  This  lets  us  link  to  the  API
 
        . code                        ;  Open  the  code  segment
 
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;  Call  operating  system  to  read  input  into  a  buffer
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
ReadBuffer  PROC ,                    ;  need  comma  to  continue  the  PROC  statement
                hFile : dword ,          ;  parm  1 :  Read  handle
                pBuffer : ptr  byte ,    ;  parm  2 :  Address  of  input  buffer
                cbRead : dword ,        ;  parm  3 :  Size  of  input  buffer
                pulActual : ptr  dword  ;  parm  4 :  Address  of  byte  count  from  read
 
        ;  set  up  to  call  the  OS / 2  DosRead  entry  point
 
        PUSH    pulActual              ;  arg  4
        PUSH    cbRead                ;  arg  3
        PUSH    pBuffer                ;  arg  2
        PUSH    hFile                  ;  arg  1
        CALL    DosRead                ;  Invoke  syscall  ( SYSTEM )  function
        ADD    ESP , DWORD  *  4        ;  Remove  the  four  parameters  we  pushed
                                      ;    onto  the  stack  for  the  DosRead  call
        RET
ReadBuffer      ENDP </pre>
<br />
 
[[[00742.htm|prev]]][[[00744.htm|next]]][[[00738.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== LOCAL (Define Local Procedure Variables) ===
 
The '''LOCAL'''directive defines local stack variables from within a code procedure.
 
'''Syntax'''
 
<br />
 
<pre>LOCAL  Local - Spec  [ ,  [ LineBreak ]  Local - Spec  . . . ] </pre>
'''''Local-Spec:'' <br />''Local-Name''[:[[00250.htm|''Type-Declaration'']]] <br />''Local-Name[Count]''[:[[00250.htm|''Type-Declaration'']]] <br />'''
 
The optional ''LineBreak''entry allows you to end a ''Local-Spec''entry with a comma, enter an optional [[00657.htm|''EndOfLine-Comment'']]followed by a physical ''NewLine'' character, then continue with a new ''Local-Spec''on the next line.
 
'''Remarks'''
 
The '''LOCAL'''assembler directive can only appear within the body of a procedure. If used, the '''LOCAL'''directive(s) must immediately follow the '''PROC'''statement that encloses them, and they must appear before any instructions, code labels, or directives that modify the location counter. Multiple '''LOCAL'''directives may appear in succession.
 
Each ''Local-Name''is defined as a [[00156.htm|''Numeric-EquateName'']]that is visible only from within the body of the procedure. The value assigned to the variable name is an expression that defines the type of the variable and its location on the stack relative to the value of the ''frame pointer''(the BP or EBP register). The assembler reserves space on the stack for each local variable and automatically calculates their locations. After all ''Local- Spec''entries have been processed, the assembler allocates the space by generating instructions to adjust the stack pointer. The assembler also generates instructions to restore the state of the stack and frame pointers when the procedure exits.
 
The optional ''[Count]''entry can be used to indicate that the variable is a simple &quot;array&quot; of values, where ''Count''is a constant expression. If used, the square brackets surrounding the ''Count''must be specified. Use of this notation is discouraged however, because it does not associate a &quot;true array&quot; data type with the variable, and cannot be viewed as such from within a symbolic debugger. ALP allows the variable to be associated with a &quot;true array&quot; data type through use of the native [[00250.htm|''Type-Declaration'']]syntax.
 
The [[00250.htm|''Type-Declaration'']]field specifies the data type to be associated with the ''Local-Name''. If this field is omitted, the data type defaults to '''WORD''' if the procedure is defined within a '''USE16'''segment, and '''DWORD'''if the procedure is defined within a '''USE32'''segment.
 
'''Example'''<br />
 
<pre>;  bootdrv . asm  :  Returns  value  of  OS / 2  boot  drive  as  exit  code
;  assemble  as  :  alp  + Od  bootdrv . asm
;  link  as      :  link386  / de  bootdrv ;
 
        . 386                            ;  Assemble  for  32 - bit  processors
        . model  flat , syscall          ;  OS / 2  flat  model / calling  convention
        . stack  4096
 
        EXTERN  DosExit : PROC          ;  OS / 2  DosExit ( )  API
        EXTERN  DosQuerySysInfo : PROC  ;  OS / 2  DosQuerySysInfo ( )  API
        INCLUDELIB  os2386 . lib        ;  link  with  these  routines
 
;  These  are  values  taken  from  OS / 2  API  headers .    See  the  OS / 2  Toolkit
;  Control  Program  Programming  Guide  and  Reference  for  more  information .
 
EXIT _ PROCESS      EQU    1                ;  for  DosExit
QSV _ BOOT _ DRIVE    EQU    5                ;  For  DosQuerySysInfo
 
ULONG    TYPEDEF  DWORD                  ;  use  OS / 2  type  convention
 
        . code                          ;  open  code  segment
 
main      PROC
        LOCAL  BootDrive : ULONG        ;  place  to  put  value  of  boot  drive
 
        ;  Push  parameters  to  DosQuerySysInfo  onto  the  stack
 
        PUSH    sizeof  BootDrive        ;  arg  4 :  size  of  output  buffer
        LEA    EAX , BootDrive          ;  arg  3 :  Address  of  buffer
        PUSH    EAX
        PUSH    QSV _ BOOT _ DRIVE          ;  arg  2 :  last  ordinal  value  to  return
        PUSH    QSV _ BOOT _ DRIVE          ;  arg  1 :  first  ordinal ,  same  as  last
        CALL    DosQuerySysInfo        ;  invoke  API
        ADD    ESP , DWORD  *  4          ;  remove  the  parameters  from  the  stack
 
        CMP    EAX , 0                    ;  Did  the  API  succeed ?
        MOV    EAX , 0                    ;    if  not ,  use  zero  as  a  return  code
        JNZ    SomeKindOfError        ;    and  skip  around  to  the  exit  logic
        MOV    EAX , BootDrive          ;  else ,  return  the  boot  drive  value
SomeKindOfError :
        push    EAX                      ;  exit  code
        push    EXIT _ PROCESS            ;  terminates  all  threads
        call    DosExit                  ;  exit  to  calling  process
        RET                            ;  never  executed
main      ENDP
 
        END    main </pre>
<br />
 
[[[00743.htm|prev]]][[[00745.htm|next]]][[[00738.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ENDP (Close a Procedure Definition Block) ===
 
Every procedure block opened with the '''PROC'''directive must be ended with the '''ENDP'''directive.
 
'''Syntax'''
 
<br />
 
<pre>procedure - name  ENDP </pre>
'''Remarks'''
 
If the '''ENDP'''directive is not used with the '''PROC'''directive, an error occurs. An unmatched '''ENDP'''also causes an error.
 
 
 
'''Note:'''See the '''PROC'''directive in this chapter for more detail and examples of '''ENDP'''use.
 
'''Example'''
 
<br />
 
<pre>PUSH      AX                  ;  Push  third  parameter
PUSH      BX                  ;  Push  second  parameter
PUSH      CX                  ;  Push  first  parameter
CALL      ADDUP              ;  Call  the  procedure
ADD        SP , 6                ;  Bypass  the  pushed  parameters
.
.
.
ADDUP      PROC    NEAR        ;  Return  address  for  near  call
                            ;  takes  two  bytes
          PUSH    BP          ;  Save  base  pointer  -  takes  two  more
                            ;  so  parameters  start  at  4th  byte
          MOV      BP , SP      ;  Load  stack  into  base  pointer
          MOV      AX , [ BP + 4 ]  ;  Get  first  parameter
                            ;  4th  byte  above  pointer
          ADD      AX , [ BP + 6 ]  ;  Get  second  parameter
                            ;  6th  byte  above  pointer
          ADD      AX , [ BP + 8 ]  ;  Get  third  parameter
                            ;  8th  byte  above  pointer
          POP      BP          ;  Restore  base
          RET                ;  Return
ADDUP      ENDP </pre>
In this example, three numbers are passed as parameters for the procedure '''ADDUP'''. Parameters are often passed to procedures by pushing them before the call so that the procedure can read them off the stack. <br />
 
[[[00744.htm|prev]]][[[00746.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Processor Control ===
 
ALP provides a set of directives for selecting processors and coprocessors. Once you select a processor, you must only use the instruction set available for that processor. The default is the 8086 processor. If you always want your code to run on this processor, you need not add any processor directives.
 
This section describes the following processor control directives:
 
.8086 <br />.8087 <br />.186 <br />.286 <br />.286P <br />.287 <br />.386 <br />.386P <br />.387 <br />.486 <br />.486P <br />.586 <br />.586P <br />.686 <br />.686P <br />.MMX <br />.NOMMX <br />
 
[[[00745.htm|prev]]][[[00747.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .8086 (Select 8086 Processor Instruction Set) ===
 
The '''.8086'''directive tells the assembler to recognize and assemble 8086 instructions. This directive assembles only 8086 and 8088 instructions (the 8088 instructions are identical to the 8086 instructions). ALP assembles 8086 instructions by default.
 
'''Syntax'''
 
<br />
 
<pre>. 8086 </pre>
'''Remarks'''
 
The '''.8086'''directive does not have an operand.
 
'''Note:'''The '''.8086'''directive does not end ALP 8087/80287 mode. <br />
 
[[[00746.htm|prev]]][[[00748.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .8087 (Select 8087 Coprocessor Instruction Set) ===
 
The '''.8087'''directive tells the assembler to recognize and assemble 8087 instructions and data formats. ALP assembles 8087 instructions by default.
 
'''Syntax'''
 
<br />
 
<pre>. 8087 </pre>
'''Remarks'''
 
The '''.8087'''directive does not have an operand. <br />
 
[[[00747.htm|prev]]][[[00749.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .186 (Select 80186 Processor Instruction Set) ===
 
The '''.186'''directive tells the assembler to recognize and assemble 8086 or 8088 instructions and the additional instructions for the 80186 microprocessor.
 
'''Syntax'''
 
<br />
 
<pre>. 186 </pre>
'''Remarks'''
 
The '''.186'''directive does not have an operand. Use it only for programs that run on an 80186 microprocessor. <br />
 
[[[00748.htm|prev]]][[[00750.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .286 (Select 80286 Processor Instruction Set) ===
 
Enables assembly of nonprivileged instructions for the 80286 processor. Disables assembly of instructions introduced with later processors. Also enables 80287 instructions.
 
'''Syntax'''<br />
 
<pre>. 286 </pre>
<br />
 
[[[00749.htm|prev]]][[[00751.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .286P (Select 80286 Processor Protected Mode Instruction Set) ===
 
The '''.286P'''directive tells the assembler to recognize and assemble the protected instructions of the 80286 in addition to the 8086, 8088, and nonprotected 80286 instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 286P </pre>
'''Remarks'''
 
The '''.286P'''directive does not have an operand. Use it only for programs run on an 80286 processor using both protected and nonprotected instructions. <br />
 
[[[00750.htm|prev]]][[[00752.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .287 (Select 80287 Coprocessor Instruction Set) ===
 
The '''.287'''directive tells the assembler to recognize and assemble instructions for the 80287 floating point math coprocessor. The 80287 instruction set consists of all 8087 instructions, plus three additional instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 287 </pre>
'''Remarks'''
 
The '''.287'''directive does not have an operand. Use it only for programs that have 80287 floating point instructions and run on an 80287 math coprocessor . <br />
 
[[[00751.htm|prev]]][[[00753.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .386 (Select 80386 Processor Instruction Set) ===
 
Enables assembly of nonprivileged instructions for the 80386 processor. Disables assembly of instructions introduced with later processors. Also enables 80387 instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 386 </pre>
<br />
 
[[[00752.htm|prev]]][[[00754.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .386P (Select 80386 Processor Protected Mode Instruction Set) ===
 
Enables assembly of all instructions (including privileged) for the 80386P processor. Disables assembly of instructions introduced with later processors. Also enables 80387 instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 386P </pre>
<br />
 
[[[00753.htm|prev]]][[[00755.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .387 (Select 80387 Coprocessor Instruction Set) ===
 
Enables assembly of instructions for the 80387 coprocessor.
 
'''Syntax'''
 
<br />
 
<pre>. 387 </pre>
<br />
 
[[[00754.htm|prev]]][[[00756.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .486 (Select 80486 Processor Instruction Set) ===
 
Enables assembly of instructions for the 80486 processor. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 486 </pre>
'''Remarks'''
 
The '''.486'''directive is not available in [[00105.htm|M510]]mode. <br />
 
[[[00755.htm|prev]]][[[00757.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .486P (Select 80486 Processor Protected Mode Instruction Set) ===
 
Enables assembly of all instructions (including privileged) for the 80486 processor. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 486P </pre>
'''Remarks'''
 
The '''.486P'''directive is not available in [[00105.htm|M510]]mode. <br />
 
[[[00756.htm|prev]]][[[00758.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .586 (Select Pentium/586 Processor Instruction Set) ===
 
Enables assembly of instructions for the Pentium processor family. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 586 </pre>
'''Remarks'''
 
The '''.586'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode. <br />
 
[[[00757.htm|prev]]][[[00759.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .586P (Select Pentium/586 Processor Protected Mode Instruction Set) ===
 
Enables assembly of all instructions (including privileged) for the Pentium processor family. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 586P </pre>
'''Remarks'''
 
The '''.586P'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode. <br />
 
[[[00758.htm|prev]]][[[00760.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .686 (Select Pentium Pro/686 Processor Instruction Set) ===
 
Enables assembly of instructions for the Pentium Pro processor family. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 686 </pre>
'''Remarks'''
 
The '''.686'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode. <br />
 
[[[00759.htm|prev]]][[[00761.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .686P (Select Pentium Pro/686 Processor Protected Mode Instruction Set) ===
 
Enables assembly of all instructions (including privileged) for the Pentium Pro processor family. Also enables 80387 (and later) floating point instructions.
 
'''Syntax'''
 
<br />
 
<pre>. 686P </pre>
'''Remarks'''
 
The '''.686P'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode. <br />
 
[[[00760.htm|prev]]][[[00762.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .MMX (Select MMX Processor Instruction Set Extensions) ===
 
Enables recognition of mnenomics for the MMX instruction set extensions.
 
'''Syntax'''
 
<br />
 
<pre>. MMX </pre>
'''Remarks'''
 
If 586 mnemonics (or later) are not already being recognized, the '''.MMX''' directive also causes an implicit '''.586'''directive to be executed.
 
Issuing any '''.486'''(or earlier) processor selection directive causes recognition of MMX mnemonics to be disabled.
 
If MMX mnemonics are being recognized, issuing a '''.586'''(or later) processor selection directive does not cause recognition of MMX mnemonics to be disabled. If this behavior is desired, use the '''.NOMMX'''directive.
 
The '''.MMX'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode. <br />
 
[[[00761.htm|prev]]][[[00763.htm|next]]][[[00745.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .NOMMX (Deselect MMX Processor Instruction Set Extensions) ===
 
Disables recognition of mnenomics for the MMX instruction set extensions.
 
'''Syntax'''
 
<br />
 
<pre>. NOMMX </pre>
'''Remarks'''
 
Does not affect recognition of instruction mnemonics for the currently selected primary processor; it only disables recognition of the MMX mnemonics.
 
The '''.NOMMX'''directive is not available in [[00105.htm|M510]]mode or [[00105.htm|M600]]mode.
 
'''Example'''<br />
 
<pre>;  Top  of  file  -  no  processor  currently  selected
. MMX            ;  enables  both  MMX  and  586  mnemonics
. NOMMX          ;  586  mnemonics  still  enabled
. 686            ;  686  mnemonics  now  being  recognized
. MMX            ;  686  and  MMX  mnemonics  now  being  recognized
. NOMMX          ;  686  mnemonics  still  enabled </pre>
<br />
 
[[[00762.htm|prev]]][[[00764.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Segments ===
 
A segment is a collection of instructions or data whose addresses are all relative to the same segment register. The code in your assembler language program defines and organizes segments.
 
You can define segments by using segment directives or full segment definitions.
 
This section describes the following directives used to create and manage segments:
 
ALIGN <br />.CODE <br />.CONST <br />.DATA <br />.DATA? <br />DOSSEG <br />.DOSSEG <br />ENDS <br />EVEN <br />.FARDATA <br />.FARDATA? <br />GROUP <br />.MODEL <br />ORG <br />SEGMENT <br />.SEQ <br />.STACK <br />
 
[[[00763.htm|prev]]][[[00765.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ALIGN (Align Code or Data Item) ===
 
Advances the current location counter to the next byte boundary that is a multiple of [[00255.htm|''Expression'']].
 
'''Syntax'''
 
<br />
 
<pre>ALIGN  Expression </pre>
'''Example'''
 
To align to a 2-byte boundary: <br />
 
<pre>ALIGN  2 </pre>
To align to a 4-byte boundary: <br />
 
<pre>ALIGN  4 </pre>
<br />
 
[[[00764.htm|prev]]][[[00766.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .CODE (Opens Default or Named Code Segment) ===
 
Closes the currently opened segment (if any) and opens the default code segment or a segment with the name given by an optional ''SegmentName'' parameter. The '''.CODE'''directive may only be used if previous [[00775.htm|.MODEL]] directive has been processed.
 
'''Syntax'''
 
<br />
 
<pre>. CODE  [ SegmentName ] </pre>
'''Remarks'''
 
When the ''SegmentName''parameter is omitted from the '''.CODE'''directive, the assembler generates a default code segment whose name is determined by the memory model as follows:
 
'''Memory Model''''''Value for @code''' <br />TINY _TEXT <br />SMALL _TEXT <br />MEDIUM ''module''_TEXT <br />COMPACT_TEXT <br />LARGE ''module''_TEXT <br />HUGE ''module''_TEXT <br />FLAT CODE32
 
The ''module''entry is replaced with base file name of the top-level module being assembled.
 
When operating in [[00105.htm|M510]]mode, the ''SegmentName''parameter may only be specified for those memory models that allow multiple code segments (MEDIUM , LARGE, and HUGE), and the value of the [[00177.htm|@code]]symbol is not altered from the default. For other modes of operation, the ''SegmentName''parameter is allowed for any model other than TINY, and the [[00177.htm|@code]]symbol is updated to reflect the ''SegmentName''value. <br />
 
[[[00765.htm|prev]]][[[00767.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .CONST (Opens Default Constant Data Segment) ===
 
When used with '''.MODEL''', starts a constant data segment for initialized read- only data.
 
'''Syntax'''
 
<br />
 
<pre>. CONST </pre>
'''Remarks'''
 
The name of the segment is CONST32 in flat model, and CONST for all other models. <br />
 
[[[00766.htm|prev]]][[[00768.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .DATA (Opens Default Data Segment) ===
 
When used with '''.MODEL''', starts a near data segment for initialized data.
 
'''Syntax'''
 
<br />
 
<pre>. DATA </pre>
'''Remarks'''
 
The name of the segment is DATA32 in flat model, and _DATA for all other models. <br />
 
[[[00767.htm|prev]]][[[00769.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .DATA? (Opens Default Uninitialized Data Segment) ===
 
When used with '''.MODEL''', starts a near data segment for uninitialized data.
 
'''Syntax'''
 
<br />
 
<pre>. DATA ? </pre>
'''Remarks'''
 
The name of the segment is BSS32 in flat model, and _BSS for all other models. <br />
 
[[[00768.htm|prev]]][[[00770.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .DOSSEG/DOSSEG (Specify Standard DOS Segment Ordering) ===
 
Orders the segments according to the DOS segment convention: CODE first, then segments not in DGROUP, and then segments in DGROUP. The segments in DGROUP follow this order:
 
1.Segments not in BSS or STACK <br /> 2.BSS segments <br /> 3.STACK segments <br />
 
'''Syntax'''
 
<br />
 
<pre>. DOSSEG  ( preferred  form )
    or
DOSSEG </pre>
'''Remarks'''
 
'''.DOSSEG'''is the preferred form.
 
Use of this directive allows the linker to control the segment ordering according to conventions used in many high-level languages. <br />
 
[[[00769.htm|prev]]][[[00771.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ENDS (Close a Segment, Structure, or Union Declaration) ===
 
Closes a program segment opened with '''SEGMENT'''directive, or ends a structure or union definition opened with the '''STRUCT'''or '''UNION'''directives. Every '''SEGMENT''', '''STRUCT''', and '''UNION'''directive must end with a corresponding '''ENDS''' directive.
 
'''Syntax'''
 
<br />
 
<pre>Segment - Name  ENDS
    or
Structure - Name  ENDS
    or
Union - Name  ENDS </pre>
'''Remarks'''
 
If the '''ENDS'''directive is not used with the corresponding '''SEGMENT''', '''STRUCT''', or '''UNION'''directive, an error occurs. An unmatched '''ENDS'''also causes an error.
 
 
 
'''Note:'''See the [[00777.htm|SEGMENT]], [[00782.htm|STRUCT]], and [[00784.htm|UNION]]directives for more details and examples of the use of '''ENDS'''.
 
'''Example'''
 
<br />
 
<pre>CONST      SEGMENT      word  public  ' CONST '
SEG1      DW          ARRAY _ DATA
SEG2      DW          MESSAGE _ DATA
CONST      ENDS </pre>
<br />
 
[[[00770.htm|prev]]][[[00772.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EVEN (Align Code or Data Item on an Even Boundary) ===
 
The '''EVEN'''directive causes the program counter to go to an even boundary (an address that begins a word). This ensures that the code or data that follows is aligned on an even boundary.
 
'''Syntax'''
 
<br />
 
<pre>EVEN </pre>
'''Remarks'''
 
If the program counter is not already at an even boundary, '''EVEN'''causes the assembler to add a '''NOP'''(no operation) instruction so that the counter reaches an even boundary. An error message occurs if '''EVEN'''is used with a byte-aligned segment. If the program counter is already at an even boundary, '''EVEN'''does nothing.
 
'''Example'''
 
Before: PC points to 0019 hex (25 decimal).
 
<br />
 
<pre>EVEN </pre>
After: PC points to 001A hex (26 decimal). <br />
 
[[[00771.htm|prev]]][[[00773.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .FARDATA (Opens Default or Named Far Data Segment) ===
 
When used with '''.MODEL''', starts a far data segment for initialized data.
 
'''Syntax'''
 
<br />
 
<pre>. FARDATA  [ SegmentName ] </pre>
'''Remarks'''
 
If the ''SegmentName''parameter is not specified, the assembler sets it to FAR _DATA. <br />
 
[[[00772.htm|prev]]][[[00774.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .FARDATA? (Opens Default or Named Uninitialized Far Data Segment) ===
 
When used with '''.MODEL''', starts a far data segment for uninitialized data.
 
'''Syntax'''
 
<br />
 
<pre>. FARDATA ?  [ SegmentName ] </pre>
'''Remarks'''
 
If the ''SegmentName''parameter is not specified, the assembler sets it to FAR _BSS. <br />
 
[[[00773.htm|prev]]][[[00775.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== GROUP (Treat Multiple Segments as a Single Unit) ===
 
The '''GROUP'''directive associates a group ''Name''with one or more segments, and causes all labels and variables defined in the given segments to have addresses relative to the beginning of the group, rather than to the segments where they are defined.
 
'''Syntax'''
 
<br />
 
<pre>Name  GROUP  Segment - Name  [ , . . . ] </pre>
'''Remarks'''
 
Each ''Segment-Name''entry must be a unique segment name assigned by the [[00777.htm|SEGMENT]]directive. A ''Segment-Name''entry may be a forward reference to a subsequently declared segment name.
 
An additional occurrence of a given group ''Name''in a subsequent '''GROUP''' directive does not constitute a redefinition, but instead the effect is cumulative. The group ''Name''itself is declared the first time it appears in a '''GROUP'''directive, but the group definition is not complete until the end of the source module is reached. The final group definition is the cumulative list of all unique segments named in all occurrences of a '''GROUP''' directive for that group ''Name''.
 
Segments in a group need not be contiguous. Segments that do not belong to the group can be loaded between segments that do belong to the group. The only restriction is that for USE16 segments the distance (in bytes) between the first byte in the first segment of the group and the last byte in the last segment must not exceed 65535 bytes.
 
Group names can be used with the [[00788.htm|ASSUME]]directive and as an operand prefix with the segment override operation (:).
 
'''Example'''
 
The following example shows how to use the '''GROUP'''directive to combine segments:
 
'''In Module A:'''<br />
 
<pre>CGROUP    GROUP      XXX , YYY
XXX        SEGMENT
          ASSUME    CS : CGROUP
          .
          .
          .
XXX        ENDS
YYY        SEGMENT
          ASSUME    CS : CGROUP
          .
          .
          .
YYY        ENDS </pre>
'''In Module B:'''<br />
 
<pre>CGROUP    GROUP      ZZZ
ZZZ        SEGMENT
          ASSUME    CS : CGROUP
          .
          .
          .
ZZZ        ENDS </pre>
The next example shows how to set '''DS'''with the paragraph number of the group called '''DGROUP'''.
 
'''As immediate:'''<br />
 
<pre>MOV        AX , DGROUP
MOV        DS , AX </pre>
'''In assume:'''<br />
 
<pre>ASSUME      DS : DGROUP </pre>
'''As an operand prefix:'''<br />
 
<pre>MOV      BX , OFFSET  DGROUP : FOO
DW      FOO
DW      DGROUP : FOO </pre>
'''Note:'''
 
1.'''DW FOO'''returns the offset of the symbol within its segment.
 
2.'''DW DGROUP:FOO'''returns the offset of the symbol within the group.
 
The next example shows how you can use the '''GROUP'''directive to create a '''.COM''' file type. <br />
 
<pre>PAGE      , 132
TITLE    GRPCOM  -  Use  GROUP  to  create  a  DOS  . COM  file
; Use  the  DOS  EXE2BIN  utility  to  convert  GRPCOM . EXE  to  GRPCOM . COM .
 
CG        GROUP      CSEG , DSEG      ; ALL  SEGS  IN  ONE  GROUP
DISPLAY  MACRO      TEXT
LOCAL    MSG
DSEG      SEGMENT    BYTE  PUBLIC  ' DATA '
MSG      DB        TEXT , 13 , 10 , &quot; $ &quot;
DSEG      ENDS
; ; Macro  produces  partly  in  DSEG ,
; ; partly  in  CSEG
        MOV        AH , 9
        MOV        DX , OFFSET  CG :  MSG
; ; Note  use  of  group  name
; ; in  producing  offset
        INT  21H
        ENDM
DSEG      SEGMENT    BYTE  PUBLIC  ' DATA '
; Insert  local  constants  and  work  areas  here
DSEG      ENDS
CSEG      SEGMENT  BYTE  PUBLIC  ' CODE '
  ASSUME    CS : CG , DS : CG , SS : CG , ES : CG  ; SET  BY  LOADER
        ORG  100H  ; Skip  to  end  of  the  PSP
ENTPT    PROC      NEAR  ; COM  file  entry  at  0100H
      DISPLAY  &quot; USING  MORE  THAN  ONE  SEGMENT &quot;
      DISPLAY  &quot; YET  STILL  OBEYING  . COM  RULES &quot;
        RET        ; Near  return  to  DOS
ENTPT    ENDP
CSEG      ENDS
        END        ENTPT </pre>
<br />
 
[[[00774.htm|prev]]][[[00776.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .MODEL (Define Program Memory Segmentation Model) ===
 
The '''''.MODEL''directive establishes a predefined set of definitions, conventions, and modifications to various default operating behaviors of the assembler. These adjustments are designed to simply certain programming tasks and to allow a more seamless integration with routines written in high level languages.'''
 
'''Syntax'''
 
<br />
 
<pre>. MODEL  Memory - Model [ , Language - Type ] [ , OS - Type ] [ , Stack - Distance ] </pre>
'''''Memory-Model:'' <br />'''TINY''' <br />'''SMALL''' <br />'''COMPACT''' <br />'''MEDIUM''' <br />'''LARGE''' <br />'''HUGE''' <br />'''FLAT''' <br />'''
 
'''''Language-Type:'' <br />'''BASIC''' <br />'''C''' <br />'''FORTRAN''' <br />'''OPTLINK''' <br />'''PASCAL''' <br />'''STDCALL''' <br />'''SYSCALL''' <br />'''
 
'''''OS-Type:'' <br />'''OS_DOS''' <br />'''OS_OS2''' <br />'''
 
'''''Stack-Distance:'' <br />'''FARSTACK''' <br />'''NEARSTACK''' <br />'''
 
'''Remarks'''
 
The '''''.MODEL''directive should be placed at the top of the file, after any [[00745.htm|processor control]]directives, but before any of the following simplified segmentation directives are encountered:'''
 
�[[00765.htm|.CODE]] <br />�[[00766.htm|.CONST]] <br />�[[00767.htm|.DATA]] <br />�[[00768.htm|.DATA?]] <br />�[[00772.htm|.FARDATA]] <br />�[[00773.htm|.FARDATA?]] <br />�[[00779.htm|.STACK]]
 
Each of these directives close any segment that is currently opened, then open a different segment whose name and attributes are determined by the ''Memory-Model''argument.
 
 
 
'''Memory-Model'''
 
The fundamental purpose of establishing a programming memory model is to define how the program will be organized within the constraints of the segmented processor architecture. It defines whether there are single or multiple default code and data segments, or whether the default code and data segments are merged into a single segment. The operating system upon which the program will run is a determining factor of which memory models can be used. The following table describes these relationships. <br />
 
<pre>/------------------------------------------------------------\
|Memory  |Default |Default |Merged? |Operating Systems      |
|Model  |Code    |Data    |        |                        |
|--------+--------+--------+--------+------------------------|
|Tiny    |Near    |Near    |Yes    |DOS                    |
|--------+--------+--------+--------+------------------------|
|Small  |Near    |Near    |No      |DOS, 16-Bit OS/2, Win16 |
|--------+--------+--------+--------+------------------------|
|Medium  |Far    |Near    |No      |DOS, 16-Bit OS/2, Win16 |
|--------+--------+--------+--------+------------------------|
|Compact |Near    |Far    |No      |DOS, 16-Bit OS/2, Win16 |
|--------+--------+--------+--------+------------------------|
|Large  |Far    |Far    |No      |DOS, 16-Bit OS/2, Win16 |
|--------+--------+--------+--------+------------------------|
|Huge    |Far    |Far    |No      |DOS, 16-Bit OS/2, Win16 |
|--------+--------+--------+--------+------------------------|
|Flat    |Near    |Near    |Yes    |32-Bit OS/2, Win32      |
\------------------------------------------------------------/</pre>
The assembler creates the default code and data segments, then automatically generates an [[00788.htm|ASSUME]]CS:[[00178.htm|@code]]and an [[00788.htm|ASSUME]]DS:[[00181.htm|@data]]statement to refer to them.
 
 
 
'''Language-Type'''
 
Specifies the default naming convention for all public identifiers written that to the object file, and the method whereby parameters are passed to procedures (the '''''calling convention''). See the section on the [[00740.htm|PROC]]directive for a detailed explanation of the effects of the ''Language-Type''setting.'''
 
 
 
'''OS-Type'''
 
This parameter identifies the target operating system upon which the program will run, and is provided for compatibility with other assemblers. ALP ignores this parameter.
 
 
 
'''Stack-Distance'''
 
The '''NEARSTACK'''parameter causes the assembler to assume that the stack segment and the default data segment are the same, and that the DS register is equal to the SS register. This is the default setting. The assembler performs an automatic [[00788.htm|ASSUME]]SS:[[00181.htm|@data]]statement when a near stack is used.
 
The '''FARSTACK'''parameter causes the assembler to assume that the stack is in a different physical segment from that of the default data, and that SS register is not equal to DS. This is typically the case for code in a 16- bit dynamic link library that must use the caller's stack. The assembler performs an automatic [[00788.htm|ASSUME]]SS:STACK when this keyword is used. <br />
 
[[[00775.htm|prev]]][[[00777.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ORG (Adjust Segment Location Counter) ===
 
The '''ORG'''directive sets the location counter to the value of [[00255.htm|''Expression'']]. Subsequent instructions are generated beginning at this new location.
 
'''Syntax'''
 
<br />
 
<pre>ORG  Expression </pre>
'''Remarks'''
 
The assembler must know all names used in [[00255.htm|''Expression'']]on pass 1, and the value must be either absolute or in the same segment as the location counter.
 
The numeric value of [[00255.htm|''Expression'']]must not be a quantity larger than that which is representable by an unsigned integer having the same word size as the current segment.
 
You can use the current address operator ($) to refer to the current value of the location counter.
 
'''Example'''
 
<br />
 
<pre>ORG      120H
ORG      $ + 2      ; SKIP  NEXT  2  BYTES </pre>
To conditionally skip to the next 256-byte boundary: <br />
 
<pre>CSEG      SEGMENT      PAGE
BEGIN    =            $
        .
        .
        .
        IF  ( $ - BEGIN )  MOD  256
; IF  NOT  ALREADY  ON  256  BYTE  BOUNDARY
        ORG  ( $ - BEGIN ) + 256 - ( ( $ - BEGIN )  MOD  256 )
        ENDIF </pre>
<br />
 
[[[00776.htm|prev]]][[[00778.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== SEGMENT (Open a Program Information Segment) ===
 
Defines or reopens a segment called ''Segment-Name''which will contain all subsequently emitted code or data.
 
'''Syntax'''
 
<br />
 
<pre>Segment - Name  SEGMENT  [ align ] [ combine ] [ use ] [ ' class ' ] </pre>
'''Remarks'''
 
A segment definition may be followed by zero or more segment attributes, at most one from each of the following selections:
 
'''''align''Instructs the linker to align the segment at the next ''align''boundary. One of:'''
 
'''BYTE'''The next 8-bit boundary. <br />'''DWORD'''The next 32-bit boundary. <br />'''PAGE'''The next 256-byte boundary (4096 under 32-bit OS/2). <br />'''PARA'''The next 16-byte boundary (default). <br />'''WORD'''The next 16-bit boundary.
 
'''''combine''Controls how the linker will combine this segment with identically- named segments from other modules. One of:'''
 
'''AT'''''address''Locates the segment at the absolute paragraph given by ''address''. <br />'''COMMON'''Unioned with segments from other modules. <br />'''PRIVATE'''Will not be combined with other segments (default). <br />'''PUBLIC'''Concatenated to segments from other modules. <br />'''STACK'''Concatenated to segments from other modules. At load time: <br /> <br />SS=beginning of segment <br />SS:(E)SP=end of segment
 
'''''use''Word size of the segment.'''
 
'''USE16'''The segment will have a 16-bit word size. <br />'''USE32'''The segment will have a 32-bit word size.
 
'''class'''Instructs the linker to order segments according to the class name given by '''class'''. Segments will not be combined if their class names differ. <br />
 
[[[00777.htm|prev]]][[[00779.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .SEQ (Specifies Sequential Segment Ordering) ===
 
Orders segments sequentially (the default order).
 
'''Syntax'''
 
<br />
 
<pre>. SEQ </pre>
<br />
 
[[[00778.htm|prev]]][[[00780.htm|next]]][[[00763.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .STACK (Defines Default Stack Segment With Optional Size) ===
 
When used with '''.MODEL''', defines a stack segment with the segment name STACK. The optional ''Size''specifies the number of bytes for the stack (default 1024 ).
 
'''Syntax'''
 
<br />
 
<pre>. STACK  [ Size ] </pre>
'''Remarks'''
 
The '''.STACK'''directive does not leave the stack segment open when the statement is completed, since it is not a common practice to emit initialized data into the stack segment.
 
The name of the segment is STACK32 in flat model, and STACK for all other models. <br />
 
[[[00779.htm|prev]]][[[00781.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Type Definition ===
 
Type definition directives allow the creation of user-defined data types.
 
This section describes the following type definition directives:
 
RECORD <br />STRUCT/STRUC <br />TYPEDEF <br />UNION <br />
 
[[[00780.htm|prev]]][[[00782.htm|next]]][[[00780.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== RECORD (Define a Record Type Name) ===
 
A record is a bit pattern you define to format bytes, words, or dwords for bit-packing. The ''RecordName''becomes a [[00172.htm|''Record-TypeName'']]that can be used create record variables.
 
'''Syntax'''
 
<br />
 
<pre>RecordName  RECORD  FieldDeclaration  [ ,  [ LineBreak ]  FieldDeclaration  . . . ] </pre>
Where ''FieldDeclaration''has the following form: <br />
 
<pre>FieldName : Width [  =  InitialValue ] </pre>
The optional ''LineBreak''entry allows you to end a ''FieldDeclaration''with a comma, enter an optional [[00657.htm|''EndOfLine-Comment'']]followed by a physical ''NewLine'' character, then continue the record definition on the next line.
 
'''Remarks'''
 
The ''RecordName''and ''FieldName''entries are unique globally-scoped [[00149.htm|''Identifier'']]''s'' that must be specified. Upon successful processing of the '''RECORD''' definition, the ''RecordName''entry is converted to a [[00172.htm|''Record-TypeName'']], and all ''FieldNames''are converted to [[00159.htm|''Record-FieldName'']]''s''.
 
Each ''Width''entry in a ''FieldDeclaration''is specified as an [[00255.htm|''Expression'']]which must evaluate to an [[00599.htm|''Absolute-ExpressionType'']]. The cumulative value of all ''Width''entries becomes the total '''''RecordWidth''and must not exceed 32, the size of a DWORD, the maximum size for a [[00172.htm|''Record-TypeName'']]. The [[00587.htm|''Operand Size'']] of the record becomes 1 (BYTE) if the ''RecordWidth''is from 1 through 8, 2 ( WORD) if the ''RecordWidth''is from 9 through 16, and 4 (DWORD) if the ''RecordWidth''is from 17 through 32. Any other value causes an error. If the total number of bits in the ''RecordWidth''is not evenly divisible by the [[00587.htm|''Operand Size'']], the assembler right-justifies the fields into the least- significant bit positions of the record.'''
 
When a [[00159.htm|''Record-FieldName'']]is referenced in an expression, the value returned is the shift value required to access the field. The [[00563.htm|WIDTH]]operator is used on the [[00159.htm|''Record-FieldName'']]to return the width of the field in bits, and the [[00548.htm|MASK]]operator is used to obtain the value necessary for isolating the field within the record.
 
The ''InitialValue''entry contains the default value to used for the field when a record variable is allocated. If the field is at least 7 bits wide, you can initialize it to an ASCII character (for example, FIELD:7='Z').
 
To initialize a record, use the form: <br />
 
<pre>[ Identifier ]  Record - TypeName  Expression  [ ,  Expression  . . . ] </pre>
The [[00149.htm|''Identifier'']]entry is an optional name for the first byte, word, or dword of the reserved memory. The [[00172.htm|''Record-TypeName'']]defines the format and default field values, and is the ''RecordName''you assigned to the record in the '''RECORD'''directive.
 
At least one [[00255.htm|''Expression'']]entry must be specified; additional entries are optional. The [[00255.htm|''Expression'']]must resolve to a [[00609.htm|''Compound-ExpressionType'']], which may also be be duplicated by specifying it as a sub-expression of a [[00610.htm|''Duplicated-ExpressionType'']]. Each [[00609.htm|''Compound-ExpressionType'']]represents a single allocated record entry; each explicit sub-expression of the [[00609.htm|''Compound -ExpressionType'']]represents a field value which overrides the default ''InitialValue''for the field given in the record definition.
 
'''Example'''
 
Define the record fields; begin with the most significant fields first: <br />
 
<pre>MODULE  RECORD  R : 7 ,      ;  First  field .    &quot; ,  LineBreak &quot;  syntax
                E : 4 ,      ;  may  be  used  to  split  RECORD
                D : 5        ;  definition  across  multiple  lines </pre>
Fields are 7 bits, 4 bits, and 5 bits; the assembler gives no default value . Most significant byte first, this looks like: <br />
 
<pre>RRRR  RRRE  EEED  DDDD </pre>
To reserve its memory: <br />
 
<pre>STG _ FLD    MODULE      &lt; 7 , , 2 &gt;    ;  Initializer  is  a  Compound - ExpressionType </pre>
This defines R=7 and D=2 and leaves E unknown; it produces 2 bytes, the least significant byte first: <br />
 
<pre>02  0E </pre>
Define the record fields: <br />
 
<pre>AREA    RECORD    FLA : 8 = ' A ' , FLB : 8 = ' B ' </pre>
To reserve its memory: <br />
 
<pre>CHAR _ FLD    AREA  &lt; , ' P ' &gt; </pre>
This defines FLA='A' (the default) and changes FLB='P'.
 
To use a field in the record: <br />
 
<pre>DEFFIELD    RECORD    X : 3 , Y : 4 , Z : 9
            .
            .
            .
TABLE        DEFFIELD  10  DUP ( &lt; 0 , 2 , 255 &gt; )
            .
            .
            .
            MOV  DX , TABLE [ 2 ]
;  Move  data  from  record  to  register
;  other  than  segment  register
            AND  DX , MASK  Y
;  Mask  out  fields  X  and  Y
;  to  remove  unwanted  fields
;  The  MASK  of  Y  equals  1E00H
;  00011111000000000B  ( 1E00H )  Is  the  value
              MOV  CL , Y        ;  Get  shift  count
                              ;    9  is  the  value
              SHR  DX , CL        ;  Field  to  low - order
                              ;    bits  of  register ,  DX  is  now
                              ;    equal  to  the  value  of  field  Y
              MOV  CL , WIDTH  Y  ;  Get  number  of  bits
                              ;    in  field  -  4  is  the  value ,
                              ;    the  WIDTH  of  Y  is  4 </pre>
<br />
 
[[[00781.htm|prev]]][[[00783.htm|next]]][[[00780.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== STRUCT/STRUC (Define a Structure Type Name) ===
 
Defines a [[00173.htm|''Structure-TypeName'']]that represents an [[00711.htm|aggregate]]data type containing one or more fields.
 
'''Syntax'''
 
<br />
 
<pre>Structure - Name  STRUCT
  FieldDeclaration
    .
    .
    .
Structure - Name  ENDS </pre>
Where ''FieldDeclaration''has the following form: <br />
 
<pre>[ FieldName ]  Allocation - TypeName  InitialValue  [ ,  InitialValue  . . . ] </pre>
'''Remarks'''
 
The obsolete spelling for the '''STRUCT'''directive is '''STRUC'''.
 
The syntax for the ''FieldDeclaration''is that of a normal data allocation statement. See the section on [[00709.htm|Data Allocation]]for a full description of this syntax.
 
The various parts of the ''FieldDeclaration''are described as follows:
 
'''''FieldName''Each ''FieldName''entry is converted to [[00160.htm|''Structure-FieldName'']]when processing of the structure definition is complete. If this field is omitted and the '''''Allocation-TypeName''resolves to a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union-TypeName'']], then all of the fields defined within the imbedded structure or union are '''''promoted''to be visible at the same level as other ''FieldName''entries in the current structure given by the ''Structure-Name''.'''''''''
 
[[00709.htm|''Allocation-TypeName'']]The allowable values for this field are described in detail in the [[00709.htm|Data Allocation]]section. In modes other than [[00105.htm|M510]], the assembler accepts imbedded occurrences of other structures or unions by specifying an identifier that resolves to a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union- TypeName'']]in this field.
 
'''''InitialValue''The ''InitialValue''field must be an [[00255.htm|''Expression'']]that resolves to an [[00596.htm|''ExpressionType'']]appropriate for the [[00709.htm|''Allocation-TypeName'']]utilized in the ''FieldDeclaration''. The ''InitialValue''expressions become part of the structure type definition. These values are used as default initializers when an instance of the structure is allocated and no explict override values are specified for a particular field.'''
 
'''Example'''
 
Define a [[00173.htm|''Structure-TypeName'']]called '''Numbers''': <br />
 
<pre>  Numbers    STRUCT
    One        DB      0
    Two        WORD    0
                BYTE    3
    Four        DWORD    ?
  Numbers    ENDS </pre>
Allocate a structure variable called '''Values'''using the '''Numbers'''[[00173.htm|''Structure- TypeName'']], overriding the '''One, Two,'''and '''Four'''[[00160.htm|''Structure-FieldName'']]entries with explicit values, and the third (unnamed) entry is initialized with the default ''InitialValue''inherited from the ''FieldDeclaration'': <br />
 
<pre>  Values  Numbers  &lt; 1 ,  2 ,  ,  4 &gt; </pre>
<br />
 
[[[00782.htm|prev]]][[[00784.htm|next]]][[[00780.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== TYPEDEF (Create a User-Defined Type Name) ===
 
Defines a [[00174.htm|''Typedef-TypeName'']]that is an alias for another type declaration.
 
'''Syntax'''
 
<br />
 
<pre>TypeName  TYPEDEF  Type - Declaration </pre>
 
 
'''Remarks'''
 
The ''TypeName''entry is a unique globally-scoped [[00149.htm|''Identifier'']]that must be specified. Upon successful processing of the '''TYPEDEF'''directive, the ''TypeName''entry is converted to a [[00174.htm|''Typedef-TypeName'']]which can then be used in expressions or as a directive in data allocation statements.
 
The '''TYPEDEF'''directive can be used to create a direct alias for another intrinsic type (a [[00125.htm|''Scalar-TypeName'']], [[00172.htm|''Record-TypeName'']], [[00173.htm|''Structure-TypeName'']], [[00175.htm|''Union-TypeName'']], or other [[00174.htm|''Typedef-TypeName'']]), a pointer to another type, or it can be used to create vector types (arrays).
 
'''Examples'''
 
The following are examples of '''TYPEDEF'''usage: <br />
 
<pre>CHAR        typedef  byte                    ;  CHAR  is  an  alias  for  intrinsic  type
PCHAR      typedef  ptr  CHAR                ;  PCHAR  is  a  pointer  to  CHAR
 
BUFFER _ T    struct
  pLetter  PCHAR    ?                      ;  current  position  in  buffer
  Letters  CHAR      &quot; ABCDEF &quot; , 0              ;  array  of  characters
BUFFER _ T    ends
 
BUFFER      typedef  BUFFER _ T                ;  alias  for  intrinsic  type
PBUFFER    typedef  ptr  BUFFER _ T          ;  pointer  to  the  BUFFER  type
 
DATA        SEGMENT
HexChars    BUFFER    &lt; &gt;                      ;  allocate  structure  via  typedef
pHexChars  PBUFFER  offset  HexChars        ;  point  to  the  allocated  structure
DATA        ENDS </pre>
<br />
 
[[[00783.htm|prev]]][[[00785.htm|next]]][[[00780.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== UNION (Define a Union Type Name) ===
 
Defines a [[00175.htm|''Union-TypeName'']]that represents an [[00711.htm|aggregate]]data type containing one or more fields. All of the fields occupy the same physical position in storage.
 
'''Syntax'''
 
<br />
 
<pre>Union - Name  UNION
  FieldDeclaration
    .
    .
    .
Union - Name  ENDS </pre>
Where ''FieldDeclaration''has the following form: <br />
 
<pre>[ FieldName ]  Allocation - TypeName  InitialValue  [ ,  InitialValue  . . . ] </pre>
'''Remarks'''
 
This directive is not available in [[00105.htm|M510]]mode.
 
The syntax for the ''FieldDeclaration''is that of a normal data allocation statement. See the section on [[00709.htm|Data Allocation]]for a full description of this syntax.
 
The various parts of the ''FieldDeclaration''are described as follows:
 
'''''FieldName''Each ''FieldName''entry is converted to [[00161.htm|''Union-FieldName'']]when processing of the union definition is complete. If this field is omitted and the '''''Allocation-TypeName''resolves to a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union- TypeName'']], then all of the fields defined within the imbedded structure or union are '''''promoted''to be visible at the same level as other ''FieldName'' entries in the current union given by the ''Union-Name''.'''''''''
 
[[00709.htm|''Allocation-TypeName'']]The allowable values for this field are described in detail in the [[00709.htm|Data Allocation]]section. The assembler accepts imbedded occurrences of other structures or unions by specifying an identifier that resolves to a [[00173.htm|''Structure-TypeName'']]or [[00175.htm|''Union-TypeName'']]in this field.
 
'''''InitialValue''The ''InitialValue''field must be an [[00255.htm|''Expression'']]that resolves to an [[00596.htm|''ExpressionType'']]appropriate for the [[00709.htm|''Allocation-TypeName'']]utilized in the ''FieldDeclaration''. Only the ''InitialValue''expression for the first field becomes part of the union type definition; expressions specified for the remaining fields are ignored. This value is used as the default initializer when an instance of the union is allocated and no explict override value is specified for the field.'''
 
'''Example'''<br />
 
<pre>          . 386
IS _ sint32    equ  - 4
IS _ sint16    equ  - 2
IS _ sint8    equ  - 1
NO _ TYPE      equ    0
IS _ uint8    equ    1
IS _ uint16    equ    2
IS _ uint32    equ    4
 
TYPE _ T      typedef  SBYTE
 
DATA _ T      union
  uint8      BYTE    ?
  sint8      SBYTE    ?
  uint16    WORD    ?
  sint16    SWORD    ?
  uint32    DWORD    ?
  sint32    SDWORD  ?
DATA _ T      ends
 
VALUE _ T      struct
  DataType    TYPE _ T  NO _ TYPE
  DataValue  DATA _ T  { }
VALUE _ T      ends
 
            . data
Value        VALUE _ T  {  IS _ uint8 ,  {  1  }  }              ;  unsigned  8 - bit  value  of  1
 
          . code
 
;  Procedure :    IsNegative
;  Returns    :    1  in  EAX  if  Value . DataValue  holds  a  negative  number
;                0  in  EAX  if  Value . DataValue  holds  a  positive  number
 
IsNegative  proc
            cmp    Value . DataType ,  NO _ TYPE          ;  check  sign  of  TYPE _ T
            jns    short  Positive                    ;  if  positive ,  so  is  value
 
;  check  for  signed  8 - bit  integer
            cmp    Value . DataType ,  IS _ sint8
            jne    short  @ F                            ;  not  8 ,  check  for  16
            movsx  EAX ,  Value . DataValue . sint8        ;  convert  8  bits  to  32
            jmp    short  Check                        ;  and  check  the  value
 
;  check  for  signed  16 - bit  integer
@ @ :          cmp    Value . DataType ,  IS _ sint16
            jne    short  @ F                            ;  not  16 ,  check  for  32
            movsx  EAX ,  Value . DataValue . sint16      ;  convert  16  bits  to  32
            jmp    short  Check                        ;  and  check  the  value
 
;  check  for  signed  32 - bit  integer
@ @ :          cmp    Value . DataType ,  IS _ sint32
            jne    short  Positive                    ;  unknown ,  assume  positive
            mov    EAX ,  Value . DataValue . sint32      ;  get  full  32  bit  number
 
Check :      or      EAX , EAX                            ;  check  for  negative  value
            jns    short  Positive                    ;  no  sign  bit ,  positive
            mov    EAX ,  1                              ;  indicate  negative
            ret                                        ;  and  return
Positive :    mov    EAX ,  0                              ;  indicate  positive
            ret                                        ;  and  return
IsNegative  endp
end </pre>
<br />
 
[[[00784.htm|prev]]][[[00786.htm|next]]][[[00701.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Miscellaneous ===
 
This section describes the following miscellaneous directives:
 
= <br />.ABORT <br />ASSUME <br />EQU <br />LABEL <br />OPTION <br />.RADIX <br />
 
[[[00785.htm|prev]]][[[00787.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== = (Assign an Expression to an Assembler Variable) ===
 
The = directive lets you create a symbolic assembler-time variable. Numeric expressions may be assigned to the variable as many times as necessary.
 
'''Syntax'''
 
<br />
 
<pre>Name  =  Expression </pre>
'''Remarks'''
 
The '''='''directive is similar to the [[00791.htm|EQU]]assembler directive except you can redefine ''Name''without causing an error condition. However, the = directive is more restrictive about the allowable [[00596.htm|''ExpressionType'']]''s''that can be utilized in the [[00255.htm|''Expression'']]field, and it cannot be used to create [[00157.htm|''Text- EquateName'']]''s''.
 
''Name''is a globally-scoped [[00149.htm|''Identifier'']]. The [[00255.htm|''Expression'']]entry must evaluate to an [[00611.htm|''Operand-ExpressionType'']]. If an evaluation error occurs, or if the [[00255.htm|''Expression'']]references an external identifier, or if the [[00255.htm|''Expression'']] evaluates to one of the following [[00611.htm|''Operand-ExpressionType'']]''s'''':''
 
�[[00604.htm|''Indexed-ExpressionType'']] <br />�[[00605.htm|''Register-ExpressionType'']] <br />�[[00607.htm|''Floating-Point-ExpressionType'']] <br />�[[00609.htm|''Compound-ExpressionType'']] <br />�[[00610.htm|''Duplicated-ExpressionType'']]
 
then an error message is issued and the assignment does not take place. Otherwise, the [[00149.htm|''Identifier'']]is converted to a [[00156.htm|''Numeric-EquateName'']].
 
See also the [[00791.htm|EQU]]assembler directive and the [[00683.htm|EQU]]preprocessor directive.
 
'''Example'''
 
<br />
 
<pre>EMP  =  6        ; Establish  as  redefineable  numeric  equate
EMP  EQU  6      ; OK ,  value  is  the  same ,  EMP  remains  redefinable
EMP  EQU  7      ; Error ,  can ' t  change  value  with  EQU
EMP  =  7        ; OK ,  EMP  is  redefineable  with  =
EMP  =  EMP + 1    ; Can  refer  to  its  previous  definition </pre>
 
 
'''Note:'''The [[00585.htm|''Expression-Attribute'']]''s''inherited from the [[00255.htm|''Expression'']]during an assignment are not retained in subsequent assignments. For example: <br />
 
<pre>VECTOR  =  WORD  PTR  4            ;  Type - Declaration  attribute
        MOV  [ BX ] , VECTOR        ;  Store  the  4  as  a  word
VECTOR  =  6                      ;  Type - Declaration  attribute  discarded
        MOV  [ BX ] , VECTOR        ;  Error ,  no  size  for  operands </pre>
<br />
 
[[[00786.htm|prev]]][[[00788.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .ABORT (Terminate the Assembly) ===
 
Terminates the assembly at the point where the '''.ABORT'''directive is encountered. The remainder of the input stream is not read.
 
'''Syntax'''
 
<br />
 
<pre>. ABORT </pre>
'''Remarks'''
 
The '''.ABORT'''directive is only available in [[00105.htm|ALP]]mode <br />
 
[[[00787.htm|prev]]][[[00789.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ASSUME (Inform Assembler of Register Contents) ===
 
The '''ASSUME'''directive establishes an assembly-time association between a machine register and a program object or data type. By informing the assembler of the type of information to which a register points, certain programming tasks can be simplified and the assembler can perform some operations automatically.
 
'''Syntax'''
 
<br />
 
<pre>ASSUME  Association  [ ,  Association  . . . ] </pre>
'''''Association:'' <br />''Segment-Register-Assocation'' <br />''General-Purpose-Register-Assocation'' <br />'''NOTHING''' <br />'''
 
'''''Segment-Register-Association:'' <br />[[00122.htm|''Segment-Register'']]: [[00255.htm|''Expression'']] <br />[[00122.htm|''Segment-Register'']]: '''NOTHING''' <br />'''
 
'''''General-Purpose-Register-Association:'' <br />[[00122.htm|''General-Purpose-Register'']]: [[00250.htm|''Type-Declaration'']] <br />[[00122.htm|''General-Purpose-Register'']]: '''NOTHING''' <br />'''
 
'''Remarks'''
 
If the '''NOTHING'''keyword is specified for the ''Association''field, all register associations are cancelled.
 
If the '''NOTHING'''keyword is specified for a particular ''Segment-Register''or ''General-Purpose-Register'', only the association for that register is cancelled.
 
The following sections describe the two types of register associations:
 
�[[00789.htm|''Segment-Register-Association'']]
 
�[[00790.htm|''General-Purpose-Register-Association'']] <br />
 
[[[00788.htm|prev]]][[[00790.htm|next]]][[[00788.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Segment Register Association ===
 
A '''''Segment-Register-Association''establishes an assembly-time association between a [[00122.htm|''Segment-Register'']]and an expression that resolves to a [[00162.htm|''GroupName'']] or [[00170.htm|''SegmentName'']]. It allows the programmer to describe for the assembler what values are held in the segment registers at program run-time.'''
 
When the user program executes, all instructions that access memory do so through a particular segment register. To generate the correct encoding for an instruction that accesses a memory location, the assembler must know which segment register will be used in the effective memory address. In general, accessing a memory location from within a user program is done by referencing a named variable defined within a particular named segment.
 
Before accessing a named program variable (in a named memory segment), it is the programmer's responsibility to insure that the desired segment register actually references the correct physical segment at program run- time. Unless the '''ASSUME'''directive is used to describe this association, the assembler has no way of knowing ''which''segment register (if any) is addressing a named segment when a reference to a named variable contained therein is encountered. In this situation, the programmer is forced to use the [[00467.htm|Segment Override (: Operator)]]in every instruction to &quot;reach&quot; the desired variable and cause the assembler to generate the proper instruction encoding. The association established by the '''ASSUME'''directive allows the assembler to take over the task of verifying memory references and generating the appropriate instructions.
 
If you temporarily use a segment register to contain a value other than the segment or group identified in the '''ASSUME'''association, then you should reflect the change with a new '''ASSUME'''statement, or cancel the association with an '''ASSUME xS:NOTHING'''construct.
 
When the contents of a segment register are used for addressability, the register value should never contradict the association established for that register.
 
When the [[00775.htm|Reference]]directive is utilized and the program is designed to follow the conventions that it establishes, the '''ASSUME'''directive is no longer needed in most cases.
 
'''Example'''
 
<br />
 
<pre>Data    SEGMENT
Stuff  WORD  0
Data    ENDS
 
Code    SEGMENT
      ASSUME  NOTHING        ;  Cancel  all  register  assumptions
      mov  ax , Data            ;  Load  general - purpose  register  with  segment  frame ,
      mov  DS , ax              ;    then  establish  addressablity  through  DS
      mov  ES , ax              ;    and  ES .    The  assembler  doesn ' t  &quot; know &quot;  this  yet
      mov  Stuff ,  1          ;  Error ,  can ' t  reach  Stuff
      ASSUME  ES : Data        ;  Associate  ES  register  with  Data  segment
      add  Stuff ,  bx          ;  Now  we  can  reach  Stuff ,  but  the  assembler  needs
                              ;    to  generate  an  ES  override  instruction  byte
      ASSUME  DS : SEG  Stuff    ;  Expression  to  extract  the  segment  value  of  Stuff
                              ;    This  has  the  same  effect  as  ASSUME  DS : Data
                              ;    Now  both  DS  and  ES  are  associated  with  Data
      add  Stuff ,  cx          ;  This  time ,  the  instruction  doesn ' t  need  an
                              ;    override  byte  because  DS  is  the  default
                              ;    register  for  normal  accesses  to  memory
      ASSUME  DS : NOTHING      ;  Cancel  the  association  between  DS  and  Data
      add  Stuff ,  dx          ;  Once  again ,  the  ES  override  is  generated
      add  DS : Stuff ,  dx      ;  Must  use  &quot; force &quot;  if  we  want  the  default  encoding
Code    ends
      end </pre>
'''Warning''':
 
If an '''ASSUME CS''':[[00255.htm|''Expression'']]is placed before the code segment it is referencing, the assembler will ignore the '''ASSUME'''. The '''ASSUME CS''':[[00255.htm|''Expression'']]statement must follow the '''SEGMENT'''definition statement of the code segment it is referencing.
 
The '''ASSUME'''statement for the '''CS'''register should be placed immediately following the code [[00777.htm|SEGMENT]]statement, before any labels are defined in that code segment. <br />
 
[[[00789.htm|prev]]][[[00791.htm|next]]][[[00788.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== General-Purpose Register Association ===
 
A '''''General-Purpose-Register-Association''establishes an assembly-time association between a [[00122.htm|''General-Purpose-Register'']]and a [[00250.htm|''Type-Declaration'']]. It allows the programmer to describe for the assembler what type of data is being held in the general purpose register at program run-time.'''
 
This feature can be very useful when the programmer is treating a general- purpose register as a &quot;pointer&quot; to a particular type of storage. If this &quot; pointer&quot; is being utilized many times in the program, (perhaps changing in value but never in the type of data to which it points), the '''ASSUME''' directive can be used to associate the register with the type of data to which it points. This frees the programmer from having to use an explicit [[00461.htm|Type Conversion (PTR Operator)]]every time the register is used to access memory.
 
A register may only be associated with a data type whose operand size matches that of the register. For instance, the following construct is illegal: <br />
 
<pre>    ASSUME  EBX : BYTE            ;  Error ,  EBX  is  a  DWORD  register </pre>
The most useful situation is for the register to contain a pointer to another data type. In this situation, the [[00573.htm|Indirection ([] Operator)]]may be used store or retrieve data through the register without the need for an explicit conversion operation: <br />
 
<pre>    ASSUME  EDI : NOTHING                ;  This  is  the  assembler  default  setting
    MOV      [ EDI ] ,  1                  ;  What  is  the  size  supposed  to  be ?
    MOV      byte  ptr  [ EDI ] ,  1        ;  Fixes  the  problem ,  but  this  can  get  tiring
    ASSUME  EDI : PTR  BYTE              ;  EDI  is  now  a  pointer  to  a  byte
    MOV      [ EDI ] ,  1                  ;  assembler  knows  what  to  do  with  this  now
    INC      [ EDI ]                      ;  and  this  too </pre>
The following constructs are legal but not particularly useful since they simply restate what is already known about the registers (the operand size) , and the assembler doesn't enforce a strict level of type checking against register operands: <br />
 
<pre>    ASSUME  ECX : SDWORD                ;  Signed  double - word  matches  size  of  ECX
    ASSUME  EBX : DWORD                  ;  Unsigned  double - word  matches  size  of  EBX
    MOV      ECX ,  0FFFFEEEEh          ;  Register  type - checking  is  not  strict
    MOV      EBX ,  - 1                    ;    enough  to  flag  these  as  errors </pre>
In fact, any data type that matches the size of the register may be used; the assembler checks the sizes and reports mismatches, but effectively ignores any settings that are not pointers to other types. Consider the following example: <br />
 
<pre>    STRUCT _ T  STRUCT
      One      BYTE  1
      Two      BYTE  2
      Three    BYTE  3
      Four    BYTE  4
    STRUCT _ T  ENDS
 
    ASSUME  EBX : STRUCT _ T              ;  Ok ,  STRUCT _ T  is  4  bytes  in  size
    MOV      EBX ,  - 1                    ;  Legal ,  but  not  very  meaningful . . .
 
    ;  A  more  useful  situation  ( given  that  EBX  is  now  holding  data  of  type
    ;  STRUCT _ T )  would  be  for  the  assembler  to  allow  the  following  notation :
 
    MOV      EBX ,  {  4 ,  3 ,  2 ,  1  }      ;  Hypothetical  ( UNSUPPORTED ! )  syntax . . .
 
    ;  It  would  also  be  nice  at  this  point  if  the  symbolic  debugger  could
    ;  show  us  the  value  of  EBX  in  the  appropriate  format ,  but  the  assembler
    ;  does  not  support  the  emitting  of  context - sensitive  symbolic  debugging
    ;  information . </pre>
[[[00790.htm|prev]]][[[00792.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== EQU (Assign an Expression to a Symbolic Constant) ===
 
The '''EQU'''directive assigns the value of [[00255.htm|''Expression'']]to ''Name''.
 
'''Syntax'''
 
<br />
 
<pre>Name  EQU  Expression </pre>
'''Remarks'''
 
If ''Name''has already been defined as a [[00156.htm|''Numeric-EquateName'']]and its currently assigned value differs from the value given by [[00255.htm|''Expression'']], an error message is produced. Unlike symbols created with the = (equal sign) directive, symbols created with the '''EQU'''directive cannot be redefined with different values.
 
The [[00255.htm|''Expression'']]entry must evaluate to an [[00611.htm|''Operand-ExpressionType'']]. If an evaluation error occurs or if the [[00255.htm|''Expression'']]evaluates to one of the following [[00611.htm|''Operand-ExpressionType'']]''s'''':''
 
�[[00604.htm|''Indexed-ExpressionType'']] <br />�[[00607.htm|''Floating-Point-ExpressionType'']] <br />�[[00609.htm|''Compound-ExpressionType'']] <br />�[[00610.htm|''Duplicated-ExpressionType'']]
 
then the [[00149.htm|''Identifier'']]is converted to a [[00157.htm|''Text-EquateName'']]. Otherwise, the [[00149.htm|''Identifier'']]is converted to a [[00156.htm|''Numeric-EquateName'']].
 
See also [[00683.htm|EQU]]and [[00786.htm|=]].
 
'''Example'''
 
<br />
 
<pre>A      EQU    &lt; BP  + &gt;    ; explicit  text  literal ,  A  is  a  text  equate
B      EQU    BP  +      ; invalid  expression  -  text  equate  equivalent  to  A
B      EQU    1  +  2    ; valid  expression  -  but  still  a  text  equate  &lt; 1  +  2 &gt;
C      EQU    1  +  2    ; converted  to  assembler  symbolic  constant ,  value  =  3
C      EQU    &lt; 3 &gt;      ; illegal ,  cannot  convert  back  to  text  equate </pre>
<br />
 
[[[00791.htm|prev]]][[[00793.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== LABEL (Associate a Symbolic Name With Current Address) ===
 
The '''LABEL'''directive defines the following attributes of ''Name:''
 
�Segment: current segment being assembled <br />�Offset: current position within this segment <br />�Type: the operand of the '''LABEL'''directive <br />
 
'''Syntax'''
 
<br />
 
<pre>Name  LABEL  Type - Declaration
  or
Name :
  or
Name : : </pre>
'''Remarks'''
 
The '''LABEL'''directive provides a method of labeling a memory location and assigning it a type without allocating any storage. It can be used to create multiple labels of differing types that are aliases for the same memory location.
 
The ''Name''entry is an [[00149.htm|''Identifier'']]that is converted to a [[00163.htm|''LabelName'']]according to the value given by [[00250.htm|''Type-Declaration'']]. See the section on [[00163.htm|label names]]for more information on the details of this conversion.
 
The ''':'''and '''::'''forms of this directive are used for defining code labels. In this case, the ''Name''entry is converted to a [[00165.htm|''Target-LabelName'']]. The double- colon form of the directive is used when the ''Name''must be visible outside of the procedure block in which it is defined.
 
'''Example'''
 
To refer to a data area but use a length different from the original definition of that area: <br />
 
<pre>BARRAY    LABEL      BYTE
ARRAY    DW        100  DUP ( 0 )
            .
            .
            .
        ADD        AL , BARRAY [ 99 ]    ; ADD  100th  BYTE    TO  AL
        ADD        AX , ARRAY [ 98 ]      ; ADD  50th  WORD    TO  AX </pre>
To define multiple entry points within a procedure: <br />
 
<pre>SUBRT    PROC      FAR
        .
        .
        .
SUB2      LABEL    FAR    ; Should  have  same  attribute  as  containing  PROC
        .
        .
        .
        RET
SUBRT    ENDP </pre>
<br />
 
[[[00792.htm|prev]]][[[00794.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== OPTION (Modify Default Behaviors) ===
 
The '''OPTION'''directive allows the user to alter certain default behaviors of the assembler, normally to provide backward compatibility with older assemblers. The '''OPTION'''directive is not available when assembling in [[00105.htm|M510]] mode.
 
'''Syntax'''
 
<br />
 
<pre>OPTION  Option - Item  [ ,  [ LineBreak ]  Option - Item  . . . ] </pre>
'''Remarks'''
 
The '''''Option-Item''arguments are defined as follows (the underlined keywords denote the default values):'''
 
'''DOTNAME'''| ''NODOTNAME''Allows user identifiers to begin with an introductory dot (.) character.
 
'''EXPR16'''| ''EXPR32''Specifies whether expressions are evaluated using 16-bit or 32-bit arithmetic. Some programs may require reverting back to '''EXPR16'''in order to assemble without problems. Once this value has been set it cannot be changed. The use of a processor selection directive to select a 32-bit processor is equivalent to selecting '''OPTION EXPR32''', which prevents any further attempt to select '''OPTION EXPR16'''.
 
'''LANGUAGE''':[[00131.htm|''Language-Name'']]Specifies the default language type for identifiers with '''PUBLIC'''or '''EXPORT'''visibility. This option overrides any setting given in the [[00775.htm|.MODEL]]directive.
 
'''OFFSET''':''Offset-Type''Determines how relocatable offset values are written to the object file output, encoded in the form of a linker &quot;fixup&quot; record. The possible values for ''Offset-Type''are '''SEGMENT''', ''GROUP'', and '''FLAT'''.
 
'''OLDSTRUCTS'''| ''NOOLDSTRUCTS''The '''OLDSTRUCTS'''keyword causes structure field names to become global identifiers rather than local names private to the structure type. It also prevents the [[00482.htm|Structure/Union Field Selection (. Operator)]]from performing strict checking on its operands, requiring its left operand to have a structure type and its right operand to be the name of a field contained therein.
 
'''PROC''':''Visibility''Specifies the default visibility for procedure names. This can be one of '''PRIVATE''', ''PUBLIC'', or '''EXPORT'''.
 
'''SCOPED'''| '''NOSCOPED'''The '''NOSCOPED'''keyword forces all code label names defined within procedures to be visible to the entire module and not just from within the defining procedure.
 
'''SEGMENT''':''Address-Size''Explicitly sets the default address size value. This is used to control the address size of segments that are opened without explict '''USE16'''or '''USE32'''keywords, and of global identifiers that are declared outside of segment boundaries. The possible values for ''Address- Size''are '''USE16''', '''USE32''', and '''FLAT'''. <br />
 
[[[00793.htm|prev]]][[[00795.htm|next]]][[[00785.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== .RADIX (Set the Default Base for Numeric Literals) ===
 
The '''.RADIX'''directive lets you change the default '''RADIX'''(decimal) to base 2, 8, 10, or 16.
 
'''Syntax'''
 
<br />
 
<pre>. RADIX  Expression </pre>
'''Remarks'''
 
The [[00255.htm|''Expression'']]entry is in decimal radix regardless of the current radix setting.
 
The '''.RADIX'''directive does not affect real numbers initialized as variables with '''DD''', '''DQ''', or '''DT'''.
 
When using '''.RADIX 16''', be aware that if the hex constant ends in either B or D, the assembler thinks that the B or D is a request to cancel the current radix specification with a base of binary or decimal, respectively. In such cases, add the H base override (just as if '''.RADIX 16'''were not in use).
 
'''Example'''
 
The statement: <br />
 
<pre>. RADIX    16
DW    120B </pre>
produces an error because 2 is not a valid binary number. The correct specification is: <br />
 
<pre>DW    120BH </pre>
The following example: <br />
 
<pre>. RADIX    16
DW    89CD </pre>
also produces an error because C is not a valid decimal number. The correct specification is: <br />
 
<pre>DW    89CDH </pre>
The dangerous case is when no error is produced. For example: <br />
 
<pre>. RADIX    16
DW  120D </pre>
produces a constant whose value is 120 decimal, not '120D' hex, which might have been the intended value.
 
The following two move instructions are the same: <br />
 
<pre>MOV    BX , OFFH
. RADIX    16
MOV    BX , OFF </pre>
The following example: <br />
 
<pre>. RADIX  8
DQ  19 . 0      ;  Treated  as  decimal </pre>
produces a constant whose value is 19 decimal because 19.0 is a real number . However, if you leave off the decimal point, the following: <br />
 
<pre>. RADIX    8
DQ    19  ;  uses  current  radix </pre>
produces a syntax error because nine is not a valid number in .RADIX 8. <br />
 
[[[00794.htm|prev]]][[[00796.htm|next]]][[[toc.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Processor Reference ===
 
This chapter presents an overview of the instruction set and lists the complete instruction set in alphabetical order. For each instruction, the forms are given for each operand combination, including object code produced, operands required, execution time, and a description. For each instruction, there is an operational description and a summary of exceptions generated.
 
[[[00795.htm|prev]]][[[00797.htm|next]]][[[00795.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Intel Instruction Set Overview ===
 
This section contains an introduction to the Intel instruction set and presents the terminology necessary to understand the encoding and operation of each individual instruction.
 
[[[00796.htm|prev]]][[[00798.htm|next]]][[[00796.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operand-Size and Address-Size Attributes ===
 
When executing an instruction, the processor can address memory using either 16 or 32-bit addresses. Consequently, each instruction that uses memory addresses has associated with it an address-size attribute of either 16 or 32 bits. The use of 16-bit addresses implies both the use of 16-bit displacements in instructions and the generation of 16-bit address offsets (segment relative addresses) as the result of the effective address calculations. 32-bit addresses imply the use of 32-bit displacements and the generation of 32-bit address offsets. Similarly, an instruction that accesses words (16 bits) or doublewords (32 bits) has an operand-size attribute of either 16 or 32 bits.
 
The attributes are determined by a combination of defaults, instruction prefixes, and (for programs executing in protected mode) size-specification bits in segment descriptors.
 
[[[00797.htm|prev]]][[[00799.htm|next]]][[[00797.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Default Segment Attribute ===
 
For programs running in protected mode, the D bit in executable-segment descriptors specifies the default attribute for both address size and operand size. These default attributes apply to the execution of all instructions in the segment. A clear D bit sets the default address size and operand size to 16 bits; a set D bit, to 32 bits.
 
Programs that execute in real mode or virtual-8086 mode have 16-bit addresses and operands by default.
 
[[[00798.htm|prev]]][[[00800.htm|next]]][[[00797.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operand-Size and Address-Size Instruction Prefixes ===
 
The internal encoding of an instruction can include two byte-long prefixes: the address-size prefix, 67H, and the operand-size prefix, 66H. (A later section, &quot;Instruction Format,&quot; shows the position of the prefixes in an instruction's encoding.) These prefixes ''override''the default segment attributes for the instruction that follows. The following table shows the effect of each possible combination of defaults and overrides.
 
'''Effective Size Attributes'''<br />
 
<pre>/--------------------------------------------------------------------\
|Segment Default D = ...    |0  |0  |0  |0  |1  |1  |1  |1  |
|----------------------------+----+----+----+----+----+----+----+----|
|Operand-Size Prefix 66H    |N  |N  |Y  |Y  |N  |N  |Y  |Y  |
|----------------------------+----+----+----+----+----+----+----+----|
|Address-Size Prefix 67H    |N  |Y  |N  |Y  |N  |Y  |N  |Y  |
|----------------------------+----+----+----+----+----+----+----+----|
|Effective Operand Size      |16  |16  |32  |32  |32  |32  |16  |16  |
|----------------------------+----+----+----+----+----+----+----+----|
|Effective Address Size      |16  |32  |16  |32  |32  |16  |32  |16  |
\--------------------------------------------------------------------/</pre>
Y = Yes, this instruction prefix is present <br />N = No, this instruction prefix is not present
 
[[[00799.htm|prev]]][[[00801.htm|next]]][[[00797.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Address-Size Attribute for Stack ===
 
Instructions that use the stack implicitly (for example: POP EAX) also have a stack address-size attribute of either 16 or 32 bits. Instructions with a stack address-size attribute of 16 use the 16-bit SP stack pointer register; instructions with a stack address-size attribute of 32 bits use the 32-bit ESP register to form the address of the top of the stack.
 
The stack address-size attribute is controlled by the B bit of the data- segment descriptor in the SS register. A value of zero in the B bit selects a stack address-size attribute of 16; a value of one selects a stack address-size attribute of 32.
 
[[[00800.htm|prev]]][[[00802.htm|next]]][[[00796.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Format ===
 
All instruction encodings are subsets of the general instruction format shown in the following figure. Instructions consist of optional instruction prefixes (in any order), one or two primary opcode bytes, possibly an address specifier consisting of the ModR/M byte and the SIB (Scale Index Base) byte, a displacement, if required, and an immediate data field, if required. <br />
 
<pre>Instruction Format
 
/-------------------------------------------------------------\
|  /----------------------------------------------------\    |
|  | INSTRUCTION  |  ADDRESS-  | OPERAND-  | SEGMENT  |    |
|  |    PREFIX    | SIZE PREFIX |SIZE PREFIX | OVERRIDE |    |
|  |----------------------------------------------------|    |
|  |    0 OR 1        0 OR 1      0 OR 1      0 OR 1  |    |
|  |----------------------------------------------------|    |
|  |                                                    |    |
|  |                  NUMBER OF BYTES                  |    |
|  \----------------------------------------------------/    |
|                                                            |
|  /----------------------------------------------------\    |
|  |  OPCODE | MODR/M | SIB | DISPLACEMENT | IMMEDIATE  |    |
|  |----------------------------------------------------|    |
|  |  1 OR 2  0 OR 1  0 OR 1  0,1,2 OR 4    0,1,2 OR 4|    |
|  |----------------------------------------------------|    |
|  |                  NUMBER OF BYTES                  |    |
|  \----------------------------------------------------/    |
\-------------------------------------------------------------/</pre>
Smaller encoding fields can be defined within the primary opcode or opcodes . These fields define the direction of the operation, the size of the displacements, the register encoding, or sign extension; encoding fields vary depending on the class of operation.
 
Most instructions that can refer to an operand in memory have an addressing form byte following the primary opcode byte(s). This byte, called the ModR/ M byte, specifies the address form to be used. Certain encodings of the ModR/M byte indicate a second addressing byte, the SIB (Scale Index Base) byte, which follows the ModR/M byte and is required to fully specify the addressing form.
 
Addressing forms can include a displacement immediately following either the ModR/M or SIB byte. If a displacement is present, it can be 8-, 16- or 32-bits.
 
If the instruction specifies an immediate operand, the immediate operand always follows any displacement bytes. The immediate operand, if specified, is always the last field of the instruction.
 
Zero or one bytes are reserved for each group of prefixes. The prefixes are grouped as follows:
 
1.Instruction Prefixes: REP, REPE/REPZ, REPNE/REPNZ, LOCK
 
2.Segment Override Prefixes: CS, SS, DS, ES, FS, GS
 
3.Operand Size Override
 
4.Address Size Override <br />
 
For each instruction, one prefix may be used from each group. The effect of redundant prefixes (more than one prefix from a group) is undefined and may vary from processor to processor. The prefixes may come in any order.
 
The following are the allowable instruction prefix codes: <br />
 
<pre>F3H    REP prefix (used only with string instructions)
F3H    REPE/REPZ prefix (used only with string instructions)
F2H    REPNE/REPNZ prefix (used only with string instructions)
F0H    LOCK prefix </pre>
The following are the segment override prefixes: <br />
 
<pre>2EH    CS segment override prefix
36H    SS segment override prefix
3EH    DS segment override prefix
26H    ES segment override prefix
64H    FS segment override prefix
65H    GS segment override prefix
66H    Operand-size override
67H    Address-size override </pre>
[[[00801.htm|prev]]][[[00803.htm|next]]][[[00801.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ModR/M and SIB Bytes ===
 
The ModR/M and SIB bytes follow the opcode byte(s) in many of the processor instructions. They contain the following information:
 
�The indexing type or register number to be used in the instruction
 
�The register to be used, or more information to select the instruction
 
�The base, index, and scale information <br />
 
The ModR/M byte contains three fields of information:
 
�The '''mod'''field, which occupies the two most significant bits of the byte, combines with the r/m field to form 32 possible values: eight registers and 24 indexing modes.
 
�The '''reg'''field, which occupies the next three bits following the mod field, specifies either a register number or three more bits of opcode information . The meaning of the reg field is determined by the first (opcode) byte of the instruction.
 
�The '''r/m'''field, which occupies the three least significant bits of the byte , can specify a register as the location of an operand, or can form part of the addressing-mode encoding in combination with the '''mod'''field as described above. <br />
 
The based indexed forms of 32-bit addressing require the SIB byte. The presence of the SIB byte is indicated by certain encodings of the ModR/M byte. The SIB byte then includes the following fields:
 
�The '''ss'''field, which occupies the two most significant bits of the byte, specifies the scale factor.
 
�The '''index'''field, which occupies the next three bits following the '''ss'''field and specifies the register number of the index register.
 
�The '''base'''field, which occupies the three least significant bits of the byte, specifies the register number of the base register. <br /><br />
 
<pre>ModR/M and SIB Byte Formats
 
/------------------------------------------------\
|                  MODR/M BYTE                  |
|                                                |
|    7    6    5    4    3  2    1    0    |
|  /------------------------------------------\ |
|  |  MOD    |  REG/OPCODE  |    R/M      | |
|  \------------------------------------------/ |
|                                                |
|            SIB (SCALE INDEX BASE) BYTE        |
|                                                |
|    7    6    5    4    3  2    1    0    |
|  /------------------------------------------\ |
|  |    SS    |    INDEX      |    BASE    | |
|  \------------------------------------------/ |
|                                                |
\------------------------------------------------/</pre>
[[[00802.htm|prev]]][[[00804.htm|next]]][[[00802.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== 16-Bit Addressing Forms with the ModR/M Byte ===
 
<br />
 
<pre>/-------------------------------------------------------------------------------\
| r8(/r)                        | AL  | CL  | DL  | BL  | AH  | CH  | DH  | BH  |
| r16(/r)                      | AX  | CX  | DX  | BX  | SP  | BP  | SI  | DI  |
| r32(/r)                      | EAX | ECX | EDX | EBX | ESP | EBP | ESI | EDI |
| /digit (Opcode)              | 0  | 1  | 2  | 3  | 4  | 5  | 6  | 7  |
| REG =                        | 000 | 001 | 010 | 011 | 100 | 101 | 110 | 111 |
|-------------------------------+-----------------------------------------------|
| Effective      | MOD |  R/M  |        MODR/M Values in Hexadecimal          |
| Address        |    |      |                                              |
|-----------------+-----+-------+-----------------------------------------------|
| [BX+SI]        | 00  |  000  | 00  | 08  | 10  | 18  | 20  | 28  | 30  | 38  |
| [BX+DI]        |    |  001  | 01  | 09  | 11  | 19  | 21  | 29  | 31  | 39  |
| [BP+SI]        |    |  010  | 02  | 0A  | 12  | 1A  | 22  | 2A  | 32  | 3A  |
| [BP+DI]        |    |  011  | 03  | 0B  | 13  | 1B  | 23  | 2B  | 33  | 3B  |
| [SI]            |    |  100  | 04  | 0C  | 14  | 1C  | 24  | 2C  | 34  | 3C  |
| [DI]            |    |  101  | 05  | 0D  | 15  | 1D  | 25  | 2D  | 35  | 3D  |
| disp16          |    |  110  | 06  | 0E  | 16  | 1E  | 26  | 2E  | 36  | 3E  |
| [BX]            |    |  111  | 07  | 0F  | 17  | 1F  | 27  | 2F  | 37  | 3F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| [BX+SI]+disp8  | 01  |  000  | 40  | 48  | 50  | 58  | 60  | 68  | 70  | 78  |
| [BX+DI]+disp8  |    |  001  | 41  | 49  | 51  | 59  | 61  | 69  | 71  | 79  |
| [BP+SI]+disp8  |    |  010  | 42  | 4A  | 52  | 5A  | 62  | 6A  | 72  | 7A  |
| [BP+DI]+disp8  |    |  011  | 43  | 4B  | 53  | 5B  | 63  | 6B  | 73  | 7B  |
| [SI]+disp8      |    |  100  | 44  | 4C  | 54  | 5C  | 64  | 6C  | 74  | 7C  |
| [DI]+disp8      |    |  101  | 45  | 4D  | 55  | 5D  | 65  | 6D  | 75  | 7D  |
| [BP]+disp8      |    |  110  | 46  | 4E  | 56  | 5E  | 66  | 6E  | 76  | 7E  |
| [BX]+disp8      |    |  111  | 47  | 4F  | 57  | 5F  | 67  | 6F  | 77  | 7F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| [BX+SI]+disp16  | 10  |  000  | 80  | 88  | 90  | 98  | A0  | A8  | B0  | B8  |
| [BX+DI]+disp16  |    |  001  | 81  | 89  | 91  | 99  | A1  | A9  | B1  | B9  |
| [BP+SI]+disp16  |    |  010  | 82  | 8A  | 92  | 9A  | A2  | AA  | B2  | BA  |
| [BP+DI]+disp16  |    |  011  | 83  | 8B  | 93  | 9B  | A3  | AB  | B3  | BB  |
| [SI]+disp16    |    |  100  | 84  | 8C  | 94  | 9C  | A4  | AC  | B4  | BC  |
| [DI]+disp16    |    |  101  | 85  | 8D  | 95  | 9D  | A5  | AD  | B5  | BD  |
| [BP]+disp16    |    |  110  | 86  | 8E  | 96  | 9E  | A6  | AE  | B6  | BE  |
| [BX]+disp16    |    |  111  | 87  | 8F  | 97  | 9F  | A7  | AF  | B7  | BF  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| EAX/AX/AL      | 11  |  000  | C0  | C8  | D0  | D8  | E0  | E8  | F0  | F8  |
| ECX/CX/CL      |    |  001  | C1  | C9  | D1  | D9  | E1  | E9  | F1  | F9  |
| EDX/DX/DL      |    |  010  | C2  | CA  | D2  | DA  | E2  | EA  | F2  | FA  |
| EBX/BX/BL      |    |  011  | C3  | CB  | D3  | DB  | E3  | EB  | F3  | FB  |
| ESP/SP/AH      |    |  100  | C4  | CC  | D4  | DC  | E4  | EC  | F4  | FC  |
| EBP/BP/CH      |    |  101  | C5  | CD  | D5  | DD  | E5  | ED  | F5  | FD  |
| ESI/SI/DH      |    |  110  | C6  | CE  | D6  | DE  | E6  | EE  | F6  | FE  |
| EDI/DI/BH      |    |  111  | C7  | CF  | D7  | DF  | E7  | EF  | F7  | FF  |
\-------------------------------------------------------------------------------/</pre>
'''Notes:'''
 
1.'''disp8'''denotes an 8-bit displacement following the ModR/M byte, to be sign-extended and added to the index.
 
2.'''disp16'''denotes a 16-bit displacement following the ModR/M byte, to be added to the index. Default segment register is SS for the effective addresses containing a BP index, DS for other effective addresses. <br />
 
[[[00803.htm|prev]]][[[00805.htm|next]]][[[00802.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== 32-Bit Addressing Forms with the ModR/M Byte ===
 
<br />
 
<pre>/-------------------------------------------------------------------------------\
| r8(/r)                        | AL  | CL  | DL  | BL  | AH  | CH  | DH  | BH  |
| r16(/r)                      | AX  | CX  | DX  | BX  | SP  | BP  | SI  | DI  |
| r32(/r)                      | EAX | ECX | EDX | EBX | ESP | EBP | ESI | EDI |
| /digit (Opcode)              | 0  | 1  | 2  | 3  | 4  | 5  | 6  | 7  |
| REG =                        | 000 | 001 | 010 | 011 | 100 | 101 | 110 | 111 |
|-------------------------------+-----------------------------------------------|
| Effective      | MOD |  R/M  |        MODR/M Values in Hexadecimal          |
| Address        |    |      |                                              |
|-----------------+-----+-------+-----------------------------------------------|
| [EAX]          | 00  |  000  | 00  | 08  | 10  | 18  | 20  | 28  | 30  | 38  |
| [ECX]          |    |  001  | 01  | 09  | 11  | 19  | 21  | 29  | 31  | 39  |
| [EDX]          |    |  010  | 02  | 0A  | 12  | 1A  | 22  | 2A  | 32  | 3A  |
| [EBX]          |    |  011  | 03  | 0B  | 13  | 1B  | 23  | 2B  | 33  | 3B  |
| [--][--]        |    |  100  | 04  | 0C  | 14  | 1C  | 24  | 2C  | 34  | 3C  |
| disp32          |    |  101  | 05  | 0D  | 15  | 1D  | 25  | 2D  | 35  | 3D  |
| [ESI]          |    |  110  | 06  | 0E  | 16  | 1E  | 26  | 2E  | 36  | 3E  |
| [EDI]          |    |  111  | 07  | 0F  | 17  | 1F  | 27  | 2F  | 37  | 3F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| disp8[EAX]      | 01  |  000  | 40  | 48  | 50  | 58  | 60  | 68  | 70  | 78  |
| disp8[ECX]      |    |  001  | 41  | 49  | 51  | 59  | 61  | 69  | 71  | 79  |
| disp8[EDX]      |    |  010  | 42  | 4A  | 52  | 5A  | 62  | 6A  | 72  | 7A  |
| disp8[EBX]      |    |  011  | 43  | 4B  | 53  | 5B  | 63  | 6B  | 73  | 7B  |
| disp8[--][--]  |    |  100  | 44  | 4C  | 54  | 5C  | 64  | 6C  | 74  | 7C  |
| disp8[EBP]      |    |  101  | 45  | 4D  | 55  | 5D  | 65  | 6D  | 75  | 7D  |
| disp8[ESI]      |    |  110  | 46  | 4E  | 56  | 5E  | 66  | 6E  | 76  | 7E  |
| disp8[EDI]      |    |  111  | 47  | 4F  | 57  | 5F  | 67  | 6F  | 77  | 7F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| disp32[EAX]    | 10  |  000  | 80  | 88  | 90  | 98  | A0  | A8  | B0  | B8  |
| disp32[ECX]    |    |  001  | 81  | 89  | 91  | 99  | A1  | A9  | B1  | B9  |
| disp32[EDX]    |    |  010  | 82  | 8A  | 92  | 9A  | A2  | AA  | B2  | BA  |
| disp32[EBX]    |    |  011  | 83  | 8B  | 93  | 9B  | A3  | AB  | B3  | BB  |
| disp32[--][--]  |    |  100  | 84  | 8C  | 94  | 9C  | A4  | AC  | B4  | BC  |
| disp32[EBP]    |    |  101  | 85  | 8D  | 95  | 9D  | A5  | AD  | B5  | BD  |
| disp32[ESI]    |    |  110  | 86  | 8E  | 96  | 9E  | A6  | AE  | B6  | BE  |
| disp32[EDI]    |    |  111  | 87  | 8F  | 97  | 9F  | A7  | AF  | B7  | BF  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| EAX/AX/AL      | 11  |  000  | C0  | C8  | D0  | D8  | E0  | E8  | F0  | F8  |
| ECX/CX/CL      |    |  001  | C1  | C9  | D1  | D9  | E1  | E9  | F1  | F9  |
| EDX/DX/DL      |    |  010  | C2  | CA  | D2  | DA  | E2  | EA  | F2  | FA  |
| EBX/BX/BL      |    |  011  | C3  | CB  | D3  | DB  | E3  | EB  | F3  | FB  |
| ESP/SP/AH      |    |  100  | C4  | CC  | D4  | DC  | E4  | EC  | F4  | FC  |
| EBP/BP/CH      |    |  101  | C5  | CD  | D5  | DD  | E5  | ED  | F5  | FD  |
| ESI/SI/DH      |    |  110  | C6  | CE  | D6  | DE  | E6  | EE  | F6  | FE  |
| EDI/DI/BH      |    |  111  | C7  | CF  | D7  | DF  | E7  | EF  | F7  | FF  |
\-------------------------------------------------------------------------------/</pre>
'''Notes:'''
 
1.[--][--] means a SIB follows the ModR/M byte.
 
2.'''disp8'''denotes an 8-bit displacement following the SIB byte, to be sign- extended and added to the index.
 
'''disp32'''denotes a 32-bit displacement following the SIB byte, to be added to the index. <br />
 
[[[00804.htm|prev]]][[[00806.htm|next]]][[[00802.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== 32-Bit Addressing Forms with the SIB Byte ===
 
<br />
 
<pre>/-------------------------------------------------------------------------------\
|                              | EAX | ECX | EDX | EBX | ESP | [*] | ESI | EDI |
| r32                          | 0  | 1  | 2  | 3  | 4  | 5  | 6  | 7  |
| Base =                        | 000 | 001 | 010 | 011 | 100 | 101 | 110 | 111 |
| Base =                        |    |    |    |    |    |    |    |    |
|-------------------------------+-----------------------------------------------|
| Scaled Index    | SS  | Index |          SIB Values in Hexadecimal          |
|-----------------+-----+-------+-----------------------------------------------|
| [EAX]          | 00  |  000  | 00  | 01  | 02  | 03  | 04  | 05  | 06  | 07  |
| [ECX]          |    |  001  | 08  | 09  | 0A  | 0B  | 0C  | 0D  | 0E  | 0F  |
| [EDX]          |    |  010  | 10  | 11  | 12  | 13  | 14  | 15  | 16  | 17  |
| [EBX]          |    |  011  | 18  | 19  | 1A  | 1B  | 1C  | 1D  | 1E  | 1F  |
| none            |    |  100  | 20  | 21  | 22  | 23  | 24  | 25  | 26  | 27  |
| [EBP]          |    |  101  | 28  | 29  | 2A  | 2B  | 2C  | 2D  | 2E  | 2F  |
| [ESI]          |    |  110  | 30  | 31  | 32  | 33  | 34  | 35  | 36  | 37  |
| [EDI]          |    |  111  | 38  | 39  | 3A  | 3B  | 3C  | 3D  | 3E  | 3F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| [EAX*2]        | 01  |  000  | 40  | 41  | 42  | 43  | 44  | 45  | 46  | 47  |
| [ECX*2]        |    |  001  | 48  | 49  | 4A  | 4B  | 4C  | 4D  | 4E  | 4F  |
| [EDX*2]        |    |  010  | 50  | 51  | 52  | 53  | 54  | 55  | 56  | 57  |
| [EBX*2]        |    |  011  | 58  | 59  | 5A  | 5B  | 5C  | 5D  | 5E  | 5F  |
| none            |    |  100  | 60  | 61  | 62  | 63  | 64  | 65  | 66  | 67  |
| [EBP*2]        |    |  101  | 68  | 69  | 6A  | 6B  | 6C  | 6D  | 6E  | 6F  |
| [ESI*2]        |    |  110  | 70  | 71  | 72  | 73  | 74  | 75  | 76  | 77  |
| [EDI*2]        |    |  111  | 78  | 79  | 7A  | 7B  | 7C  | 7D  | 7E  | 7F  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| [EAX*4]        | 10  |  000  | 80  | 81  | 82  | 83  | 84  | 85  | 86  | 87  |
| [ECX*4]        |    |  001  | 88  | 89  | 8A  | 8B  | 8C  | 8D  | 8E  | 8F  |
| [EDX*4]        |    |  010  | 90  | 91  | 92  | 93  | 94  | 95  | 96  | 97  |
| [EBX*4]        |    |  011  | 98  | 89  | 9A  | 9B  | 9C  | 9D  | 9E  | 9F  |
| none            |    |  100  | A0  | A1  | A2  | A3  | A4  | A5  | A6  | A7  |
| [EBP*4]        |    |  101  | A8  | A9  | AA  | AB  | AC  | AD  | AE  | AF  |
| [ESI*4]        |    |  110  | B0  | B1  | B2  | B3  | B4  | B5  | B6  | B7  |
| [EDI*4]        |    |  111  | B8  | B9  | BA  | BB  | BC  | BD  | BE  | BF  |
|-----------------+-----+-------+-----+-----+-----+-----+-----+-----+-----+-----|
| [EAX*8]        | 11  |  000  | C0  | C1  | C2  | C3  | C4  | C5  | C6  | C7  |
| [ECX*8]        |    |  001  | C8  | C9  | CA  | CB  | CC  | CD  | CE  | CF  |
| [EDX*8]        |    |  010  | D0  | D1  | D2  | D3  | D4  | D5  | D6  | D7  |
| [EBX*8]        |    |  011  | D8  | D9  | DA  | DB  | DC  | DD  | DE  | DF  |
| none            |    |  100  | E0  | E1  | E2  | E3  | E4  | E5  | E6  | E7  |
| [EBP*8]        |    |  101  | E8  | E9  | EA  | EB  | EC  | ED  | EE  | EF  |
| [ESI*8]        |    |  110  | F0  | F1  | F2  | F3  | F4  | F5  | F6  | F7  |
| [EDI*8]        |    |  111  | F8  | F9  | FA  | FB  | FC  | FD  | FE  | FF  |
\-------------------------------------------------------------------------------/</pre>
'''Notes:'''
 
[*] means a disp32 with no base if MOD is 00, [EBP] otherwise. This provides the following addressing modes: <br />
 
<pre>disp32[index]          (MOD=00)
disp8[EBP][index]      (MOD=01)
disp32[EBP][index]      (MOD=10)</pre>
[[[00805.htm|prev]]][[[00807.htm|next]]][[[00796.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== How to Read the Instruction Set Pages ===
 
The following sections describe how to interpret the description pages for each instruction listed in the [[01466.htm|Intel Instruction Set]]section. Each instruction family is introduced by a descriptive heading such as the following:
 
'''CMC-Complement Carry Flag'''
 
Each instruction family may be accompanied by descriptive sections labeled as follows: [[00807.htm|Details Table]], [[00854.htm|Operation]], [[00855.htm|Flags Affected]], [[00858.htm|Protected Mode Exceptions]], [[00859.htm|Real Address Mode Exceptions]], [[00860.htm|Virtual-8086 Mode Exceptions]], and optionally, a '''Notes'''section. The following sections explain the notational conventions and abbreviations used in these paragraphs of the instruction descriptions.
 
[[[00806.htm|prev]]][[[00808.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
For each instruction family, a table is given to list the details of each individual instruction. The following is an example of this table: <br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|F5        |CMC                |2|2|2|2|2|2|Complement carry flag            |
\------------------------------------------------------------------------------/</pre>
The [[00808.htm|Encoding]], [[00809.htm|Instruction]], and [[00852.htm|Description]]columns are described in the following sections. The columns labeled '''0, 1, 2, 3, 4,'''and '''5'''are collectively described in the [[00851.htm|Clocks]]section. A timing entry appearing in one of these columns is an indication that the associated processor implements that particular instruction variation. The column names are abbreviated, and are described as follows:
 
0The 8088/8086/8087 Processor Family
 
1The 80186/8087 Processor Family
 
2The 80286/80287 Processor Family
 
3The 80386/80387 Processor Family
 
4The 80486 Processor Family
 
5The Pentium Processor Family <br />
 
[[[00807.htm|prev]]][[[00809.htm|next]]][[[00807.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Encoding Column ===
 
The &quot;Encoding&quot; column gives the complete object code produced for each form of the instruction. When possible, the codes are given as hexadecimal bytes , in the same order in which they appear in memory. Definitions of entries other than hexadecimal bytes are as follows:
 
�'''/digit:'''(digit is between 0 and 7) indicates that the ModR/M byte of the instruction uses only the r/m (register or memory) operand. The '''reg'''field contains the digit that provides an extension to the instruction's opcode.
 
�'''/r:'''indicates that the ModR/M byte of the instruction contains both a register operand and an r/m operand.
 
�'''cb, cw, cd, cp:'''a 1-byte (cb), 2-byte (cw), 4-byte (cd) or 6-byte (cp) value following the opcode that is used to specify a code offset and possibly a new value for the code segment register.
 
�'''ib, iw, id:'''a 1-byte (ib), 2-byte (iw), or 4-byte (id) immediate operand to the instruction that follows the opcode, ModR/M bytes or scale-indexing bytes. The opcode determines if the operand is a signed value. All words and doublewords are given with the low-order byte first.
 
�'''+rb, +rw, +rd:'''a register code, from 0 through 7, added to the hexadecimal byte given at the left of the plus sign to form a single opcode byte. The codes are-
 
<br />
 
<pre>/--------------------------------------------------------------\
| rb                | rw                | rd                |
|--------------------+--------------------+--------------------|
|AL  =  0          |AX  =  0          |EAX  =  0          |
|--------------------+--------------------+--------------------|
|CL  =  1          |CX  =  1          |ECX  =  1          |
|--------------------+--------------------+--------------------|
|DL  =  2          |DX  =  2          |EDX  =  2          |
|--------------------+--------------------+--------------------|
|BL  =  3          |BX  =  3          |EBX  =  3          |
|--------------------+--------------------+--------------------|
|AH  =  4          |SP  =  4          |ESP  =  4          |
|--------------------+--------------------+--------------------|
|CH  =  5          |BP  =  5          |EBP  =  5          |
|--------------------+--------------------+--------------------|
|DH  =  6          |SI  =  6          |ESI  =  6          |
|--------------------+--------------------+--------------------|
|BH  =  7          |DI  =  7          |EDI  =  7          |
\--------------------------------------------------------------/</pre>
�'''+i:'''used in floating-point instructions when one of the operands is ST(i) from the FPU register stack. The number i (which can range from 0 to 7) is added to the hexadecimal byte given at the left of the plus sign to form a single opcode byte. <br />
 
[[[00808.htm|prev]]][[[00810.htm|next]]][[[00807.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Column ===
 
The &quot;Instruction&quot; column gives the syntax of the instruction statement as it would appear in an assembler program. The following is a list of the symbols used to represent operands in the instruction statements:
 
[[[00809.htm|prev]]][[[00811.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== rel8 ===
 
A relative address in the range from 128 bytes before the end of the instruction to 127 bytes after the end of the instruction.
 
[[[00810.htm|prev]]][[[00812.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== rel16 ===
 
A relative address in the range from 32768 bytes before the end of the instruction to 32767 bytes after the end of the instruction. Applies to instructions with an operand-size attribute of 16 bits, and must be within the same code segment as the instruction assembled.
 
[[[00811.htm|prev]]][[[00813.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== rel32 ===
 
A relative address in the range from 2147483648 bytes before the end of the instruction to 2147483647 bytes after the end of the instruction. Applies to instructions with an operand-size attribute of 32 bits, and must be within the same code segment as the instruction assembled.
 
[[[00812.htm|prev]]][[[00814.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ptr16:16 ===
 
A far pointer, typically in a code segment different from that of the instruction. The notation '''16:16'''indicates that the value of the pointer has two parts. The value to the left of the colon is a 16-bit selector or value destined for the code segment register. The value to the right reflects the operand-size attribute of the instruction (16 bits) and corresponds to the offset within the destination segment.
 
[[[00813.htm|prev]]][[[00815.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ptr16:32 ===
 
A far pointer, typically in a code segment different from that of the instruction. The notation '''16:32'''indicates that the value of the pointer has two parts. The value to the left of the colon is a 16-bit selector or value destined for the code segment register. The value to the right reflects the operand-size attribute of the instruction (32 bits) and corresponds to the offset within the destination segment.
 
[[[00814.htm|prev]]][[[00816.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r8 ===
 
One of the byte registers AL, CL, DL, BL, AH, CH, DH, or BH.
 
[[[00815.htm|prev]]][[[00817.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r16 ===
 
One of the word registers AX, CX, DX, BX, SP, BP, SI, or DI.
 
[[[00816.htm|prev]]][[[00818.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r32 ===
 
One of the doubleword registers EAX, ECX, EDX, EBX, ESP, EBP, ESI, or EDI.
 
[[[00817.htm|prev]]][[[00819.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== imm8 ===
 
An immediate byte value. '''imm8'''is a signed number between -128 and +127 inclusive. For instructions in which '''imm8'''is combined with a word or doubleword operand, the immediate value is sign-extended to form a word or doubleword. The upper byte of the word is filled with the topmost bit of the immediate value.
 
[[[00818.htm|prev]]][[[00820.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== imm16 ===
 
An immediate word value used for instructions whose operand-size attribute is 16 bits. This is a number between -32768 and +32767 inclusive.
 
[[[00819.htm|prev]]][[[00821.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== imm32 ===
 
An immediate doubleword value used for instructions whose operand-size attribute is 32-bits. It allows the use of a number between +2147483647 and -2147483648 inclusive.
 
[[[00820.htm|prev]]][[[00822.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r/m8 ===
 
A one-byte operand that is either the contents of a byte register (AL, BL, CL, DL, AH, BH, CH, DH), or a byte from memory.
 
[[[00821.htm|prev]]][[[00823.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r/m16 ===
 
A word register or memory operand used for instructions whose operand-size attribute is 16 bits. The word registers are: AX, BX, CX, DX, SP, BP, SI, DI. The contents of memory are found at the address provided by the effective address computation.
 
[[[00822.htm|prev]]][[[00824.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r/m32 ===
 
A doubleword register or memory operand used for instructions whose operand-size attribute is 32-bits. The doubleword registers are: EAX, EBX, ECX, EDX, ESP, EBP, ESI, EDI. The contents of memory are found at the address provided by the effective address computation.
 
[[[00823.htm|prev]]][[[00825.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== r/m64 ===
 
A quadword register or memory operand used for instructions whose operand- size attribute is 64-bits. The reg/opcode field represents the opcode. The contents of memory are found at the address provided by the effective address computation.
 
[[[00824.htm|prev]]][[[00826.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m ===
 
A 16 or 32-bit memory operand.
 
[[[00825.htm|prev]]][[[00827.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m8 ===
 
A memory byte addressed by DS:[E]SI or ES:[E]DI (used only by string instructions).
 
[[[00826.htm|prev]]][[[00828.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16 ===
 
A memory word addressed by DS:[E]SI or ES:[E]DI (used only by string instructions).
 
[[[00827.htm|prev]]][[[00829.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m32 ===
 
A memory doubleword addressed by DS:[E]SI or ES:[E]DI (used only by string instructions).
 
[[[00828.htm|prev]]][[[00830.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16:16 ===
 
A memory operand containing a far pointer composed of two numbers. The number to the left of the colon corresponds to the pointer's segment selector. The number to the right corresponds to its offset.
 
[[[00829.htm|prev]]][[[00831.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16:32 ===
 
A memory operand containing a far pointer composed of two numbers. The number to the left of the colon corresponds to the pointer's segment selector. The number to the right corresponds to its offset.
 
[[[00830.htm|prev]]][[[00832.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16&amp;16 ===
 
A memory operand consisting of data item pairs whose sizes are indicated on the left and the right side of the ampersand. All memory addressing modes are allowed. Used by the BOUND instruction to provide an operand containing an upper and lower bounds for array indices.
 
[[[00831.htm|prev]]][[[00833.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16&amp;32 ===
 
A memory operand consisting of data item pairs whose sizes are indicated on the left and the right side of the ampersand. All memory addressing modes are allowed. Used by the by LIDT and LGDT to provide a word with which to load the limit field, and a doubleword with which to load the base field of the corresponding Global and Interrupt Descriptor Table Registers.
 
[[[00832.htm|prev]]][[[00834.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m32&amp;32 ===
 
A memory operand consisting of data item pairs whose sizes are indicated on the left and the right side of the ampersand. All memory addressing modes are allowed. Used by the BOUND instruction to provide an operand containing an upper and lower bounds for array indices.
 
[[[00833.htm|prev]]][[[00835.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== moffs8 ===
 
The memory offset of a BYTE variable used in some variants of the MOV instruction. The actual address is given by a simple offset relative to the segment base. No ModR/M byte is used in the instruction. The address- size attribute of the instruction determines the size of the offset data.
 
[[[00834.htm|prev]]][[[00836.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== moffs16 ===
 
The memory offset of a WORD variable used in some variants of the MOV instruction. The actual address is given by a simple offset relative to the segment base. No ModR/M byte is used in the instruction. The address- size attribute of the instruction determines the size of the offset data.
 
[[[00835.htm|prev]]][[[00837.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== moffs32 ===
 
The memory offset of a DWORD variable used in some variants of the MOV instruction. The actual address is given by a simple offset relative to the segment base. No ModR/M byte is used in the instruction. The address- size attribute of the instruction determines the size of the offset data.
 
[[[00836.htm|prev]]][[[00838.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Sreg ===
 
A segment register. The segment register bit assignments are ES=0, CS=1, SS=2, DS=3, FS=4, and GS=5.
 
[[[00837.htm|prev]]][[[00839.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m32real ===
 
A single-precision floating-point operand in memory.
 
[[[00838.htm|prev]]][[[00840.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m64real ===
 
A double-precision floating-point operand in memory.
 
[[[00839.htm|prev]]][[[00841.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m80real ===
 
An extended-precision floating-point operand in memory.
 
[[[00840.htm|prev]]][[[00842.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m80bcd ===
 
A 80 byte binary-coded decimal operand in memory.
 
[[[00841.htm|prev]]][[[00843.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m16int ===
 
A word integer operand in memory. Used in some floating-point instructions.
 
[[[00842.htm|prev]]][[[00844.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m32int ===
 
A short integer operand in memory. Used in some floating-point instructions.
 
[[[00843.htm|prev]]][[[00845.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m64int ===
 
A long integer operand in memory. Used in some floating-point instructions.
 
[[[00844.htm|prev]]][[[00846.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m14byte ===
 
A 14-byte floating-point operand in memory.
 
[[[00845.htm|prev]]][[[00847.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m28byte ===
 
A 28-byte floating-point operand in memory.
 
[[[00846.htm|prev]]][[[00848.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m94byte ===
 
A 94-byte floating-point operand in memory.
 
[[[00847.htm|prev]]][[[00849.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== m108byte ===
 
A 108-byte floating-point operand in memory.
 
[[[00848.htm|prev]]][[[00850.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ST or ST(0) ===
 
Top element of the FPU register stack.
 
[[[00849.htm|prev]]][[[00851.htm|next]]][[[00809.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ST(i) ===
 
ith element from the top of the FPU register stack. (i=0..7)
 
[[[00850.htm|prev]]][[[00852.htm|next]]][[[00807.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Clocks Columns ===
 
Each &quot;Clocks&quot; column gives the approximate number of clock cycles the instruction takes to execute on that particular processor. The clock count calculations makes the following assumptions:
 
�Data and instruction accesses hit in the cache.
 
�The target of a jump instruction is in the cache.
 
�No invalidate cycles contend with the instruction for use of the cache.
 
�Page translation hits in the TLB.
 
�Memory operands are aligned.
 
�Effective address calculations use a base register which is not the destination register of the preceding instruction.
 
�No exceptions are detected during execution.
 
�There are no write-buffer delays. <br />
 
The following symbols are used in the clock count specifications:
 
�'''n,'''which represents a number of repetitions.
 
�'''m,'''which represents the number of components in the next instruction executed, where the entire displacement (if any) counts as one component, the entire immediate data (if any) counts as one component, and every other byte of the instruction and prefix(es) each counts as one component.
 
�'''pm:,'''a clock count that applies when the instruction executes in Protected Mode. '''pm:'''is not given when the clock counts are the same for Protected and Real Address Modes. <br />
 
When an exception occurs during the execution of an instruction and the exception handler is in another task, the instruction execution time is increased by the number of clocks to effect a task switch. This parameter depends on several factors:
 
�The type of TSS used to represent the new task (32 bit TSS or 16 bit TSS).
 
�Whether the current task is in V86 mode.
 
�Whether the new task is in V86 mode.
 
�Whether accesses hit in the cache.
 
�Whether a task gate on an interrupt/trap gate is used. <br />
 
The following table summarizes the task switch times for exceptions, assuming cache hits and the use of task gates.
 
'''Task Switch Times for Exceptions'''<br />
 
<pre>/------------------------------------------------------------------------------\
|            OLD TASK          |                  NEW TASK                  |
|                              |----------------------------------------------|
|                              | TO 32 BIT TSS | TO 16 BIT TSS |  TO VM TSS  |
|-------------------------------+---------------+---------------+--------------|
|      VM/32 bit/16 bit TSS    |      85      |      87      |      71      |
\------------------------------------------------------------------------------/</pre>
[[[00851.htm|prev]]][[[00853.htm|next]]][[[00807.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description Column ===
 
The &quot;Description&quot; column following the &quot;Clocks&quot; columns briefly explains the various forms of the instruction. The &quot;Operation&quot; and &quot;Description&quot; sections contain more details of the instruction's operation.
 
[[[00852.htm|prev]]][[[00854.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The &quot;Description&quot; section contains further explanation of the instruction's operation.
 
[[[00853.htm|prev]]][[[00855.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
The &quot;Operation&quot; section contains an algorithmic description of the instruction which uses a notation similar to the Algol or Pascal language. The algorithms are composed of the following elements:
 
�Comments are enclosed within the symbol pairs &quot;(*&quot; and &quot;*)&quot;.
 
�Compound statements are enclosed between the keywords of the &quot;if&quot; statement (IF, THEN, ELSE, FI) or of the &quot;do&quot; statement (DO, OD), or of the &quot;case&quot; statement (CASE ... OF, ESAC).
 
�Execution continues until the END statement is encountered.
 
�A register name implies the contents of the register. A register name enclosed in brackets implies the contents of the location whose address is contained in that register. For example, ES:[DI] indicates the contents of the location whose ES segment relative address is in register DI. [SI] indicates the contents of the address contained in register SI relative to SI's default segment (DS) or overridden segment.
 
�Brackets are also used for memory operands, where they mean that the contents of the memory location is a segment-relative offset. For example, [SRC] indicates that the contents of the source operand is a segment- relative offset.
 
�A � B; indicates that the value of B is assigned to A.
 
�The symbols =, &lt;&gt;, ò, and ó are relational operators used to compare two values, meaning equal, not equal, greater or equal, less or equal, respectively. A relational expression such as A = B is TRUE if the value of A is equal to B; otherwise it is FALSE.
 
�A * B indicates that the value of A is multiplied by the value of B. <br />
 
The following identifiers are used in the algorithmic descriptions:
 
�'''OperandSize'''represents the operand-size attribute of the instruction, which is either 16 or 32 bits. '''AddressSize'''represents the address-size attribute, which is either 16 or 32 bits. For example,
 
<br />
 
<pre>IF instruction = CMPSW
THEN OperandSize � 16;
ELSE
  IF instruction = CMPSD
  THEN OperandSize � 32;
  FI;
FI;</pre>
indicates that the operand-size attribute depends on the form of the CMPS instruction used. Refer to the explanation of address-size and operand-size attributes at the beginning of this chapter for general guidelines on how these attributes are determined.
 
�'''StackAddrSize'''represents the stack address-size attribute associated with the instruction, which has a value of 16 or 32 bits, as explained earlier in the chapter.
 
�'''SRC'''represents the source operand. When there are two operands, SRC is the one on the right.
 
�'''DEST'''represents the destination operand. When there are two operands, DEST is the one on the left.
 
�'''LeftSRC, RightSRC'''distinguishes between two operands when both are source operands.
 
�'''eSP'''represents either the SP register or the ESP register depending on the setting of the B-bit for the current stack segment. <br />
 
The following functions are used in the algorithmic descriptions:
 
�'''Truncate to 16 bits(value)'''reduces the size of the value to fit in 16 bits by discarding the uppermost bits as needed.
 
�'''Addr(operand)'''returns the effective address of the operand (the result of the effective address calculation prior to adding the segment base).
 
�'''ZeroExtend(value)'''returns a value zero-extended to the operand-size attribute of the instruction. For example, if OperandSize = 32, ZeroExtend of a byte value of -10 converts the byte from F6H to doubleword with hexadecimal value 000000F6H. If the value passed to ZeroExtend and the operand-size attribute are the same size, ZeroExtend returns the value unaltered.
 
�'''SignExtend(value)'''returns a value sign-extended to the operand-size attribute of the instruction. For example, if OperandSize = 32, SignExtend of a byte containing the value -10 converts the byte from F6H to a doubleword with hexadecimal value FFFFFFF6H. If the value passed to SignExtend and the operand-size attribute are the same size, SignExtend returns the value unaltered.
 
�'''Push(value)'''pushes a value onto the stack. The number of bytes pushed is determined by the operand-size attribute of the instruction. The action of Push is as follows: <br />
 
<pre>IF StackAddrSize = 16
THEN
  IF OperandSize = 16
  THEN
      SP � SP -2;
      SS:[SP] � value; (* 2 bytes assigned starting at byte address in SP *)
  ELSE (* OperandSize = 32 *)
      SP � SP -4;
      SS:[SP] � value; (* 4 bytes assigned starting at byte address in SP *)
  FI;
ELSE (* StackAddrSize = 32 *)
  IF OperandSize = 16
  THEN
  ESP � ESP -2;
      SS:[ESP] � value; (* 2 bytes assigned starting at byte address in ESP*)
  ELSE (* OperandSize = 32 *)
      ESP � ESP -4;
      SS:[ESP] � value; (* 4 bytes assigned starting at byte address in ESP*)
  FI;
FI;</pre>
�'''Pop(value)'''removes the value from the top of the stack and returns it. The statement EAX � Pop( ); assigns to EAX the 32-bit value that Pop took from the top of the stack. Pop will return either a word or a doubleword depending on the operand-size attribute. The action of Pop is as follows: <br />
 
<pre>IF StackAddrSize = 16
THEN
  IF OperandSize = 16
  THEN
      ret val � SS:[SP]; (* 2-byte value *)
      SP � SP + 2;
  ELSE (* OperandSize = 32 *)
      ret val � SS:[SP]; (* 4-byte value *)
      SP � SP + 4;
  FI;
ELSE (* StackAddrSize = 32 *)
  IF OperandSize = 16
  THEN
      ret val � SS:[ESP]; (* 2 byte value *)
      ESP � ESP + 2;
  ELSE (* OperandSize = 32 *)
      ret val � SS:[ESP]; (* 4 byte value *)
      ESP � ESP + 4;
  FI;
FI;
RETURN(ret val); (*returns a word or doubleword*)</pre>
Pop ST is used on floating-point instruction pages to mean ''pop the FPU register stack''.
 
�'''Bit[BitBase, BitOffset]'''returns the value of a bit within a bit string, which is a sequence of bits in memory or a register. Bits are numbered from low-order to high-order within registers and within memory bytes. In memory , the two bytes of a word are stored with the low-order byte at the lower address.
 
If the base operand is a register, the offset can be in the range 0..31. This offset addresses a bit within the indicated register. An example, 'BIT [EAX, 21]' is illustrated in the following figure. <br />
 
<pre>Bit Offset for BIT[EAX,21]
 
/------------------------------------------------------\
|    31            21                            0    |
|  /----------------------------------------------\  |
|  \----------------------------------------------/  |
|                    �                            �  |
|                    |                            |  |
|                    \--------BITOFFSET=21---------/  |
|                                                      |
\------------------------------------------------------/</pre>
If BitBase is a memory address, BitOffset can range from -2 gigabits to 2 gigabits. The addressed bit is numbered (Offset MOD 8) within the byte at address (BitBase + (BitOffset DIV 8)), where DIV is signed division with rounding towards negative infinity, and MOD returns a positive number. This is illustrated in the following figure. <br />
 
<pre>Memory Bit Indexing
 
/------------------------------------------------------\
|  7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0    |
|  /----------------------------------------------\  |
|  \----------------------------------------------/  |
|  |  BITBASE+1  |    BITBASE    |  BITBASE-1  |  |
|      �                          |                  |
|      \------OFFSET=+13-----------/                  |
|                                                      |
|                                                      |
|  7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0    |
|  /----------------------------------------------\  |
|  \----------------------------------------------/  |
|  |  BITBASE    |  BITBASE-1    |  BITBASE-2  |  |
|                  |                      �            |
|                  \-----OFFSET=-11-------/            |
|                                                      |
\------------------------------------------------------/</pre>
�'''I-O-Permission(I-O-Address, width)'''returns TRUE or FALSE depending on the I/O permission bitmap and other factors. This function is defined as follows: <br />
 
<pre>IF TSS type is 16-bit THEN RETURN FALSE; FI;
Ptr� [TSS+66]; (* fetch bitmap pointer *)
BitStringAddr � SHR (I-O-Address, 3) + Ptr;
MaskShift � I-O-Address AND 7;
CASE width OF:
  BYTE: nBitMask � 1;
  WORD: nBitMask � 3;
  DWORD: nBitMask � 15;
ESAC;
mask � SHL (nBitMask, MaskShift);
CheckString � [BitStringAddr] AND mask;
IF CheckString = 0
THEN RETURN (TRUE);
ELSE RETURN (FALSE);
FI;</pre>
�'''Switch-Tasks'''is described in detail in the Intel documentation. <br />
 
[[[00854.htm|prev]]][[[00856.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
Pages describing basic instructions have a &quot;Flags Affected&quot; section the contains a flags information table similar to the following: <br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|0 |  |  |* |* |? |* |0 |
\-----------------------/</pre>
The first row of the table lists the mnemonic identifiers for the various flags. The entries in the second row are filled in according to how the flag is affected by the instruction: <br />
 
<pre>/-----------------------------------------\
|VALUE  |MEANING                        |
|--------+--------------------------------|
|&lt;blank&gt; |Instruction does not affect flag|
|--------+--------------------------------|
|0      |Instruction clears the flag    |
|--------+--------------------------------|
|1      |Instruction sets the flag      |
|--------+--------------------------------|
|?      |Instruction's effect on the flag|
|        |is undefined                    |
|--------+--------------------------------|
|*      |Instruction modifies the flag  |
|        |(either sets or clears depending|
|        |on operands)                    |
\-----------------------------------------/</pre>
The following table lists the mnemonic identifier, full name, and purpose of the flags that are applicable to all processor families and that are are most commonly used from within application-level programs. Not all flags are included in this table; see the Intel documentation for a more complete description of flag usage from within systems-level programs. <br />
 
<pre>/--------------------------------------------------------------------------------\
|MNEMONIC|FLAG NAME      |PURPOSE                                              |
|--------+----------------+------------------------------------------------------|
|OF      |Overflow        |Result exceeds positive or negative limit of number  |
|        |                |range                                                |
|--------+----------------+------------------------------------------------------|
|DF      |Direction      |Setting the DF flag causes string instructions to    |
|        |                |auto-decrement, that is, to process strings from high |
|        |                |addresses.  Clearing the DF flag causes string        |
|        |                |instructions to auto-increment, or to process strings |
|        |                |from low addresses to high addresses.                |
|--------+----------------+------------------------------------------------------|
|IF      |Interrupt Enable|Controls the acceptance of external interrupts        |
|        |                |signalled via the INTR pin.                          |
|--------+----------------+------------------------------------------------------|
|SF      |Sign            |Result is negative (less than zero)                  |
|--------+----------------+------------------------------------------------------|
|ZF      |Zero            |Result is zero                                        |
|--------+----------------+------------------------------------------------------|
|AF      |Auxiliary carry |Carry out of bit position 3 (used for BCD)            |
|--------+----------------+------------------------------------------------------|
|PF      |Parity          |Low byte of result has even parity (even number of set|
|        |                |bits)                                                |
|--------+----------------+------------------------------------------------------|
|CF      |Carry          |Carry out of most significant bit of result          |
\--------------------------------------------------------------------------------/</pre>
The flags information table is usually followed by a paragraph description of how the flags are affected:
 
�If a flag is always cleared or always set by the instruction, the value is given (0 or 1) after the flag name. Arithmetic and logical instructions usually assign values to the status flags in a uniform manner. Nonconventional assignments are described in the [[00854.htm|Operation]]section.
 
�The values of flags listed as &quot;undefined&quot; may be changed by the instruction in an indeterminate manner. <br />
 
All flags not listed are unchanged by the instruction.
 
[[[00855.htm|prev]]][[[00857.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FPU Flags Affected ===
 
The floating-point instruction pages have a section called &quot;FPU Flags Affected,&quot; which tells how each instruction can affect the four condition code bits of the FPU status word. These pages contain a condition code information table similar to the following: <br />
 
<pre>/-----------\
|C0|C1|C2|C3|
|--+--+--+--|
|? |* |? |? |
\-----------/</pre>
The first row of the table lists the names of the floating-point condition code flags. The entries in the second row are filled in according to how the flag is affected by the instruction: <br />
 
<pre>/-----------------------------------------\
|VALUE  |MEANING                        |
|--------+--------------------------------|
|&lt;blank&gt; |Instruction does not affect flag|
|--------+--------------------------------|
|0      |Instruction clears the flag    |
|--------+--------------------------------|
|1      |Instruction sets the flag      |
|--------+--------------------------------|
|?      |Instruction's effect on the flag|
|        |is undefined                    |
|--------+--------------------------------|
|*      |Instruction modifies the flag  |
|        |(either sets or clears depending|
|        |on operands)                    |
\-----------------------------------------/</pre>
The four FPU condition code bits (C0, C1, C2, and C3) are similar to the flags in a CPU; the processor updates these bits to reflect the outcome of arithmetic operations. The effect of these instructions on the condition code bits is summarized in the following table:
 
'''Condition Code Interpretation'''<br />
 
<pre>/------------------------------------------------------------------------------\
| INSTRUCTION            |      C0    |    C3    |    C2    |    C1    |
|-------------------------+--------------------------+------------+------------|
| FCOM, FCOMP, FCOMPP,    |  Result of Comparison  | Operands  | Zero or    |
| FTST, FUCOMPP, FICOM,  |                          | is not    | O/U#      |
| FICOMP                  |                          | Comparable |            |
|-------------------------+---------------------------------------+------------|
| FXAM                    |            Operand class            | Sign or    |
|                        |                                      | O/U#      |
|-------------------------+---------------------------------------+------------|
| FPREM, FPREM1          |      Q2    |    Q1    | 0=reduction| Q0 or O/U# |
|                        |            |            |  complete  |            |
|                        |            |            |            |            |
|                        |            |            | 1=reduction|            |
|                        |            |            | incomplete |            |
|-------------------------+---------------------------------------+------------|
| FIST, FBSTP, FRINDINT,  |              UNDEFINED              | Roundup or |
| FST, FSTP, FADD, FMUL,  |                                      | O/U#      |
| FDIV, FDIVR, FSUB,      |                                      |            |
| FSUBR, FSCALE, FSQRT,  |                                      |            |
| FPATAN, F2XM1, FYL2X,  |                                      |            |
| FYL2XP1                |                                      |            |
|-------------------------+---------------------------------------+------------|
| FPTAN, FSIN, FCOS,      |        UNDEFINED        | 0=reduction| Roundup or |
| FSINCOS                |                          | complete  | O/U#      |
|                        |                          |            | (UNDEFINED |
|                        |                          | 1=reduction| if C2=1)  |
|                        |                          | incomplete |            |
|-------------------------+---------------------------------------+------------|
| FCHS, FABS, FXCH,      |              UNDEFINED              | Zero or    |
| FINCSTP, FDECSTP, Con-  |                                      | O/U#      |
| stant Loads, FXTRACT,  |                                      |            |
| FLD, FILD, FBLD, FSTP  |                                      |            |
| (ext. real)            |                                      |            |
|-------------------------+----------------------------------------------------|
| FLDENV, FRSTOR          |            Each bit loaded from memory            |
|-------------------------+----------------------------------------------------|
| FLDCW, FSTENV, FSTCW,  |                      UNDEFINED                    |
| FSTSW, FCLEX            |                                                    |
|-------------------------+----------------------------------------------------|
| FINIT, FSAVE            |    Zero    |    Zero    |    Zero    |    Zero    |
\------------------------------------------------------------------------------/</pre>
'''NOTES:'''
 
'''O/U#'''When both IE and SF bits of status word are set, this bit distinguishes between stack overflow (C1=1) and underflow (C1=0).
 
'''Reduction'''If FPREM and FPREM1 produces a remainder that is less than the modulus, reduction is complete. When reduction is incomplete the value at the top of the stack is a parial remainder, which can be used as input to further reduction. For FPTAN, FSIN, FCOS and FSINCOS, the reduction bit is set if the operand at the top of the stack is too large. In this case, the original operand remains at the top of the stack.
 
'''Roundup'''When the PE bit of the status word is set, this bit indicates whether the last rounding in the instruction was upward.
 
'''UNDEFINED'''Do not rely on any specific value in these bits. <br />
 
The condition code bits are used primarily for conditional branching. The FSTSW AX instruction stores the FPU status word directly into the AX register, allowing these condition codes to be inspected efficiently. The SAHF instruction can copy C3 - C0 directly to the CPU's flag bits to simplify conditional branching. The following table shows the mapping of these bits to the CPU flag bits. <br />
 
<pre>/-------------------------\
|FPU FLAG    |IU FLAG    |
|------------+------------|
|C0          |CF          |
|------------+------------|
|C1          |(None)      |
|------------+------------|
|C2          |PF          |
|------------+------------|
|C3          |ZF          |
\-------------------------/</pre>
[[[00856.htm|prev]]][[[00858.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Numeric Exceptions ===
 
For floating-point instruction pages, this section lists the exception flags of the FPU status word that each instruction can set. Exceptions are listed in abbreviated form, and are defined as follows:
 
ISInvalid operand due to stack overflow/underflow
 
IInvalid operand due to other cause
 
DDenormalized operand
 
ZDivide by zero
 
ONumeric overflow
 
UNumeric underflow
 
PInexact result (precision) <br />
 
[[[00857.htm|prev]]][[[00859.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
This section lists the exceptions that can occur when the instruction is executed in protected mode. The exception names are a pound sign (#) followed by two letters and an optional error code in parentheses. For example, #GP(0) denotes a general protection exception with an error code of 0. The following table associates each two-letter name with the corresponding interrupt number.
 
'''Exceptions'''<br />
 
<pre>/------------------------------------------------------------------------------\
|      MNEMONIC    |    INTERRUPT    |              DESCRIPTION            |
|-------------------+-------------------+--------------------------------------|
|        #UD        |        6        | Invalid opcode                      |
|        #NM        |        7        | Device not available                |
|        #DF        |        8        | Double fault                        |
|        #TS        |        10        | Invalid TSS                          |
|        #NP        |        11        | Segment or gate not present          |
|        #SS        |        12        | Stack fault                          |
|        #GP        |        13        | General protection fault            |
|        #PF        |        14        | Page fault                          |
|        #MF        |        16        | Floating-point error                |
|        #AC        |        17        | Alignment check                      |
\------------------------------------------------------------------------------/</pre>
Refer to the Intel documentation for a description of the exceptions and the processor state upon entry to the exception.
 
Application programmers should consult the documentation provided with their operating systems to determine the actions taken when exceptions occur.
 
[[[00858.htm|prev]]][[[00860.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Because less error checking is performed by the processor in Real Address Mode, this mode has fewer exception conditions. Refer to the Intel documentation for further information on these exceptions.
 
[[[00859.htm|prev]]][[[00861.htm|next]]][[[00806.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual-8086 Mode Exceptions ===
 
Virtual 8086 tasks provide the ability to simulate Virtual 8086 machines. Virtual 8086 Mode exceptions are similar to those for the 8086 processor, but there are some differences. Refer to the Intel documentation for complete information on Virtual Mode exceptions.
 
[[[00860.htm|prev]]][[[00862.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
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5+8*N
 
[[[01450.htm|prev]]][[[01452.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
5+9*N
 
[[[01451.htm|prev]]][[[01453.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
6*3,13*4
 
[[[01452.htm|prev]]][[[01454.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
6*3,13*4,13(E)CX*5
 
[[[01453.htm|prev]]][[[01455.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
6*3,9(E)CX*6
 
[[[01454.htm|prev]]][[[01456.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
6+11*N
 
[[[01455.htm|prev]]][[[01457.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
6+9*N
 
[[[01456.htm|prev]]][[[01458.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
7*3,7+3(E)CX*6
 
[[[01457.htm|prev]]][[[01459.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
7*3,8+4(E)CX*6
 
[[[01458.htm|prev]]][[[01460.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
7*3,9+4(E)CX*6
 
[[[01459.htm|prev]]][[[01461.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
8+8*N
 
[[[01460.htm|prev]]][[[01462.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
9+10*CX
 
[[[01461.htm|prev]]][[[01463.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
9+15*N
 
[[[01462.htm|prev]]][[[01464.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
9+17*CX
 
[[[01463.htm|prev]]][[[01465.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
9+22*N
 
[[[01464.htm|prev]]][[[01466.htm|next]]][[[00860.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Instruction Timing ===
 
N/A
 
[[[01465.htm|prev]]][[[01467.htm|next]]][[[00795.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Intel Instruction Set ===
 
The following section describes the individual processor instructions in detail.
 
[[[01466.htm|prev]]][[[01468.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
None
 
[[[01467.htm|prev]]][[[01469.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
None
 
[[[01468.htm|prev]]][[[01470.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
None
 
[[[01469.htm|prev]]][[[01471.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |  |
\-----------------------/</pre>
None
 
[[[01470.htm|prev]]][[[01472.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FPU Flags Affected ===
 
<br />
 
<pre>/-----------\
|C0|C1|C2|C3|
|--+--+--+--|
|? |* |? |? |
\-----------/</pre>
C1 as described in [[00856.htm|FPU Flags Affected]]; C0, C2, C3 undefined.
 
[[[01471.htm|prev]]][[[01473.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FPU Flags Affected ===
 
<br />
 
<pre>/-----------\
|C0|C1|C2|C3|
|--+--+--+--|
|? |? |? |? |
\-----------/</pre>
C0, C1, C2, C3 undefined.
 
[[[01472.htm|prev]]][[[01474.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FPU Flags Affected ===
 
<br />
 
<pre>/-----------\
|C0|C1|C2|C3|
|--+--+--+--|
|* |* |* |* |
\-----------/</pre>
C0, C1, C2, C3 as described in [[00856.htm|FPU Flags Affected]].
 
[[[01473.htm|prev]]][[[01475.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== FPU Flags Affected ===
 
<br />
 
<pre>/-----------\
|C0|C1|C2|C3|
|--+--+--+--|
|* |* |* |* |
\-----------/</pre>
C0, C1, C2, C3 as loaded.
 
[[[01474.htm|prev]]][[[01476.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== AAA-ASCII Adjust after Addition ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|37        |AAA                |X|X|X|X|X|X|ASCII adjust AL after addition    |
\------------------------------------------------------------------------------/</pre>
 
-----
 
Run the AAA instruction only following an ADD instruction that leaves a byte result in the AL register. The lower nibbles of the operands of the ADD instruction should be in the range 0 through 9 (BCD digits). In this case, the AAA instruction adjusts the AL register to contain the correct decimal digit result. If the addition produced a decimal carry, the AH register is incremented, and the CF and AF flags are set. If this same addition also produced FH in the upper nibble of AL then AH is incremented again. If there was no decimal carry, the CF and AF flags are cleared and the AH register is unchanged. In either case, the AL register is left with its top nibble set to 0. To convert the AL register to an ASCII result, follow the AAA instruction with OR AL, 30H.
 
 
-----
 
[[01477.htm|Description]]
 
[[01479.htm|Flags Affected]]
 
[[01478.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01475.htm|prev]]][[[01477.htm|next]]][[[01475.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|37        |AAA                |X|X|X|X|X|X|ASCII adjust AL after addition    |
\------------------------------------------------------------------------------/</pre>
[[[01476.htm|prev]]][[[01478.htm|next]]][[[01475.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Run the AAA instruction only following an ADD instruction that leaves a byte result in the AL register. The lower nibbles of the operands of the ADD instruction should be in the range 0 through 9 (BCD digits). In this case, the AAA instruction adjusts the AL register to contain the correct decimal digit result. If the addition produced a decimal carry, the AH register is incremented, and the CF and AF flags are set. If this same addition also produced FH in the upper nibble of AL then AH is incremented again. If there was no decimal carry, the CF and AF flags are cleared and the AH register is unchanged. In either case, the AL register is left with its top nibble set to 0. To convert the AL register to an ASCII result, follow the AAA instruction with OR AL, 30H.
 
[[[01477.htm|prev]]][[[01479.htm|next]]][[[01475.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>ALcarry � AL &gt; 0F9H; (* 1 if true *)
IF ((AL AND 0FH) &gt; 9) OR (AF = 1)
THEN
    AL � (AL + 6) AND 0FH;
    AH � AH + 1 + ALcarry;
    AF � 1;
    CF � 1;
ELSE
    AF � 0;
    CF � 0;
    AL � AL AND 0FH;
FI;</pre>
[[[01478.htm|prev]]][[[01480.htm|next]]][[[01475.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |? |? |* |? |* |
\-----------------------/</pre>
The AF and CF flags are set if there is a decimal carry, cleared if there is no decimal carry; the OF, SF, ZF, and PF flags are undefined.
 
[[[01479.htm|prev]]][[[01481.htm|next]]][[[01475.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01477.htm|Description]]
 
[[01479.htm|Flags Affected]]
 
[[01478.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01480.htm|prev]]][[[01482.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== AAD-ASCII Adjust AX before Division ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|D5 0A    |AAD                |X|X|X|X|X|X|ASCII adjust before division      |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The AAD instruction is used to prepare two unpacked BCD digits (the least- significant digit in the AL register, the most-significant digit in the AH register) for a division operation that will yield an unpacked result. This is accomplished by setting the AL register to AL+ (second byte of opcode * AH), and then clearing the AH register. The AX register is then equal to the binary equivalent of the original unpacked two-digit number.
 
 
-----
 
[[01483.htm|Description]]
 
[[01485.htm|Flags Affected]]
 
[[01484.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01481.htm|prev]]][[[01483.htm|next]]][[[01481.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|D5 0A    |AAD                |X|X|X|X|X|X|ASCII adjust before division      |
\------------------------------------------------------------------------------/</pre>
[[[01482.htm|prev]]][[[01484.htm|next]]][[[01481.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The AAD instruction is used to prepare two unpacked BCD digits (the least- significant digit in the AL register, the most-significant digit in the AH register) for a division operation that will yield an unpacked result. This is accomplished by setting the AL register to AL+ (second byte of opcode * AH), and then clearing the AH register. The AX register is then equal to the binary equivalent of the original unpacked two-digit number.
 
[[[01483.htm|prev]]][[[01485.htm|next]]][[[01481.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>regAL = AL;
regAH = AH;
AL � (regAH * imm8 + regAL) AND OFFH;
AH � 0;</pre>
'''Note:'''imm8 has the value of the instruction's second byte. The second byte under normally assembly of this instruction will be 0A, however, explicit modification of this byte will result in the operation described above and may alter results.
 
[[[01484.htm|prev]]][[[01486.htm|next]]][[[01481.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |* |* |? |* |? |
\-----------------------/</pre>
The SF, ZF, and PF flags are set according to the result; the OF, AF, and CF flags are undefined.
 
[[[01485.htm|prev]]][[[01487.htm|next]]][[[01481.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01483.htm|Description]]
 
[[01485.htm|Flags Affected]]
 
[[01484.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01486.htm|prev]]][[[01488.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== AAM-ASCII Adjust AX after Multiply ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|D4 0A    |AAM                |X|X|X|X|X|X|ASCII adjust AX after            |
\------------------------------------------------------------------------------/</pre>
 
-----
 
Run the AAM instruction only after running a MUL instruction between two unpacked BCD digits that leaves the result in the AX register. Because the result is less than 100, it is contained entirely in the AL register. The AAM instruction unpacks the AL result by dividing AL by the second byte of the opcode, leaving the quotient (most-significant digit) in the AH register and the remainder (least-significant digit) in the AL register.
 
 
-----
 
[[01489.htm|Description]]
 
[[01491.htm|Flags Affected]]
 
[[01490.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01487.htm|prev]]][[[01489.htm|next]]][[[01487.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|D4 0A    |AAM                |X|X|X|X|X|X|ASCII adjust AX after            |
\------------------------------------------------------------------------------/</pre>
[[[01488.htm|prev]]][[[01490.htm|next]]][[[01487.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Run the AAM instruction only after running a MUL instruction between two unpacked BCD digits that leaves the result in the AX register. Because the result is less than 100, it is contained entirely in the AL register. The AAM instruction unpacks the AL result by dividing AL by the second byte of the opcode, leaving the quotient (most-significant digit) in the AH register and the remainder (least-significant digit) in the AL register.
 
[[[01489.htm|prev]]][[[01491.htm|next]]][[[01487.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>regAL � AL;
AH� regAL / imm8;
AL� regAL MOD imm8;</pre>
'''Note:'''imm8 has the value of the instruction's second byte. The second byte under normally assembly of this instruction will be 0A., however, explicit modification of this byte will result in the operation described above and may alter results.
 
[[[01490.htm|prev]]][[[01492.htm|next]]][[[01487.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |* |* |? |* |? |
\-----------------------/</pre>
The SF, ZF, and PF flags are set according to the result; the OF, AF, and CF flags are undefined.
 
[[[01491.htm|prev]]][[[01493.htm|next]]][[[01487.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01489.htm|Description]]
 
[[01491.htm|Flags Affected]]
 
[[01490.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01492.htm|prev]]][[[01494.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== AAS-ASCII Adjust AL after Subtraction ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3F        |AAS                |X|X|X|X|X|X|ASCII adjust AL after subtraction |
\------------------------------------------------------------------------------/</pre>
 
-----
 
Run the AAS instruction only after a SUB instruction that leaves the byte result in the AL register. The lower nibbles of the operands of the SUB instruction must have been in the range of 0 through 9 (BCD digits). In this case, the AAS instruction adjusts the AL register so it contains the correct decimal digit result. If the subtraction produced a decimal carry, the AH register is decremented, and the CF and AF flags are set. If no decimal carry occurred, the CF and AF flags are cleared, and the AH register is unchanged. In either case, the AL register is left with its top nibble set to 0. To convert the AL result to an ASCII result, follow the AAS instruction with OR AL, 30H.
 
 
-----
 
[[01495.htm|Description]]
 
[[01497.htm|Flags Affected]]
 
[[01496.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01493.htm|prev]]][[[01495.htm|next]]][[[01493.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3F        |AAS                |X|X|X|X|X|X|ASCII adjust AL after subtraction |
\------------------------------------------------------------------------------/</pre>
[[[01494.htm|prev]]][[[01496.htm|next]]][[[01493.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Run the AAS instruction only after a SUB instruction that leaves the byte result in the AL register. The lower nibbles of the operands of the SUB instruction must have been in the range of 0 through 9 (BCD digits). In this case, the AAS instruction adjusts the AL register so it contains the correct decimal digit result. If the subtraction produced a decimal carry, the AH register is decremented, and the CF and AF flags are set. If no decimal carry occurred, the CF and AF flags are cleared, and the AH register is unchanged. In either case, the AL register is left with its top nibble set to 0. To convert the AL result to an ASCII result, follow the AAS instruction with OR AL, 30H.
 
[[[01495.htm|prev]]][[[01497.htm|next]]][[[01493.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>ALborrow � AL &lt; 6; (* 1 if true *)
IF (AL AND 0FH) &gt; 9 OR AF = 1
THEN
    AL � (AL - 6) AND 0FH;
    AH � AH - 1 - ALborrow;
    AF � 1;
    CF � 1;
ELSE
    CF � 0;
    AF � 0;
    AL � AL AND 0FH
FI;</pre>
[[[01496.htm|prev]]][[[01498.htm|next]]][[[01493.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |? |? |* |? |* |
\-----------------------/</pre>
The AF and CF flags are set if there is a decimal carry, cleared if there is no decimal carry; the OF, SF, ZF, and PF flags are undefined.
 
[[[01497.htm|prev]]][[[01499.htm|next]]][[[01493.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01495.htm|Description]]
 
[[01497.htm|Flags Affected]]
 
[[01496.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01498.htm|prev]]][[[01500.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ADC-Add with Carry ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|14 ib    |ADC AL,imm8        |X|X|X|X|X|X|Add with carry immediate byte to  |
|          |                    | | | | | | |AL                                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|15 iw    |ADC AX,imm16        |X|X|X|X|X|X|Add with carry immediate word to  |
|          |                    | | | | | | |AX                                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|15 id    |ADC EAX,imm32      | | | |X|X|X|Add with carry immediate dword to |
|          |                    | | | | | | |EAX                              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /2 ib  |ADC r/m8,imm8      |X|X|X|X|X|X|Add with carry immediate byte to  |
|          |                    | | | | | | |r/m byte                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /2 iw  |ADC r/m16,imm16    |X|X|X|X|X|X|Add with carry immediate word to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /2 id  |ADC r/m32,imm32    | | | |X|X|X|Add with carry immediate dword to |
|          |                    | | | | | | |r/m dword                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /2 ib  |ADC r/m16,imm8      |X|X|X|X|X|X|Add with carry sign-extended      |
|          |                    | | | | | | |immediate byte to r/m word        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /2 ib  |ADC r/m32,imm8      | | | |X|X|X|Add with carry sign-extended      |
|          |                    | | | | | | |immediate byte into r/m dword    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|10 /r    |ADC r/m8,r8        |X|X|X|X|X|X|Add with carry byte register to  |
|          |                    | | | | | | |r/m byte                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|11 /r    |ADC r/m16,r16      |X|X|X|X|X|X|Add with carry word register to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|11 /r    |ADC r/m32,r32      | | | |X|X|X|Add with carry dword register to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|12 /r    |ADC r8,r/m8        |X|X|X|X|X|X|Add with carry r/m byte to byte  |
|          |                    | | | | | | |register                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|13 /r    |ADC r16,r/m16      |X|X|X|X|X|X|Add with carry r/m word to word  |
|          |                    | | | | | | |register                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|13 /r    |ADC r32,r/m32      | | | |X|X|X|Add with carry r/m dword to dword |
|          |                    | | | | | | |register                          |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The ADC instruction performs an integer addition of the two operands DEST and SRC and the carry flag, CF. The result of the addition is assigned to the first operand (DEST), and the flags are set accordingly. The ADC instruction is usually run as part of a multi-byte or multi-word addition operation. When an immediate byte value is added to a word or doubleword operand, the immediate value is first sign-extended to the size of the word or doubleword operand.
 
 
-----
 
[[01501.htm|Description]]
 
[[01503.htm|Flags Affected]]
 
[[01502.htm|Operation]]
 
[[01504.htm|Protected Mode Exceptions]]
 
[[01505.htm|Real Address Mode Exceptions]]
 
[[01506.htm|Virtual 8086 Mode Exceptions]]
 
[[[01499.htm|prev]]][[[01501.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|14 ib    |ADC AL,imm8        |X|X|X|X|X|X|Add with carry immediate byte to  |
|          |                    | | | | | | |AL                                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|15 iw    |ADC AX,imm16        |X|X|X|X|X|X|Add with carry immediate word to  |
|          |                    | | | | | | |AX                                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|15 id    |ADC EAX,imm32      | | | |X|X|X|Add with carry immediate dword to |
|          |                    | | | | | | |EAX                              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /2 ib  |ADC r/m8,imm8      |X|X|X|X|X|X|Add with carry immediate byte to  |
|          |                    | | | | | | |r/m byte                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /2 iw  |ADC r/m16,imm16    |X|X|X|X|X|X|Add with carry immediate word to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /2 id  |ADC r/m32,imm32    | | | |X|X|X|Add with carry immediate dword to |
|          |                    | | | | | | |r/m dword                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /2 ib  |ADC r/m16,imm8      |X|X|X|X|X|X|Add with carry sign-extended      |
|          |                    | | | | | | |immediate byte to r/m word        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /2 ib  |ADC r/m32,imm8      | | | |X|X|X|Add with carry sign-extended      |
|          |                    | | | | | | |immediate byte into r/m dword    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|10 /r    |ADC r/m8,r8        |X|X|X|X|X|X|Add with carry byte register to  |
|          |                    | | | | | | |r/m byte                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|11 /r    |ADC r/m16,r16      |X|X|X|X|X|X|Add with carry word register to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|11 /r    |ADC r/m32,r32      | | | |X|X|X|Add with carry dword register to  |
|          |                    | | | | | | |r/m word                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|12 /r    |ADC r8,r/m8        |X|X|X|X|X|X|Add with carry r/m byte to byte  |
|          |                    | | | | | | |register                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|13 /r    |ADC r16,r/m16      |X|X|X|X|X|X|Add with carry r/m word to word  |
|          |                    | | | | | | |register                          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|13 /r    |ADC r32,r/m32      | | | |X|X|X|Add with carry r/m dword to dword |
|          |                    | | | | | | |register                          |
\------------------------------------------------------------------------------/</pre>
[[[01500.htm|prev]]][[[01502.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The ADC instruction performs an integer addition of the two operands DEST and SRC and the carry flag, CF. The result of the addition is assigned to the first operand (DEST), and the flags are set accordingly. The ADC instruction is usually run as part of a multi-byte or multi-word addition operation. When an immediate byte value is added to a word or doubleword operand, the immediate value is first sign-extended to the size of the word or doubleword operand.
 
[[[01501.htm|prev]]][[[01503.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>DEST � DEST + SRC + CF;</pre>
[[[01502.htm|prev]]][[[01504.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|* |  |  |* |* |* |* |* |
\-----------------------/</pre>
The OF, SF, ZF, AF, CF, and PF flags are set according to the result.
 
[[[01503.htm|prev]]][[[01505.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01504.htm|prev]]][[[01506.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01505.htm|prev]]][[[01507.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01506.htm|prev]]][[[01508.htm|next]]][[[01499.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01501.htm|Description]]
 
[[01503.htm|Flags Affected]]
 
[[01502.htm|Operation]]
 
[[01504.htm|Protected Mode Exceptions]]
 
[[01505.htm|Real Address Mode Exceptions]]
 
[[01506.htm|Virtual 8086 Mode Exceptions]]
 
[[[01507.htm|prev]]][[[01509.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ADD-Add ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|04 ib    |ADD AL,imm8        |X|X|X|X|X|X|Add immediate byte to AL          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|05 iw    |ADD AX,imm16        |X|X|X|X|X|X|Add immediate word to AX          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|05 id    |ADD EAX,imm32      | | | |X|X|X|Add immediate dword to EAX        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /0 ib  |ADD r/m8,imm8      |X|X|X|X|X|X|Add immediate byte to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /0 iw  |ADD r/m16,imm16    |X|X|X|X|X|X|Add immediate word to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /0 id  |ADD r/m32,imm32    | | | |X|X|X|Add immediate dword to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /0 ib  |ADD r/m16,imm8      |X|X|X|X|X|X|Add sign-extended immediate byte  |
|          |                    | | | | | | |to r/m word                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /0 ib  |ADD r/m32,imm8      | | | |X|X|X|Add sign-extended immediate byte  |
|          |                    | | | | | | |to r/m dword                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|00 /r    |ADD r/m8,r8        |X|X|X|X|X|X|Add byte register to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|01 /r    |ADD r/m16,r16      |X|X|X|X|X|X|Add word register to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|01 /r    |ADD r/m32,r32      | | | |X|X|X|Add dword register to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|02 /r    |ADD r8,r/m8        |X|X|X|X|X|X|Add r/m byte to byte register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|03 /r    |ADD r16,r/m16      |X|X|X|X|X|X|Add r/m word to word register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|03 /r    |ADD r32,r/m32      | | | |X|X|X|Add r/m dword to dword register  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The ADD instruction performs an integer addition of the two operands (DEST and SRC). The result of the addition is assigned to the first operand (DEST ), and the flags are set accordingly.
 
When an immediate byte is added to a word or doubleword operand, the immediate value is sign-extended to the size of the word or doubleword operand.
 
 
-----
 
[[01510.htm|Description]]
 
[[01512.htm|Flags Affected]]
 
[[01511.htm|Operation]]
 
[[01513.htm|Protected Mode Exceptions]]
 
[[01514.htm|Real Address Mode Exceptions]]
 
[[01515.htm|Virtual 8086 Mode Exceptions]]
 
[[[01508.htm|prev]]][[[01510.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|04 ib    |ADD AL,imm8        |X|X|X|X|X|X|Add immediate byte to AL          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|05 iw    |ADD AX,imm16        |X|X|X|X|X|X|Add immediate word to AX          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|05 id    |ADD EAX,imm32      | | | |X|X|X|Add immediate dword to EAX        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /0 ib  |ADD r/m8,imm8      |X|X|X|X|X|X|Add immediate byte to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /0 iw  |ADD r/m16,imm16    |X|X|X|X|X|X|Add immediate word to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /0 id  |ADD r/m32,imm32    | | | |X|X|X|Add immediate dword to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /0 ib  |ADD r/m16,imm8      |X|X|X|X|X|X|Add sign-extended immediate byte  |
|          |                    | | | | | | |to r/m word                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /0 ib  |ADD r/m32,imm8      | | | |X|X|X|Add sign-extended immediate byte  |
|          |                    | | | | | | |to r/m dword                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|00 /r    |ADD r/m8,r8        |X|X|X|X|X|X|Add byte register to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|01 /r    |ADD r/m16,r16      |X|X|X|X|X|X|Add word register to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|01 /r    |ADD r/m32,r32      | | | |X|X|X|Add dword register to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|02 /r    |ADD r8,r/m8        |X|X|X|X|X|X|Add r/m byte to byte register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|03 /r    |ADD r16,r/m16      |X|X|X|X|X|X|Add r/m word to word register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|03 /r    |ADD r32,r/m32      | | | |X|X|X|Add r/m dword to dword register  |
\------------------------------------------------------------------------------/</pre>
[[[01509.htm|prev]]][[[01511.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The ADD instruction performs an integer addition of the two operands (DEST and SRC). The result of the addition is assigned to the first operand (DEST ), and the flags are set accordingly.
 
When an immediate byte is added to a word or doubleword operand, the immediate value is sign-extended to the size of the word or doubleword operand.
 
[[[01510.htm|prev]]][[[01512.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>DEST � DEST + SRC;</pre>
[[[01511.htm|prev]]][[[01513.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|* |  |  |* |* |* |* |* |
\-----------------------/</pre>
The OF, SF, ZF, AF, CF, and PF flags are set according to the result.
 
[[[01512.htm|prev]]][[[01514.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) is the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01513.htm|prev]]][[[01515.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01514.htm|prev]]][[[01516.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01515.htm|prev]]][[[01517.htm|next]]][[[01508.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01510.htm|Description]]
 
[[01512.htm|Flags Affected]]
 
[[01511.htm|Operation]]
 
[[01513.htm|Protected Mode Exceptions]]
 
[[01514.htm|Real Address Mode Exceptions]]
 
[[01515.htm|Virtual 8086 Mode Exceptions]]
 
[[[01516.htm|prev]]][[[01518.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== AND-Logical AND ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|24 ib    |AND AL,imm8        |X|X|X|X|X|X|AND immediate byte to AL          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|25 iw    |AND AX,imm16        |X|X|X|X|X|X|AND immediate word to AX          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|25 id    |AND EAX,imm32      | | | |X|X|X|AND immediate dword to EAX        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /r ib  |AND r/m8,imm8      |X|X|X|X|X|X|AND immediate byte to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /4 iw  |AND r/m16,imm16    |X|X|X|X|X|X|AND immediate word to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /r id  |AND r/m32,imm32    | | | |X|X|X|AND immediate dword to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /4 ib  |AND r/m16,imm8      | | | |X|X|X|AND sign-extended immediate byte  |
|          |                    | | | | | | |to r/m word                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /4 ib  |AND r/m32,imm8      | | | |X|X|X|AND sign-extended immediate byte  |
|          |                    | | | | | | |with r/m dword                    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|20 /r    |AND r/m8,r8        |X|X|X|X|X|X|AND byte register to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|21 /r    |AND r/m16,r16      |X|X|X|X|X|X|AND word register to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|21 /r    |AND r/m32,r32      | | | |X|X|X|AND dword register to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|22 /r    |AND r8,r/m8        |X|X|X|X|X|X|AND r/m byte to byte register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|23 /r    |AND r16,r/m16      |X|X|X|X|X|X|AND r/m word to word register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|23 /r    |AND r32,r/m32      | | | |X|X|X|AND r/m dword to dword register  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
Each bit of the result of the AND instruction is a 1 if both corresponding bits of the operands are 1; otherwise, it becomes a 0.
 
 
-----
 
[[01519.htm|Description]]
 
[[01521.htm|Flags Affected]]
 
[[01520.htm|Operation]]
 
[[01522.htm|Protected Mode Exceptions]]
 
[[01523.htm|Real Address Mode Exceptions]]
 
[[01524.htm|Virtual 8086 Mode Exceptions]]
 
[[[01517.htm|prev]]][[[01519.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|24 ib    |AND AL,imm8        |X|X|X|X|X|X|AND immediate byte to AL          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|25 iw    |AND AX,imm16        |X|X|X|X|X|X|AND immediate word to AX          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|25 id    |AND EAX,imm32      | | | |X|X|X|AND immediate dword to EAX        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /r ib  |AND r/m8,imm8      |X|X|X|X|X|X|AND immediate byte to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /4 iw  |AND r/m16,imm16    |X|X|X|X|X|X|AND immediate word to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /r id  |AND r/m32,imm32    | | | |X|X|X|AND immediate dword to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /4 ib  |AND r/m16,imm8      | | | |X|X|X|AND sign-extended immediate byte  |
|          |                    | | | | | | |to r/m word                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /4 ib  |AND r/m32,imm8      | | | |X|X|X|AND sign-extended immediate byte  |
|          |                    | | | | | | |with r/m dword                    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|20 /r    |AND r/m8,r8        |X|X|X|X|X|X|AND byte register to r/m byte    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|21 /r    |AND r/m16,r16      |X|X|X|X|X|X|AND word register to r/m word    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|21 /r    |AND r/m32,r32      | | | |X|X|X|AND dword register to r/m dword  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|22 /r    |AND r8,r/m8        |X|X|X|X|X|X|AND r/m byte to byte register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|23 /r    |AND r16,r/m16      |X|X|X|X|X|X|AND r/m word to word register    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|23 /r    |AND r32,r/m32      | | | |X|X|X|AND r/m dword to dword register  |
\------------------------------------------------------------------------------/</pre>
[[[01518.htm|prev]]][[[01520.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
Each bit of the result of the AND instruction is a 1 if both corresponding bits of the operands are 1; otherwise, it becomes a 0.
 
[[[01519.htm|prev]]][[[01521.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>DEST � DEST AND SRC;
CF � 0;
OF � 0;</pre>
[[[01520.htm|prev]]][[[01522.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|0 |  |  |* |* |? |* |0 |
\-----------------------/</pre>
The CF and OF flags are cleared; the PF, SF, and ZF flags are set according to the result; the AF flag is undefined.
 
[[[01521.htm|prev]]][[[01523.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01522.htm|prev]]][[[01524.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01523.htm|prev]]][[[01525.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01524.htm|prev]]][[[01526.htm|next]]][[[01517.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01519.htm|Description]]
 
[[01521.htm|Flags Affected]]
 
[[01520.htm|Operation]]
 
[[01522.htm|Protected Mode Exceptions]]
 
[[01523.htm|Real Address Mode Exceptions]]
 
[[01524.htm|Virtual 8086 Mode Exceptions]]
 
[[[01525.htm|prev]]][[[01527.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== ARPL-Adjust RPL Field of Selector ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|63 /r    |ARPL r/m16,r16      | | |X|X|X|X|Adjust RPL of r/m16 to not less  |
|          |                    | | | | | | |than RPL of r16                  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The ARPL instruction has two operands. The first operand is a 16-bit memory variable or word register that contains the value of a selector. The second operand is a word register. If the RPL field (&quot;requested privilege level&quot;- bottom two bits) of the first operand is less than the RPL field of the second operand, the ZF flag is set and the RPL field of the first operand is increased to match the second operand. Otherwise, the ZF flag is cleared and no change is made to the first operand.
 
The ARPL instruction appears in operating system software, not in application programs. It is used to guarantee that a selector parameter to a subroutine does not request more privilege than the caller is allowed. The second operand of the ARPL instruction is normally a register that contains the CS selector value of the caller.
 
 
-----
 
[[01528.htm|Description]]
 
[[01530.htm|Flags Affected]]
 
[[01529.htm|Operation]]
 
[[01531.htm|Protected Mode Exceptions]]
 
[[01532.htm|Real Address Mode Exceptions]]
 
[[01533.htm|Virtual 8086 Mode Exceptions]]
 
[[[01526.htm|prev]]][[[01528.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|63 /r    |ARPL r/m16,r16      | | |X|X|X|X|Adjust RPL of r/m16 to not less  |
|          |                    | | | | | | |than RPL of r16                  |
\------------------------------------------------------------------------------/</pre>
[[[01527.htm|prev]]][[[01529.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The ARPL instruction has two operands. The first operand is a 16-bit memory variable or word register that contains the value of a selector. The second operand is a word register. If the RPL field (&quot;requested privilege level&quot;- bottom two bits) of the first operand is less than the RPL field of the second operand, the ZF flag is set and the RPL field of the first operand is increased to match the second operand. Otherwise, the ZF flag is cleared and no change is made to the first operand.
 
The ARPL instruction appears in operating system software, not in application programs. It is used to guarantee that a selector parameter to a subroutine does not request more privilege than the caller is allowed. The second operand of the ARPL instruction is normally a register that contains the CS selector value of the caller.
 
[[[01528.htm|prev]]][[[01530.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF RBL bits(0,1) of DEST &lt; RPL bits(0,1) of SRC
THEN
    ZF � 1;
    RPL bits(0,1) of DEST � RPL bits (0,1) of SRC;
ELSE
    ZF � 0;
FI;</pre>
[[[01529.htm|prev]]][[[01531.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |* |  |  |  |
\-----------------------/</pre>
The ZF flag is set if the RPL field of the first operand is less than that of the second operand, otherwise ZF is cleared.
 
[[[01530.htm|prev]]][[[01532.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01531.htm|prev]]][[[01533.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 6; the ARPL instruction is not recognized in Real Address Mode.
 
[[[01532.htm|prev]]][[[01534.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Interrupt 6; the ARPL instruction is not recognized in Virtual 8086 Mode.
 
[[[01533.htm|prev]]][[[01535.htm|next]]][[[01526.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01528.htm|Description]]
 
[[01530.htm|Flags Affected]]
 
[[01529.htm|Operation]]
 
[[01531.htm|Protected Mode Exceptions]]
 
[[01532.htm|Real Address Mode Exceptions]]
 
[[01533.htm|Virtual 8086 Mode Exceptions]]
 
[[[01534.htm|prev]]][[[01536.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BOUND-Check Array Index Against Bounds ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|62 /r    |BOUND r16,m16&amp;16    | |X|X|X|X|X|Check if r16 is within m16&amp;16    |
|          |                    | | | | | | |bounds (passes test)              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|62 /r    |BOUND r32,m32&amp;32    | | | |X|X|X|Check if r32 is within m32&amp;32    |
|          |                    | | | | | | |bounds (passes test)              |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BOUND instruction ensures that a signed array index is within the limits specified by a block of memory consisting of an upper and a lower bound. Each bound uses one word when the operand-size attribute is 16-bits and a doubleword when the operand-size attribute is 32-bits. The first operand (a register) must be greater than or equal to the first bound in memory (lower bound), and less than or equal to the second bound in memory (upper bound) plus the number of bytes occupied for the operand size. If the register is not within bounds, an Interrupt 5 occurs; the return EIP points to the BOUND instruction.
 
The bounds limit data structure is usually placed just before the array itself, making the limits addressable via a constant offset from the beginning of the array.
 
 
-----
 
[[01537.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01538.htm|Operation]]
 
[[01539.htm|Protected Mode Exceptions]]
 
[[01540.htm|Real Address Mode Exceptions]]
 
[[01541.htm|Virtual 8086 Mode Exceptions]]
 
[[[01535.htm|prev]]][[[01537.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|62 /r    |BOUND r16,m16&amp;16    | |X|X|X|X|X|Check if r16 is within m16&amp;16    |
|          |                    | | | | | | |bounds (passes test)              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|62 /r    |BOUND r32,m32&amp;32    | | | |X|X|X|Check if r32 is within m32&amp;32    |
|          |                    | | | | | | |bounds (passes test)              |
\------------------------------------------------------------------------------/</pre>
[[[01536.htm|prev]]][[[01538.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BOUND instruction ensures that a signed array index is within the limits specified by a block of memory consisting of an upper and a lower bound. Each bound uses one word when the operand-size attribute is 16-bits and a doubleword when the operand-size attribute is 32-bits. The first operand (a register) must be greater than or equal to the first bound in memory (lower bound), and less than or equal to the second bound in memory (upper bound) plus the number of bytes occupied for the operand size. If the register is not within bounds, an Interrupt 5 occurs; the return EIP points to the BOUND instruction.
 
The bounds limit data structure is usually placed just before the array itself, making the limits addressable via a constant offset from the beginning of the array.
 
[[[01537.htm|prev]]][[[01539.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF (LeftSRC &lt; [RightSRC] OR LeftSRC &gt; [RightSRC +
OperandSize/8])
  (* Under lower bound or over upper bound *)
THEN Interrupt 5;
FI;</pre>
[[[01538.htm|prev]]][[[01540.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
Interrupt 5 if the bounds test fails, as described above; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
The second operand must be a memory operand, not a register. If the BOUND instruction is run with a ModR/M byte representing a register as the second operand, #UD occurs.
 
[[[01539.htm|prev]]][[[01541.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 5 if the bounds test fails; Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH; Interrupt 6 if the second operand is a register.
 
[[[01540.htm|prev]]][[[01542.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01541.htm|prev]]][[[01543.htm|next]]][[[01535.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01537.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01538.htm|Operation]]
 
[[01539.htm|Protected Mode Exceptions]]
 
[[01540.htm|Real Address Mode Exceptions]]
 
[[01541.htm|Virtual 8086 Mode Exceptions]]
 
[[[01542.htm|prev]]][[[01544.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BSF-Bit Scan Forward ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BC    |BSF r16,r/m16      | | | |X|X|X|Bit scan forward on r/m word      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BC    |BSF r32,r/m32      | | | |X|X|X|Bit scan forward on r/m dword    |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BSF instruction scans the bits in the second word or doubleword operand starting with bit 0. The ZF flag is set if all the bits are 0; otherwise, the ZF flag is cleared and the destination register is loaded with the bit index of the first set bit.
 
 
-----
 
[[01545.htm|Description]]
 
[[01547.htm|Flags Affected]]
 
[[01546.htm|Operation]]
 
[[01548.htm|Protected Mode Exceptions]]
 
[[01549.htm|Real Address Mode Exceptions]]
 
[[01550.htm|Virtual 8086 Mode Exceptions]]
 
[[[01543.htm|prev]]][[[01545.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BC    |BSF r16,r/m16      | | | |X|X|X|Bit scan forward on r/m word      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BC    |BSF r32,r/m32      | | | |X|X|X|Bit scan forward on r/m dword    |
\------------------------------------------------------------------------------/</pre>
[[[01544.htm|prev]]][[[01546.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BSF instruction scans the bits in the second word or doubleword operand starting with bit 0. The ZF flag is set if all the bits are 0; otherwise, the ZF flag is cleared and the destination register is loaded with the bit index of the first set bit.
 
[[[01545.htm|prev]]][[[01547.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF r/m = 0
THEN
    ZF � 1;
    register � UNDEFINED;
ELSE
    temp � 0;
    ZF � 0;
    WHILE BIT[r/m,temp] = 0
    DO
      temp � temp + 1;
      register � temp;
  OD;
FI;</pre>
[[[01546.htm|prev]]][[[01548.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |? |* |? |? |? |
\-----------------------/</pre>
The ZF flag is set if all bits are 0; otherwise, the ZF flag is cleared. OF , SF, AF, PF, CF = undefined.
 
[[[01547.htm|prev]]][[[01549.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF( fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01548.htm|prev]]][[[01550.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01549.htm|prev]]][[[01551.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01550.htm|prev]]][[[01552.htm|next]]][[[01543.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01545.htm|Description]]
 
[[01547.htm|Flags Affected]]
 
[[01546.htm|Operation]]
 
[[01548.htm|Protected Mode Exceptions]]
 
[[01549.htm|Real Address Mode Exceptions]]
 
[[01550.htm|Virtual 8086 Mode Exceptions]]
 
[[[01551.htm|prev]]][[[01553.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BSR-Bit Scan Reverse ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BD    |BSR r16,r/m16      | | | |X|X|X|Bit scan reverse on r/m word      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BD    |BSR r32,r/m32      | | | |X|X|X|Bit scan reverse on r/m dword    |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BSR instruction scans the bits in the second word or doubleword operand from the most significant bit to the least significant bit. The ZF flag is set if all the bits are 0; otherwise, the ZF flag is cleared and the destination register is loaded with the bit index of the first set bit found when scanning in the reverse direction.
 
 
-----
 
[[01554.htm|Description]]
 
[[01556.htm|Flags Affected]]
 
[[01555.htm|Operation]]
 
[[01557.htm|Protected Mode Exceptions]]
 
[[01558.htm|Real Address Mode Exceptions]]
 
[[01559.htm|Virtual 8086 Mode Exceptions]]
 
[[[01552.htm|prev]]][[[01554.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BD    |BSR r16,r/m16      | | | |X|X|X|Bit scan reverse on r/m word      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BD    |BSR r32,r/m32      | | | |X|X|X|Bit scan reverse on r/m dword    |
\------------------------------------------------------------------------------/</pre>
[[[01553.htm|prev]]][[[01555.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BSR instruction scans the bits in the second word or doubleword operand from the most significant bit to the least significant bit. The ZF flag is set if all the bits are 0; otherwise, the ZF flag is cleared and the destination register is loaded with the bit index of the first set bit found when scanning in the reverse direction.
 
[[[01554.htm|prev]]][[[01556.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF r/m = 0
THEN
    ZF � 1;
    register � UNDEFINED;
ELSE
    temp � OperandSize =1;
    ZF � 0;
    WHILE BIT[r/m,temp] = 0
    DO
      temp � temp - 1;
      register � temp;
  OD;
FI;</pre>
[[[01555.htm|prev]]][[[01557.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|? |  |  |? |* |? |? |? |
\-----------------------/</pre>
The ZF flag is set if all bits are 0; otherwise, the ZF flag is cleared. OS , SF, AF, PF, CF = undefined.
 
[[[01556.htm|prev]]][[[01558.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01557.htm|prev]]][[[01559.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01558.htm|prev]]][[[01560.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01559.htm|prev]]][[[01561.htm|next]]][[[01552.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01554.htm|Description]]
 
[[01556.htm|Flags Affected]]
 
[[01555.htm|Operation]]
 
[[01557.htm|Protected Mode Exceptions]]
 
[[01558.htm|Real Address Mode Exceptions]]
 
[[01559.htm|Virtual 8086 Mode Exceptions]]
 
[[[01560.htm|prev]]][[[01562.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BSWAP-Byte Swap ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F C8+rd  |BSWAP r32          | | | | |X|X|Swap bytes to convert little/big  |
|          |                    | | | | | | |endian data in a 32-bit register  |
|          |                    | | | | | | |to big/little endian form        |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BSWAP instruction reverses the byte order of a 32-bit register, converting a value in little/big endian form to big/little endian form. When BSWAP is used with 16-bit operand size, the result left in the destination register is undefined.
 
 
-----
 
[[01563.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01565.htm|Notes]]
 
[[01564.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01561.htm|prev]]][[[01563.htm|next]]][[[01561.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F C8+rd  |BSWAP r32          | | | | |X|X|Swap bytes to convert little/big  |
|          |                    | | | | | | |endian data in a 32-bit register  |
|          |                    | | | | | | |to big/little endian form        |
\------------------------------------------------------------------------------/</pre>
[[[01562.htm|prev]]][[[01564.htm|next]]][[[01561.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BSWAP instruction reverses the byte order of a 32-bit register, converting a value in little/big endian form to big/little endian form. When BSWAP is used with 16-bit operand size, the result left in the destination register is undefined.
 
[[[01563.htm|prev]]][[[01565.htm|next]]][[[01561.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>TEMP � r32
r32(7..0) � TEMP(31..24)
r32(15..8) � TEMP(23..16)
r32(23..16) � TEMP(15..8)
r32(31..24) � TEMP(7.0)</pre>
[[[01564.htm|prev]]][[[01566.htm|next]]][[[01561.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
BSWAP is not supported on Intel386 processors. Include functionally- equivalent code for Intel386 CPUs.
 
[[[01565.htm|prev]]][[[01567.htm|next]]][[[01561.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01563.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01565.htm|Notes]]
 
[[01564.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01566.htm|prev]]][[[01568.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BT-Bit Test ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F A3    |BT r/m16,r16        | | | |X|X|X|Save bit in carry flag            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F A3    |BT r/m32,r32        | | | |X|X|X|Save bit in carry flag            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /4  |BT r/m16,imm8      | | | |X|X|X|Save bit in carry flag            |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /4  |BT r/m32,imm8      | | | |X|X|X|Save bit in carry flag            |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BT instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag.
 
 
-----
 
[[01569.htm|Description]]
 
[[01571.htm|Flags Affected]]
 
[[01575.htm|Notes]]
 
[[01570.htm|Operation]]
 
[[01572.htm|Protected Mode Exceptions]]
 
[[01573.htm|Real Address Mode Exceptions]]
 
[[01574.htm|Virtual 8086 Mode Exceptions]]
 
[[[01567.htm|prev]]][[[01569.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F A3    |BT r/m16,r16        | | | |X|X|X|Save bit in carry flag            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F A3    |BT r/m32,r32        | | | |X|X|X|Save bit in carry flag            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /4  |BT r/m16,imm8      | | | |X|X|X|Save bit in carry flag            |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /4  |BT r/m32,imm8      | | | |X|X|X|Save bit in carry flag            |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
[[[01568.htm|prev]]][[[01570.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BT instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag.
 
[[[01569.htm|prev]]][[[01571.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � BIT [LeftSRC, RightSRC];</pre>
[[[01570.htm|prev]]][[[01572.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |* |
\-----------------------/</pre>
The CF flag contains the value of the selected bit.
 
[[[01571.htm|prev]]][[[01573.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF( fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01572.htm|prev]]][[[01574.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01573.htm|prev]]][[[01575.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01574.htm|prev]]][[[01576.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
The index of the selected bit can be given by the immediate constant in the instruction or by a value in a general register. Only an 8-bit immediate value is used in the instruction. This operand is taken modulo 32, so the range of immediate bit offsets is 0..31. This allows any bit within a register to be selected. For memory bit strings, this immediate field gives only the bit offset within a word or doubleword.
 
Immediate bit offsets larger than 31 are supported by some assemblers by using the immediate bit offset field in combination with the displacement field of the memory operand. In this case, the low-order 3 to 5 bits (3 for 16 bit operands, 5 for 32-bit operands) of the immediate bit offset are stored in the immediate bit offset field, and the high-order bits are shifted and combined with the byte displacement in the addressing mode by the assembler. The processor will ignore the high-order bits if they are not zero.
 
When accessing a bit in memory, the processor may access four bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (4* (BitOffset DIV 32))</pre>
for a 32-bit operand size, or two bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (2 * (BitOffset DIV 16))</pre>
for a 16-bit operand size. It may do so even when only a single byte needs to be accessed in order to reach the given bit. You must therefore avoid referencing areas of memory close to address space holes. In particular, avoid references to memory-mapped I/O registers. Instead, use the MOV instructions to load from or store to these addresses, and use the register form of these instructions to manipulate the data.
 
[[[01575.htm|prev]]][[[01577.htm|next]]][[[01567.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01569.htm|Description]]
 
[[01571.htm|Flags Affected]]
 
[[01575.htm|Notes]]
 
[[01570.htm|Operation]]
 
[[01572.htm|Protected Mode Exceptions]]
 
[[01573.htm|Real Address Mode Exceptions]]
 
[[01574.htm|Virtual 8086 Mode Exceptions]]
 
[[[01576.htm|prev]]][[[01578.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BTC-Bit Test and Complement ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BB    |BTC r/m16,r16      | | | |X|X|X|Save bit in carry flag and        |
|          |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BB    |BTC r/m32,r32      | | | |X|X|X|Save bit in carry flag and        |
|          |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /7  |BTC r/m16,imm8      | | | |X|X|X|Save bit in carry flag and        |
|ib        |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /7  |BTC r/m32,imm8      | | | |X|X|X|Save bit in carry flag and        |
|ib        |                    | | | | | | |complement                        |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BTC instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then complements the bit.
 
 
-----
 
[[01579.htm|Description]]
 
[[01581.htm|Flags Affected]]
 
[[01585.htm|Notes]]
 
[[01580.htm|Operation]]
 
[[01582.htm|Protected Mode Exceptions]]
 
[[01583.htm|Real Address Mode Exceptions]]
 
[[01584.htm|Virtual 8086 Mode Exceptions]]
 
[[[01577.htm|prev]]][[[01579.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BB    |BTC r/m16,r16      | | | |X|X|X|Save bit in carry flag and        |
|          |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BB    |BTC r/m32,r32      | | | |X|X|X|Save bit in carry flag and        |
|          |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /7  |BTC r/m16,imm8      | | | |X|X|X|Save bit in carry flag and        |
|ib        |                    | | | | | | |complement                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /7  |BTC r/m32,imm8      | | | |X|X|X|Save bit in carry flag and        |
|ib        |                    | | | | | | |complement                        |
\------------------------------------------------------------------------------/</pre>
[[[01578.htm|prev]]][[[01580.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BTC instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then complements the bit.
 
[[[01579.htm|prev]]][[[01581.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � BIT[LeftSRC, RightSRC];
BIT[LeftSRC, RightSRC] � NOT BIT[LeftSrc, RightSRC];</pre>
[[[01580.htm|prev]]][[[01582.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |* |
\-----------------------/</pre>
The CF flag contains the complement of the selected bit.
 
[[[01581.htm|prev]]][[[01583.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, and GS segments; # SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01582.htm|prev]]][[[01584.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01583.htm|prev]]][[[01585.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01584.htm|prev]]][[[01586.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
The index of the selected bit can be given by the immediate constant in the instruction or by a value in a general register. Only an 8-bit immediate value may be used in the instruction. This operand is taken modulo 32, so the range of immediate bit offsets is 0..31. This allows any bit within a register to be selected. For memory bit strings, this immediate field gives only the bit offset within a word or doubleword.
 
Immediate bit offsets larger then 31 are supported by some assemblers by using the immediate bit offset field in combination with the displacement field of the memory operand. In this case, the low-order 3 to 5 bits (3 for 16-bit operands, 5 for 32-bit operands) of the immediate bit offset are stored in the immediate bit offset field, and the high-order bits are shifted and combined with the byte displacement in the addressing mode by the assembler. The processor will ignore the high order bits if they are not zero.
 
When accessing a bit in memory, the processor may access four bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (4 * (BitOffset DIV 32))</pre>
for a 32-bit operand size, or two bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (2 * (BitOffset DIV 16))</pre>
for a 16-bit operand size. It may do so even when only a single byte needs to be accessed in order to reach the given bit. Therefore, referencing areas of memory close to address space holes should be avoided. In particular, avoid references to memory-mapped I/O registers. Instead, use the MOV instructions to load from or store to these addresses, and use the register form of these instructions to manipulate the data.
 
[[[01585.htm|prev]]][[[01587.htm|next]]][[[01577.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01579.htm|Description]]
 
[[01581.htm|Flags Affected]]
 
[[01585.htm|Notes]]
 
[[01580.htm|Operation]]
 
[[01582.htm|Protected Mode Exceptions]]
 
[[01583.htm|Real Address Mode Exceptions]]
 
[[01584.htm|Virtual 8086 Mode Exceptions]]
 
[[[01586.htm|prev]]][[[01588.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BTR-Bit Test and Reset ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F B3    |BTR r/m16,r16      | | | |X|X|X|Save bit in carry flag and reset  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F B3    |BTR r/m32,r32      | | | |X|X|X|Save bit in carry flag and reset  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /6  |BTR r/m16,imm8      | | | |X|X|X|Save bit in carry flag and reset  |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /6  |BTR r/m32,imm8      | | | |X|X|X|Save bit in carry flag and reset  |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BTR instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then stores 0 in the bit.
 
 
-----
 
[[01589.htm|Description]]
 
[[01591.htm|Flags Affected]]
 
[[01595.htm|Notes]]
 
[[01590.htm|Operation]]
 
[[01592.htm|Protected Mode Exceptions]]
 
[[01593.htm|Real Address Mode Exceptions]]
 
[[01594.htm|Virtual 8086 Mode Exceptions]]
 
[[[01587.htm|prev]]][[[01589.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F B3    |BTR r/m16,r16      | | | |X|X|X|Save bit in carry flag and reset  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F B3    |BTR r/m32,r32      | | | |X|X|X|Save bit in carry flag and reset  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /6  |BTR r/m16,imm8      | | | |X|X|X|Save bit in carry flag and reset  |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /6  |BTR r/m32,imm8      | | | |X|X|X|Save bit in carry flag and reset  |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
[[[01588.htm|prev]]][[[01590.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BTR instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then stores 0 in the bit.
 
[[[01589.htm|prev]]][[[01591.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � BIT[LeftSRC, RightSRC];
BIT[LeftSRC, RightSRC] � 0;</pre>
[[[01590.htm|prev]]][[[01592.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |* |
\-----------------------/</pre>
The CF flag contains the value of the selected bit.
 
[[[01591.htm|prev]]][[[01593.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01592.htm|prev]]][[[01594.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01593.htm|prev]]][[[01595.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01594.htm|prev]]][[[01596.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
The index of the selected bit can be given by the immediate constant in the instruction or by a value in a general register. Only an 8-bit immediate value is used in the instruction. This operand is taken modulo 32, so the range of immediate bit offsets is 0..31. This allows any bit within a register to be selected. For memory bit strings, this immediate field gives only the bit offset within a word or doubleword.
 
Immediate bit offsets larger than 31 are supported by some assemblers by using the immediate bit offset field in combination with the displacement field of the memory operand. In this case, the low-order 3 to 5-bits (3 for 16-bit operands, 5 for 32-bit operands) of the immediate bit offset are stored in the immediate bit offset field, and the high-order bits are shifted and combined with the byte displacement in the addressing mode by the assembler. The processor will ignore the high-order bits if they are not zero.
 
When accessing a bit in memory, the processor may access four bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + 4 * (BitOffset DIV 32)</pre>
for a 32-bit operand size, or two bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + 2 * (BitOffset DIV 16)</pre>
for a 16-bit operand size. It may do so even when only a single byte needs to be accessed in order to reach the given bit. You must therefore avoid referencing areas of memory close to address space holes. In particular, avoid references to memory-mapped I/O registers. Instead, use the MOV instructions to load from or store to these addresses, and use the register form of these instructions to manipulate the data.
 
[[[01595.htm|prev]]][[[01597.htm|next]]][[[01587.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01589.htm|Description]]
 
[[01591.htm|Flags Affected]]
 
[[01595.htm|Notes]]
 
[[01590.htm|Operation]]
 
[[01592.htm|Protected Mode Exceptions]]
 
[[01593.htm|Real Address Mode Exceptions]]
 
[[01594.htm|Virtual 8086 Mode Exceptions]]
 
[[[01596.htm|prev]]][[[01598.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== BTS-Bit Test and Set ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F AB    |BTS r/m16,r16      | | | |X|X|X|Save bit in carry flag and set    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F AB    |BTS r/m32,r32      | | | |X|X|X|Save bit in carry flag and set    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /5  |BTS r/m16,imm8      | | | |X|X|X|Save bit in carry flag and set    |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /5  |BTS r/m32,imm8      | | | |X|X|X|Save bit in carry flag and set    |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The BTS instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then stores 1 in the bit.
 
 
-----
 
[[01599.htm|Description]]
 
[[01601.htm|Flags Affected]]
 
[[01605.htm|Notes]]
 
[[01600.htm|Operation]]
 
[[01602.htm|Protected Mode Exceptions]]
 
[[01603.htm|Real Address Mode Exceptions]]
 
[[01604.htm|Virtual 8086 Mode Exceptions]]
 
[[[01597.htm|prev]]][[[01599.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F AB    |BTS r/m16,r16      | | | |X|X|X|Save bit in carry flag and set    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F AB    |BTS r/m32,r32      | | | |X|X|X|Save bit in carry flag and set    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /5  |BTS r/m16,imm8      | | | |X|X|X|Save bit in carry flag and set    |
|ib        |                    | | | | | | |                                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F BA /5  |BTS r/m32,imm8      | | | |X|X|X|Save bit in carry flag and set    |
|ib        |                    | | | | | | |                                  |
\------------------------------------------------------------------------------/</pre>
[[[01598.htm|prev]]][[[01600.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The BTS instruction saves the value of the bit indicated by the base (first operand) and the bit offset (second operand) into the CF flag and then stores 1 in the bit.
 
[[[01599.htm|prev]]][[[01601.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � BIT[LeftSRC, RightSRC];
BIT[LeftSRC, RightSRC] � 1;</pre>
[[[01600.htm|prev]]][[[01602.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |* |
\-----------------------/</pre>
The CF flag contains the value of the selected bit.
 
[[[01601.htm|prev]]][[[01603.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS (0) for an illegal address in the SS segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01602.htm|prev]]][[[01604.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01603.htm|prev]]][[[01605.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01604.htm|prev]]][[[01606.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
The index of the selected bit can be given by the immediate constant in the instruction or by a value in a general register. Only an 8-bit immediate value is used in the instruction. This operand is taken modulo 32, so the range of immediate bit offsets is 0..31. This allows any bit within a register to be selected. For memory bit strings, this immediate field gives only the bit offset within a word or doubleword.
 
Immediate bit offsets larger than 31 are supported by some assemblers by using the immediate bit offset field in combination with the displacement field of the memory operand. In this case, the low-order 3 to 5 bits (3 for 16-bit operands, 5 for 32-bit operands) of the immediate bit offset are stored in the immediate bit offset field, and the high-order bits are shifted and combined with the byte displacement in the addressing mode by the assembler. The processor will ignore the high-order bits if they are not zero.
 
When accessing a bit in memory, the processor may access four bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (4 * (BitOffset DIV 32))</pre>
for a 32-bit operand size, or two bytes starting from the memory address given by: <br />
 
<pre>    Effective Address + (2 * (BitOffset DIV 16))</pre>
for a 16-bit operand size. It may do this even when only a single byte needs to be accessed in order to get at the given bit. You must therefore be careful to avoid referencing areas of memory close to address space holes. In particular, avoid references to memory-mapped I/O registers. Instead, use the MOV instructions to load from or store to these addresses, and use the register form of these instructions to manipulate the data.
 
[[[01605.htm|prev]]][[[01607.htm|next]]][[[01597.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01599.htm|Description]]
 
[[01601.htm|Flags Affected]]
 
[[01605.htm|Notes]]
 
[[01600.htm|Operation]]
 
[[01602.htm|Protected Mode Exceptions]]
 
[[01603.htm|Real Address Mode Exceptions]]
 
[[01604.htm|Virtual 8086 Mode Exceptions]]
 
[[[01606.htm|prev]]][[[01608.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CALL-Call Procedure ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|E8 cw    |CALL rel16          |X|X|X|X|X|X|Call near, displacement relative  |
|          |                    | | | | | | |to next instruction              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /2    |CALL r/m16          |X|X|X|X|X|X|Call near, register              |
|          |                    | | | | | | |indirect/memory indirect          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      |X|X|X|X|X|X|Call intersegment, to full pointer|
|          |                    | | | | | | |given                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call to task (via task state      |
|          |                    | | | | | | |segment/task gate for 286)        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        |X|X|X|X|X|X|Call intersegment, address at r/m |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call to task (via task state      |
|          |                    | | | | | | |segment/task gate for 286)        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|E8 cd    |CALL rel32          | | | |X|X|X|Call near, displacement relative  |
|          |                    | | | | | | |to next instruction              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /2    |CALL r/m32          | | | |X|X|X|Call near, register              |
|          |                    | | | | | | |indirect/memory indirect          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call intersegment, to full pointer|
|          |                    | | | | | | |given                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call to task                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call intersegment, address at r/m |
|          |                    | | | | | | |fword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call to task                      |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CALL instruction causes the procedure named in the operand to be run. When the procedure is complete (a return instruction is run within the procedure), processing continues at the instruction that follows the CALL instruction.
 
The action of the different forms of the instruction are described below.
 
Near calls are those with destination of type ''r/m16, r/m32, rel16, rel32''; changing or saving the segment register value is not necessary. The CALL ''rel16''and CALL ''rel32''forms add a signed offset to the address of the instruction following the CALL instruction to determine the destination. The ''rel16''form is used when the instruction's operand-size attribute is 16- bits; ''rel32''is used when the operand-size attribute is 32-bits. The result is stored in the 32-bit EIP register. With ''rel16'', the upper 16-bits of the EIP register are cleared, resulting in an offset whose value does not exceed 16-bits. CALL ''r/m16''and CALL ''r/m32''specify a register or memory location from which the absolute segment offset is fetched. The offset fetched from ''r/m''is 32-bits for an operand-size attribute of 32 (''r/m32''), or 16-bits for an operand-size of 16 (''r/m16''). The offset of the instruction following the CALL instruction is pushed onto the stack. It will be popped by a near RET instruction within the procedure. The CS register is not changed by this form of CALL.
 
The far calls, CALL ''ptr:16''and CALL ''ptr16:32'', use a four-byte or six-byte operand as a long pointer to the procedure called. The CALL ''m16:16''and ''m16: 32''forms fetch the long pointer from the memory location specified ( indirection). In Real Address Mode or Virtual 8086 Mode, the long pointer provides 16-bits for the CS register and 16 or 32-bits for the EIP register (depending on the operand-size attribute). These forms of the instruction push both the CS and IP or EIP registers as a return address.
 
In Protected Mode, both long pointer forms consult the AR byte in the descriptor indexed by the selector part of the long pointer. Depending on the value of the AR byte, the call will perform one of the following types of control transfers:
 
�A far call to the same protection level
 
�An inter-protection level far call
 
�A task switch <br />
 
A CALL-indirect-thru-memory, which uses the stack pointer (ESP) as a base register, references memory before the CALL. The base used is the value of the ESP before the instruction runs.
 
For more information on Protected Mode control transfers, refer to the Intel documentation.
 
 
-----
 
[[01609.htm|Description]]
 
[[01611.htm|Flags Affected]]
 
[[01615.htm|Notes]]
 
[[01610.htm|Operation]]
 
[[01612.htm|Protected Mode Exceptions]]
 
[[01613.htm|Real Address Mode Exceptions]]
 
[[01614.htm|Virtual 8086 Mode Exceptions]]
 
[[[01607.htm|prev]]][[[01609.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|E8 cw    |CALL rel16          |X|X|X|X|X|X|Call near, displacement relative  |
|          |                    | | | | | | |to next instruction              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /2    |CALL r/m16          |X|X|X|X|X|X|Call near, register              |
|          |                    | | | | | | |indirect/memory indirect          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      |X|X|X|X|X|X|Call intersegment, to full pointer|
|          |                    | | | | | | |given                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cd    |CALL ptr16:16      | | |X|X|X|X|Call to task (via task state      |
|          |                    | | | | | | |segment/task gate for 286)        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        |X|X|X|X|X|X|Call intersegment, address at r/m |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:16        | | |X|X|X|X|Call to task (via task state      |
|          |                    | | | | | | |segment/task gate for 286)        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|E8 cd    |CALL rel32          | | | |X|X|X|Call near, displacement relative  |
|          |                    | | | | | | |to next instruction              |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /2    |CALL r/m32          | | | |X|X|X|Call near, register              |
|          |                    | | | | | | |indirect/memory indirect          |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call intersegment, to full pointer|
|          |                    | | | | | | |given                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|9A cp    |CALL ptr16:32      | | | |X|X|X|Call to task                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call intersegment, address at r/m |
|          |                    | | | | | | |fword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, same privilege        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, more privilege, no    |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call gate, more privilege, x      |
|          |                    | | | | | | |parameters                        |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FF /3    |CALL m16:32        | | | |X|X|X|Call to task                      |
\------------------------------------------------------------------------------/</pre>
[[[01608.htm|prev]]][[[01610.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CALL instruction causes the procedure named in the operand to be run. When the procedure is complete (a return instruction is run within the procedure), processing continues at the instruction that follows the CALL instruction.
 
The action of the different forms of the instruction are described below.
 
Near calls are those with destination of type ''r/m16, r/m32, rel16, rel32''; changing or saving the segment register value is not necessary. The CALL ''rel16''and CALL ''rel32''forms add a signed offset to the address of the instruction following the CALL instruction to determine the destination. The ''rel16''form is used when the instruction's operand-size attribute is 16- bits; ''rel32''is used when the operand-size attribute is 32-bits. The result is stored in the 32-bit EIP register. With ''rel16'', the upper 16-bits of the EIP register are cleared, resulting in an offset whose value does not exceed 16-bits. CALL ''r/m16''and CALL ''r/m32''specify a register or memory location from which the absolute segment offset is fetched. The offset fetched from ''r/m''is 32-bits for an operand-size attribute of 32 (''r/m32''), or 16-bits for an operand-size of 16 (''r/m16''). The offset of the instruction following the CALL instruction is pushed onto the stack. It will be popped by a near RET instruction within the procedure. The CS register is not changed by this form of CALL.
 
The far calls, CALL ''ptr:16''and CALL ''ptr16:32'', use a four-byte or six-byte operand as a long pointer to the procedure called. The CALL ''m16:16''and ''m16: 32''forms fetch the long pointer from the memory location specified ( indirection). In Real Address Mode or Virtual 8086 Mode, the long pointer provides 16-bits for the CS register and 16 or 32-bits for the EIP register (depending on the operand-size attribute). These forms of the instruction push both the CS and IP or EIP registers as a return address.
 
In Protected Mode, both long pointer forms consult the AR byte in the descriptor indexed by the selector part of the long pointer. Depending on the value of the AR byte, the call will perform one of the following types of control transfers:
 
�A far call to the same protection level
 
�An inter-protection level far call
 
�A task switch <br />
 
A CALL-indirect-thru-memory, which uses the stack pointer (ESP) as a base register, references memory before the CALL. The base used is the value of the ESP before the instruction runs.
 
For more information on Protected Mode control transfers, refer to the Intel documentation.
 
[[[01609.htm|prev]]][[[01611.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF rel/16 or rel32 type of call
THEN (* near relative call *)
    IF OperandSize = 16
    THEN
      Push(IP);
      EIP � (EIP + rel16) AND 0000FFFFH;
    ELSE (* OperandSize = 32 *)
      Push(EIP);
      EIP � EIP + rel32;
    FI;
FI;
IF r/m16 or r/m32 type of call
THEN (* near absolute call *)
IF OperandSize = 16
    THEN
      Push(IP);
      EIP � [r/m16] AND 0000FFFFH;
    ELSE (*OperandSize = 32 *)
      Push(EIP);
      EIP �[r/m32]
    FI;
FI
 
IF (PE = 0 OR (PE = 1 AND VM = 1))
(* real mode or virtual 8086 mode *)
  AND instruction = far CALL
    (* i.e., operand type is m16:16, m16:32, ptr16:16, ptr16:32*)
THEN
    IF OperandSize = 16
    THEN
      Push(CS);
      Push(IP); (* address of next instruction; 16 bits *)
    ELSE
      Push(CS); (* padded with 16 high-order bits *)
      Push(EIP); (* address of next instruction; 32 bits *)
FI;
IF operand type is m16:16 or m16:32
THEN (* indirect far call *)
    IF OperandSize = 16
    THEN
      CS:IP � [m16:16];
    EIP � EIP AND 0000FFFFH; (* clear upper 16 bits *)
    ELSE (* OperandSize = 32 *)
      CS:EIP � [m16:32[;
    FI;
FI;
IF operand type is ptr:16 or ptr16:32
THEN (* direct far call *)
    IF OperandSize = 16
    THEN
      CS:IP � ptr:16;
      EIP � EIP AND 0000FFFFH; (* clear upper 16 bits *)
    ELSE (* OperandSize = 32 *)
      CS:EIP � ptr16:32;
    FI;
  FI;
FI;
 
IF (PE = 1 AND VM = 0) (* Protected mode, not V86 mode *)
  AND instruction = far CALL
THEN
  If indirect, then check access of EA doubleword;
    #GP(0) if limit violation;
  New CS selector must not be null else #GP(0);
  Check that new CS selector index is within its
    descriptor table limits; else #GP(new CS selector);
  Examine AR byte of selected descriptor for various legal values;
    depending on value:
    go to CONFORMING-CODE-SEGMENT;
    go to NONCONFORMING-CODE-SEGMENT;
    go to CALL-GATE;
    go to TASK-GATE;
    go to TASK-STATE-SEGMENT;
  ELSE #GP(code segment selector);
FI;
 
CONFORMING-CODE-SEGMENT:
  DPL must be ó CPL ELSE #GP(code segment selector);
  Segment must be present ELSE #NP(code segment selector);
  Stack must be big enough for return address ELSE #SS(0);
  Instruction pointer must be in code segment limit ELSE #GP(0);
  Load code segment descriptor into CS register;
  Load CS with new code segment selector;
  Load EIP with zero-extend(new offset);
  IF OperandSize=16 THEN EIP � EIP AND 0000FFFFH; FI;
 
NONCONFORMING-CODE-SEGMENT:
  RPL must be ó CPL ELSE #GP(code segment selector)
  DPL must be = CPL ELSE #GP(code segment selector)
  Segment must be present ELSE #NP(code segment selector)
  Stack must be big enough for return address ELSE #SS(0)
  Instruction pointer must be in code segment limit ELSE #GP(0)
  Load code segment descriptor into CS register
  Load CS with new code segment selector
  Set RPL of CS to CPL
  Load EIP with zero-extend(new offset);
  IF OperandSize=16 THEN EIP � EIP AND 0000FFFFH; FI;
 
  CALL-GATE
  Call gate DPL must be ò CPL ELSE #GP(call gate elector)
  Call gate DPL must be ò RPL ELSE #GP(call gate elector)
  Call gate just be present ELSE #NP(call gate selector)
  Examine code segment selector in call gate descriptor:
    Selector must not be null ELSE #GP(0)
    Selector must be within its descriptor table
      limits ELSE #GP(code segment selector)
    AR byte of selected descriptor must indicate code
      segment ELSE #GP(code segment selector)
    DPL of selected descriptor must be ó CPL ELSE
      #GP(code segment selector)
    IF non-conforming code segment AND DPL &lt; CPL
    THEN go to MORE-PRIVILEGE
    ELSE go to SAME-PRIVILEGE
    FI;
 
MORE-PRIVILEGE:
  Get new SS selector for new privilege level from TSS
    Check selector and descriptor for new SS:
      Selector must not be null ELSE #TS(0)
      Selector index must be within its descriptor
        table limits ELSE #TS(SS selector)
      Selector's RPL must equal DPL of code segment
        ELSE #TS(SS selector)
      Stack segment DPL must equal DPL of code
        segment ELSE #TS(SS selector)
      Descriptor must indicate writable data segment
        ELSE #TS(SS selector)
      Segment present ELSE #SS(SS selector)
IF OperandSize=32
  THEN
      New stack must have room for parameters plus 16 bytes
        ELSE #SS(SS selector)
      EIP must be in code segment limit ELSE #GP(0)
      Load new SS:eSP value from TSS
      Load new CS:EIP value from gate
  ELSE
    New stack must have room for parameters plus 8 bytes
      ELSE #SS(SS selector)
    IP must be in code segment limit ELSE #GP(0)
    Load new SS:eSP value from TSS
    Load new CS:IP value from gate
  FI;
  Load CS descriptor
  Load SS descriptor
  Push long pointer of old stack onto new stack
  Get word count from call gate, mask to 5 bits
  Copy parameters from old stack onto new stack
  Push return address onto new stack
  Set CPL to stack segment DPL
  Set RPL of CS to CPL
 
SAME-PRIVILEGE:
  IF OperandSize=32
  THEN
    Stack must have room for 6-byte return address (padded to 8 bytes)
      ELSE #SS(0)
    EIP must be within code segment limit ELSE #GP(0)
    Load CS:EIP from gate
  ELSE
    Stack must have room for 4-byte return address ELSE #SS(0)
    IP must be within code segment limit ELSE #GP(0)
    Load CS:IP from gate
FI;
Push return address onto stack
Load code segment descriptor into CS register
Set RPL of CS to CPL
 
TASK-GATE:
    Task gate DPL must be ó CPL ELSE #TS(gate selector)
    Task gate DPL must be ó RPL ELSE #TS(gate selector)
    Task Gate must be present ELSE #NP(gate selector)
    Examine selector to TSS, given in Task Gate descriptor:
      Must specify global in the local/global bit ELSE #TS(TSS selector)
      Index must be within GDT limits ELSE #TS(TSS selector)
      TSS descriptor AR byte must specify nonbusy TSS
        ELSE #TS(Tss selector)
      Task State Segment must be present ELSE #NP(TSS selector)
  SWITCH-TASKS (with nesting) to TSS
  IP must be in code segment limit ELSE #TS(0)
 
TASK-STATE-SEGMENT
  TSS DPL must be ó CPL ELSE #TS(TSS selector)
  TSS DPL must be ó RPL ELSE #TS(TSS selector)
  TSS descriptor AR byte must specify available TSS
    ELSE #TS(TSS selector)
  Task State Segment must be present ELSE #NP(TSS selector)
  SWITCH-TASKS (with nesting) to TSS
  IP must be in code segment limit ELSE #TS(0)</pre>
[[[01610.htm|prev]]][[[01612.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |  |
\-----------------------/</pre>
All flags are affected if a task switch occurs; no flags are affected if a task switch does not occur.
 
[[[01611.htm|prev]]][[[01613.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
For far calls: #GP, #NP, #SS, and #TS, as indicated in the &quot;Operation&quot; section.
 
For near direct calls: #GP(0) if procedure location is beyond the code segment limits; #SS(0) if pushing the return address exceeds the bounds of the stack segment; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
For a near indirect call: #GP(0) for an illegal memory operand effective address is the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #GP(0) if the indirect offset obtained is beyond the code segment limits; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01612.htm|prev]]][[[01614.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
 
[[[01613.htm|prev]]][[[01615.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
 
[[[01614.htm|prev]]][[[01616.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Notes ===
 
Any far call from a 32-bit code segment to a 16-bit code segment should be made from the first 64 Kbytes of the 32-bit code segment, because the operand-size attribute of the instruction is set to 16, allowing only a 16- bit return address offset to be saved.
 
[[[01615.htm|prev]]][[[01617.htm|next]]][[[01607.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01609.htm|Description]]
 
[[01611.htm|Flags Affected]]
 
[[01615.htm|Notes]]
 
[[01610.htm|Operation]]
 
[[01612.htm|Protected Mode Exceptions]]
 
[[01613.htm|Real Address Mode Exceptions]]
 
[[01614.htm|Virtual 8086 Mode Exceptions]]
 
[[[01616.htm|prev]]][[[01618.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CBW/CWDE-Convert Byte to Word/Convert Word to Doubleword ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|98        |CBW                |X|X|X|X|X|X|AX � sign extend of AL            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|98        |CWDE                | | | |X|X|X|EAX � sign-extend of AX          |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CBW instruction converts the signed byte in the AL register to a signed word in the AX register by extending the most significant bit of the AL register (the sign bit) into all of the bits of the AH register. The CWDE instruction converts the signed word in the AX register to a doubleword in the EAX register by extending the most significant bit of the AX register into the two most significant bytes of the EAX register. Note that the CWDE instruction is different from the CWD instruction. The CWD instruction uses the DX:AX register pair rather than the EAX register as a destination.
 
 
-----
 
[[01619.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01620.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01617.htm|prev]]][[[01619.htm|next]]][[[01617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|98        |CBW                |X|X|X|X|X|X|AX � sign extend of AL            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|98        |CWDE                | | | |X|X|X|EAX � sign-extend of AX          |
\------------------------------------------------------------------------------/</pre>
[[[01618.htm|prev]]][[[01620.htm|next]]][[[01617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CBW instruction converts the signed byte in the AL register to a signed word in the AX register by extending the most significant bit of the AL register (the sign bit) into all of the bits of the AH register. The CWDE instruction converts the signed word in the AX register to a doubleword in the EAX register by extending the most significant bit of the AX register into the two most significant bytes of the EAX register. Note that the CWDE instruction is different from the CWD instruction. The CWD instruction uses the DX:AX register pair rather than the EAX register as a destination.
 
[[[01619.htm|prev]]][[[01621.htm|next]]][[[01617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF OperandSize = 16 (* instruction = CBW *)
THEN AX � Sign Extend(AL);
ELSE (* OperandSize = 32, instruction = CWDE *)
  EAX � Sign Extend(AX);
FI;</pre>
[[[01620.htm|prev]]][[[01622.htm|next]]][[[01617.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01619.htm|Description]]
 
[[01470.htm|Flags Affected]]
 
[[01620.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01621.htm|prev]]][[[01623.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CDQ-Convert Double to Quad ===
 
See entry for CWD/CDQ-Convert Word to Double/Convert Double to Quad.
 
[[[01622.htm|prev]]][[[01624.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CLC-Clear Carry Flag ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|F8        |CLC                |X|X|X|X|X|X|Clear carry flag                  |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CLC instruction clears the CF flag. It does not affect other flags or registers.
 
 
-----
 
[[01625.htm|Description]]
 
[[01627.htm|Flags Affected]]
 
[[01626.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01623.htm|prev]]][[[01625.htm|next]]][[[01623.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|F8        |CLC                |X|X|X|X|X|X|Clear carry flag                  |
\------------------------------------------------------------------------------/</pre>
[[[01624.htm|prev]]][[[01626.htm|next]]][[[01623.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CLC instruction clears the CF flag. It does not affect other flags or registers.
 
[[[01625.htm|prev]]][[[01627.htm|next]]][[[01623.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � 0;</pre>
[[[01626.htm|prev]]][[[01628.htm|next]]][[[01623.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |0 |
\-----------------------/</pre>
The CF flag is cleared.
 
[[[01627.htm|prev]]][[[01629.htm|next]]][[[01623.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01625.htm|Description]]
 
[[01627.htm|Flags Affected]]
 
[[01626.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01628.htm|prev]]][[[01630.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CLD-Clear Direction Flag ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FC        |CLD                |X|X|X|X|X|X|Clear direction flag              |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CLD instruction clears the direction flag. No other flags or registers are affected. After a CLD instruction is run, string operations will increment the index registers (SI and/or DI) that they use.
 
 
-----
 
[[01631.htm|Description]]
 
[[01633.htm|Flags Affected]]
 
[[01632.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01629.htm|prev]]][[[01631.htm|next]]][[[01629.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FC        |CLD                |X|X|X|X|X|X|Clear direction flag              |
\------------------------------------------------------------------------------/</pre>
[[[01630.htm|prev]]][[[01632.htm|next]]][[[01629.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CLD instruction clears the direction flag. No other flags or registers are affected. After a CLD instruction is run, string operations will increment the index registers (SI and/or DI) that they use.
 
[[[01631.htm|prev]]][[[01633.htm|next]]][[[01629.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>DF � 0;</pre>
[[[01632.htm|prev]]][[[01634.htm|next]]][[[01629.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |0 |  |  |  |  |  |  |
\-----------------------/</pre>
The DF flag is cleared.
 
[[[01633.htm|prev]]][[[01635.htm|next]]][[[01629.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01631.htm|Description]]
 
[[01633.htm|Flags Affected]]
 
[[01632.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01634.htm|prev]]][[[01636.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CLI-Clear Interrupt Flag ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FA        |CLI                |X|X|X|X|X|X|Clear interrupt flag; interrupts  |
|          |                    | | | | | | |disabled when interrupt flag      |
|          |                    | | | | | | |cleared                          |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CLI instruction clears the IF flag if the current privilege level is at least as privileged as IOPL. No other flags are affected. External interrupts are not recognized at the end of the CLI instruction from that point on until the IF flag is set.
 
 
-----
 
[[01639.htm|Decision Table]]
 
[[01637.htm|Description]]
 
[[01640.htm|Flags Affected]]
 
[[01638.htm|Operation]]
 
[[01641.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01642.htm|Virtual 8086 Mode Exceptions]]
 
[[[01635.htm|prev]]][[[01637.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|FA        |CLI                |X|X|X|X|X|X|Clear interrupt flag; interrupts  |
|          |                    | | | | | | |disabled when interrupt flag      |
|          |                    | | | | | | |cleared                          |
\------------------------------------------------------------------------------/</pre>
[[[01636.htm|prev]]][[[01638.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CLI instruction clears the IF flag if the current privilege level is at least as privileged as IOPL. No other flags are affected. External interrupts are not recognized at the end of the CLI instruction from that point on until the IF flag is set.
 
[[[01637.htm|prev]]][[[01639.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>IF PE = 0
THEN
  IF �0;
ELSE
  IF VM = 0 (* Running in protected Mode *)
  THEN
      IF IOPL = 3
      THEN IF � 0;
      ELSE IF CPL ó IOPL
                THEN IF � 0;
                ELSE #GP(0);
                FI;
      FI;
  ELSE (* Running in Virtual-8086 mode *)
      IF IOPL = 3
      THEN IF �
      ELSE #GP(0);
      FI;
  FI;
FI;</pre>
[[[01638.htm|prev]]][[[01640.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Decision Table ===
 
The following decision table indicates which action in the lower portion of the table is taken given the conditions in the upper portion of the table. <br />
 
<pre>/--------------------------------------------------\
|PE =      |  0  |  1  |  1  |  1  |  1  |
|----------+-------+-------+-------+-------+-------|
|VM =      |  -  |  0  |  -  |  0  |  1  |
|----------+-------+-------+-------+-------+-------|
|CPL      |  -  |óIOPL  |  -  |&gt;IOPL  |  -  |
|----------+-------+-------+-------+-------+-------|
|IOPL      |  -  |  -  |  = 3  |  -  |  &lt; 3  |
|----------+-------+-------+-------+-------+-------|
|IF � 0    |  Y  |  Y  |  Y  |      |      |
|----------+-------+-------+-------+-------+-------|
|#GP(0)    |      |      |      |  Y  |  Y  |
\--------------------------------------------------/</pre>
'''Notes:'''
 
- Don't care
 
Blank Action Not Taken
 
Y Action in Column 1 taken <br />
 
[[[01639.htm|prev]]][[[01641.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |0 |  |  |  |  |  |
\-----------------------/</pre>
IF cleared.
 
[[[01640.htm|prev]]][[[01642.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the current privilege level is greater (has less privilege) than the I/O privilege level in the flags register. The I/O privilege level specifies the least privileged level at which I/O can be performed.
 
[[[01641.htm|prev]]][[[01643.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
#GP(0) as for protected mode.
 
[[[01642.htm|prev]]][[[01644.htm|next]]][[[01635.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01639.htm|Decision Table]]
 
[[01637.htm|Description]]
 
[[01640.htm|Flags Affected]]
 
[[01638.htm|Operation]]
 
[[01641.htm|Protected Mode Exceptions]]
 
[[01468.htm|Real Address Mode Exceptions]]
 
[[01642.htm|Virtual 8086 Mode Exceptions]]
 
[[[01643.htm|prev]]][[[01645.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CLTS-Clear Task-Switched Flag in CR0 ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F 06    |CLTS                | | |X|X|X|X|Clear task-switched flag          |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CLTS instruction clears the task-switched (TS) flag in the CR0 register . This flag is set by the processor every time a task switch occurs. The TS flag is used to manage processor extensions as follows:
 
�Every processing of an ESC instruction is trapped if the TS flag is set.
 
�Processing of a WAIT instruction is trapped if the MP flag and the TS flag are both set. <br />
 
Thus, if a task switch was made after an ESC instruction was begun, the floating-point unit's context may need to be saved before a new ESC instruction can be issued. The fault handler saves the context and clears the TS flag.
 
The CLTS instruction appears in operating system software, not in application programs. It is a privileged instruction that can only be run at privilege level 0.
 
 
-----
 
[[01646.htm|Description]]
 
[[01648.htm|Flags Affected]]
 
[[01647.htm|Operation]]
 
[[01649.htm|Protected Mode Exceptions]]
 
[[01650.htm|Real Address Mode Exceptions]]
 
[[01651.htm|Virtual 8086 Mode Exceptions]]
 
[[[01644.htm|prev]]][[[01646.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|0F 06    |CLTS                | | |X|X|X|X|Clear task-switched flag          |
\------------------------------------------------------------------------------/</pre>
[[[01645.htm|prev]]][[[01647.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CLTS instruction clears the task-switched (TS) flag in the CR0 register . This flag is set by the processor every time a task switch occurs. The TS flag is used to manage processor extensions as follows:
 
�Every processing of an ESC instruction is trapped if the TS flag is set.
 
�Processing of a WAIT instruction is trapped if the MP flag and the TS flag are both set. <br />
 
Thus, if a task switch was made after an ESC instruction was begun, the floating-point unit's context may need to be saved before a new ESC instruction can be issued. The fault handler saves the context and clears the TS flag.
 
The CLTS instruction appears in operating system software, not in application programs. It is a privileged instruction that can only be run at privilege level 0.
 
[[[01646.htm|prev]]][[[01648.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>TS Flag in CR0 � 0;</pre>
[[[01647.htm|prev]]][[[01649.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |  |
\-----------------------/</pre>
The TS flag is cleared (the TS flag is in the CR0 register, not the flags register).
 
[[[01648.htm|prev]]][[[01650.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Protected Mode Exceptions ===
 
#GP(0) if the CLTS instruction is run with a current privilege level other than 0.
 
[[[01649.htm|prev]]][[[01651.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Real Address Mode Exceptions ===
 
None (valid in Real Address Mode to allow initialization for Protected Mode ).
 
[[[01650.htm|prev]]][[[01652.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Virtual 8086 Mode Exceptions ===
 
Same exceptions as in Protected Mode.
 
[[[01651.htm|prev]]][[[01653.htm|next]]][[[01644.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01646.htm|Description]]
 
[[01648.htm|Flags Affected]]
 
[[01647.htm|Operation]]
 
[[01649.htm|Protected Mode Exceptions]]
 
[[01650.htm|Real Address Mode Exceptions]]
 
[[01651.htm|Virtual 8086 Mode Exceptions]]
 
[[[01652.htm|prev]]][[[01654.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CMC-Complement Carry Flag ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|F5        |CMC                |X|X|X|X|X|X|Complement carry flag            |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CMC instruction reverses the setting of the CF flag. No other flags are affected.
 
 
-----
 
[[01655.htm|Description]]
 
[[01657.htm|Flags Affected]]
 
[[01656.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Protected Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01653.htm|prev]]][[[01655.htm|next]]][[[01653.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|F5        |CMC                |X|X|X|X|X|X|Complement carry flag            |
\------------------------------------------------------------------------------/</pre>
[[[01654.htm|prev]]][[[01656.htm|next]]][[[01653.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CMC instruction reverses the setting of the CF flag. No other flags are affected.
 
[[[01655.htm|prev]]][[[01657.htm|next]]][[[01653.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>CF � NOT CF;</pre>
[[[01656.htm|prev]]][[[01658.htm|next]]][[[01653.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|  |  |  |  |  |  |  |* |
\-----------------------/</pre>
The CF flag contains the complement of its original value.
 
[[[01657.htm|prev]]][[[01659.htm|next]]][[[01653.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Related Information ===
 
[[01655.htm|Description]]
 
[[01657.htm|Flags Affected]]
 
[[01656.htm|Operation]]
 
[[01467.htm|Protected Mode Exceptions]]
 
[[01468.htm|Protected Mode Exceptions]]
 
[[01469.htm|Virtual 8086 Mode Exceptions]]
 
[[[01658.htm|prev]]][[[01660.htm|next]]][[[01466.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== CMP-Compare Two Operands ===
 
 
-----
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3C ib    |CMP AL,imm8        |X|X|X|X|X|X|Compare immediate byte to AL      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3D iw    |CMP AX,imm16        |X|X|X|X|X|X|Compare immediate word to AX      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3D id    |CMP EAX,imm32      | | | |X|X|X|Compare immediate dword to EAX    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /7 ib  |CMP r/m8,imm8      |X|X|X|X|X|X|Compare immediate byte to r/m byte|
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /7 iw  |CMP r/m16,imm16    |X|X|X|X|X|X|Compare immediate word to r/m word|
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /7 id  |CMP r/m32,imm32    | | | |X|X|X|Compare immediate dword to r/m    |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /7 ib  |CMP r/m16,imm8      |X|X|X|X|X|X|Compare sign-extended immediate  |
|          |                    | | | | | | |byte to r/m word                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /7 ib  |CMP r/m32,imm8      | | | |X|X|X|Compare sign-extended immediate  |
|          |                    | | | | | | |byte to r/m dword                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|38 /r    |CMP r/m8,r8        |X|X|X|X|X|X|Compare byte register to r/m byte |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|39 /r    |CMP r/m16,r16      |X|X|X|X|X|X|Compare word register to r/m word |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|39 /r    |CMP r/m32,r32      | | | |X|X|X|Compare dword register to r/m    |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3A /r    |CMP r8,r/m8        |X|X|X|X|X|X|Compare r/m byte to byte register |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3B /r    |CMP r16,r/m16      |X|X|X|X|X|X|Compare r/m word to word register |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3B /r    |CMP r32,r/m32      | | | |X|X|X|Compare r/m dword to dword        |
|          |                    | | | | | | |register                          |
\------------------------------------------------------------------------------/</pre>
 
-----
 
The CMP instruction subtracts the second operand from the first but, unlike the SUB instruction, does not store the result; only the flags are changed. The CMP instruction is typically used in conjunction with conditional jumps and the SETcc instruction. (Refer to Appendix D for the list of signed and unsigned flag tests provided.) If an operand greater than one byte is compared to an immediate byte, the byte value is first sign-extended.
 
 
-----
 
[[01661.htm|Description]]
 
[[01663.htm|Flags Affected]]
 
[[01662.htm|Operation]]
 
[[01664.htm|Protected Mode Exceptions]]
 
[[01665.htm|Real Address Mode Exceptions]]
 
[[01666.htm|Virtual 8086 Mode Exceptions]]
 
[[[01659.htm|prev]]][[[01661.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Details Table ===
 
<br />
 
<pre>/------------------------------------------------------------------------------\
|Encoding  |Instruction        |0|1|2|3|4|5|Description                      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3C ib    |CMP AL,imm8        |X|X|X|X|X|X|Compare immediate byte to AL      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3D iw    |CMP AX,imm16        |X|X|X|X|X|X|Compare immediate word to AX      |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3D id    |CMP EAX,imm32      | | | |X|X|X|Compare immediate dword to EAX    |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|80 /7 ib  |CMP r/m8,imm8      |X|X|X|X|X|X|Compare immediate byte to r/m byte|
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /7 iw  |CMP r/m16,imm16    |X|X|X|X|X|X|Compare immediate word to r/m word|
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|81 /7 id  |CMP r/m32,imm32    | | | |X|X|X|Compare immediate dword to r/m    |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /7 ib  |CMP r/m16,imm8      |X|X|X|X|X|X|Compare sign-extended immediate  |
|          |                    | | | | | | |byte to r/m word                  |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|83 /7 ib  |CMP r/m32,imm8      | | | |X|X|X|Compare sign-extended immediate  |
|          |                    | | | | | | |byte to r/m dword                |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|38 /r    |CMP r/m8,r8        |X|X|X|X|X|X|Compare byte register to r/m byte |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|39 /r    |CMP r/m16,r16      |X|X|X|X|X|X|Compare word register to r/m word |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|39 /r    |CMP r/m32,r32      | | | |X|X|X|Compare dword register to r/m    |
|          |                    | | | | | | |dword                            |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3A /r    |CMP r8,r/m8        |X|X|X|X|X|X|Compare r/m byte to byte register |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3B /r    |CMP r16,r/m16      |X|X|X|X|X|X|Compare r/m word to word register |
|----------+--------------------+-+-+-+-+-+-+----------------------------------|
|3B /r    |CMP r32,r/m32      | | | |X|X|X|Compare r/m dword to dword        |
|          |                    | | | | | | |register                          |
\------------------------------------------------------------------------------/</pre>
[[[01660.htm|prev]]][[[01662.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Description ===
 
The CMP instruction subtracts the second operand from the first but, unlike the SUB instruction, does not store the result; only the flags are changed. The CMP instruction is typically used in conjunction with conditional jumps and the SETcc instruction. (Refer to Appendix D for the list of signed and unsigned flag tests provided.) If an operand greater than one byte is compared to an immediate byte, the byte value is first sign-extended.
 
[[[01661.htm|prev]]][[[01663.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Operation ===
 
<br />
 
<pre>LeftSRC - SignExtend(RightSRC);
(* CMP does not store a result; its purpose is to set the flags *)</pre>
[[[01662.htm|prev]]][[[01664.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
 
=== Flags Affected ===
 
<br />
 
<pre>/-----------------------\
|OF|DF|IF|SF|ZF|AF|PF|CF|
|--+--+--+--+--+--+--+--|
|* |  |  |* |* |* |* |* |
\-----------------------/</pre>
The OF, SF, ZF, AF, PF, and CF flags are set according to the result.


[[[01663.htm|prev]]][[[01665.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
*[[ALP Programming Guide and Reference/Assembler Directives|Assembler Directives]]
*[[ALP Programming Guide and Reference/Processor Reference|Processor Reference]]


=== Protected Mode Exceptions ===
*[[ALP Programming Guide and Reference/Assembler Messages|Assembler Messages]]


#GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF( fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
==Return Codes==
When ALP completes, it passes a return code back to the program that invoked it. This return code shows whether ALP completed successfully or with an error.
The return codes are:
* 0 Normal program completion.
* 1 User-specified file not found.
* 2 Unexpected system error.
* 3 Terminated by user or operating system.
* 4 Syntax errors in input file.
* 5 Command line usage error.
* 6 Internal sanity check failure.
* 7 Error accessing ALP messages file.


[[[01664.htm|prev]]][[[01666.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
==Notices==
''October 1997''


=== Real Address Mode Exceptions ===
The following paragraph does not apply to the United Kingdom or any country where such provisions are inconsistent with local law:


Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH.
INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS". WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.


[[[01665.htm|prev]]][[[01667.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this publication at any time.


=== Virtual 8086 Mode Exceptions ===
It is possible that this publication may contain reference to, or information about, IBM products (machines and programs), programming, or services that are not announced in your country. Such references or information must not be construed to mean that IBM intends to announce such IBM products, programming, or services in your country.


Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault; #AC for unaligned memory reference if the current privilege level is 3.
Requests for technical information about IBM products should be made to your IBM authorized reseller or IBM marketing representative.
(C) Copyright International Business Machines Corporation 1995-1997. All rights reserved. Note to U.S. Government Users -- Documentation related to restricted rights -- Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.


[[[01666.htm|prev]]][[[01668.htm|next]]][[[01659.htm|parent]]][[[toc.htm|TOC]]]<br />
The [[#Processor Reference]] portion of this manual contains information reprinted with permission from Intel Corporation.


=== Related Information ===
===Disclaimers===
References in this publication to IBM products, programs, or services do not imply that IBM intends to make these available in all countries in which IBM operates. Any reference to an IBM product, program or service is not intended to state or imply that only IBM's product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any of IBM's intellectual property rights or other legally protectable rights may be used instead of the IBM product, program, or service. Evaluation and verification of operation in conjunction with other products, programs, or services, except those expressly designated by IBM, are the user's responsibility.


[[01661.htm|Description]]
IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to the IBM Director of Licensing, IBM Corporation, 500 Columbus Avenue, Thornwood NY 10594, U.S.A.


[[01663.htm|Flags Affected]]
===Trademarks===
The following terms are trademarks of the IBM Corporation in the United States or other countries:
: IBM
: Operating System/2
: OS/2
: Presentation Manager


[[01662.htm|Operation]]
The following terms are trademarks of other companies:
: Microsoft - Microsoft Corporation
: Pentium - Intel Corporation Pentium Pro - Intel Corporation
: UNIX - UNIX System Laboratories, Inc.


[[01664.htm|Protect
[[Category:Online Books]]

Latest revision as of 20:50, 14 June 2022

Reprint Courtesy of International Business Machines Corporation, © International Business Machines Corporation

About this Reference

The following notations are used in this reference:

KEYWORD Commands and language keywords.
KEYWORD The default value for a command or language keyword when multiple values are possible but none are actually specified.
Phrase Typically indicates a hypertext link to a separate panel containing a description for that phrase.
Parameter Parameters whose actual names or values are to be supplied by the programmer.
Definition A term being defined for the first time, or special emphasis.
Subscript Subscripted text.
Superscript Superscripted text (other than ý).
<Name> A text value represented by "Name" is to be substituted in place of <Name> typically at assembler run-time.

Assembly Language Processor (ALP) Overview

The Assembly Language Processor (ALP) is an assembler that runs under OS/2 Warp. ALP is a functional replacement for the Microsoft Macro Assembler (MASM) and accepts:

  • The full syntax of the Intel 80X86 architecture
  • The full syntax of the MASM 5.10 high-level directive language
  • A subset of the MASM 6.00 high-level directive language

ALP generates standard Object Module Format (OMF) files that can be linked to produce DOS or OS/2 executables. It can also generate symbolic debugging information compatible with the IBM family of source code debuggers. A MASM 5.10-compatible command line utility (MASM2ALP) is also provided to enable use of ALP with little or no change to existing build environments.

ALP also offers a rich set of command line options, as well as a comprehensive listing output cabability that is highly configurable, allowing a visual perspective not possible with other assemblers.

Language Elements

Description

The following sections describe the elements you use to build an ALP program source file.

Character Set

All elements in an assembler language source file are built from collections of characters contained in the character set, which are defined as:

  • The uppercase and lowercase letters of the English alphabet
  • The decimal digits 0 through 9
  • The following graphic characters:
~   !   "   #   $   %   ^   &   '   (   )   | 
*   +   ,   -   .   /   :   ;   =   <   >   ? 
[   \   ]   _   {   }   @
  • The space and horizontal tab characters
  • The end of line character(s)

White Space

White space is a character or contiguous stream of characters that is ignored or removed from the input stream by the ALP preprocessor.

White space characters are any contiguous sequence of one or more space or tab characters not enclosed in single or double quotes. White space characters are significant only in that they serve to separate language tokens from one another; they are removed from the input stream by the scanner.

Syntax

Token:

Reserved-Word
Identifier
Literal
Punctuator

Reserved Words

Description

This section describes all of the assembler reserved words.

Syntax

Reserved-Word:

Preprocessor-Directive
Assembler-Directive
Processor-Mnemonic
Processor-Register
Scalar-TypeName
Distance-TypeName
Language-Name
Anonymous-Label-Alias
Location-Counter-Alias
Indeterminate-Value-Alias
Directive-Keyword
Operator-Keyword

Preprocessor Directives

Description

Preprocessor Directives are symbolic names that describe the various assembly-time text processing instructions interpreted by the preprocessor phase of the assembler.

Syntax

Preprocessor-Directive: one of 

CATSTR      COMMENT     ELSE        ELSEIF
ELSEIF1     ELSEIF2     ELSEIFB     ELSEIFDEF
ELSEIFDIF   ELSEIFDIFI  ELSEIFE     ELSEIFIDN
ELSEIFIDNI  ELSEIFNB    ELSEIFNDEF  ENDIF
ENDM        EQU         EXITM       FOR
FORC        IF          IF1         IF2
IFB         IFDEF       IFDIF       IFDIFI
IFE         IFIDN       IFIDNI      IFNB
IFNDEF      INCLUDE     INSTR       IRP
IRPC        LOCAL       MACRO       PURGE
REPEAT      REPT        SIZESTR     SUBSTR

Assembler Directives

Description

Assembler Directives are symbolic names that describe the various assembly-time instructions interpreted by the assembler itself.

Syntax

Assembler-Directive: one of 

.186          .286          .286C         .286P
.287          .386          .386C         .386P
.387          .486          .486C         .486P
.586          .586P         .686          .686P
.8086         .8087          ALIGN        .ALPHA
 ASSUME       %BIN          .CODE          COMM
.CONST        .CREF         .DATA         .DATA?
 DB            DD            DF            DOSSEG
.DOSSEG        DQ            DT            DW
 ECHO          END           ENDP          ENDS
 EQU          .ERR          .ERR1         .ERR2
.ERRB         .ERRDEF       .ERRDIF       .ERRDIFI
.ERRE         .ERRIDN       .ERRIDNI      .ERRNB
.ERRNDEF      .ERRNZ         EVEN          EXTERN
 EXTERNDEF     EXTRN        .FARDATA      .FARDATA?
 GROUP         INCLUDELIB    LABEL        .LALL
.LFCOND       .LIST         .LISTALL      .LISTIF
.LISTMACRO    .LISTMACROALL  LOCAL        .MMX
.MODEL         NAME         .NOCREF       .NOLIST
.NOLISTIF     .NOLISTMACRO  .NOMMX         OPTION
 ORG          %OUT           PAGE          PROC
 PUBLIC       .RADIX         RECORD       .SALL
 SEGMENT      .SEQ          .SFCOND       .STACK
 STRUC         STRUCT        SUBTITLE      SUBTTL
.TFCOND        TITLE         TYPEDEF       UNION
.XALL         .XCREF        .XLIST

Processor Mnemonics

Description

Processor Mnemonics are symbolic names given to the various instructions in the processor instruction set.

Syntax

Processor-Mnemonic: one of 

AAA        AAD        AAM        AAS        ADC
ADD        AND        ARPL       BOUND      BSF
BSR        BSWAP      BT         BTC        BTR
BTS        CALL       CBW        CDQ        CLC
CLD        CLI        CLTS       CMC        CMOVA
CMOVAE     CMOVB      CMOVBE     CMOVC      CMOVE
CMOVG      CMOVGE     CMOVL      CMOVLE     CMOVNA
CMOVNAE    CMOVNB     CMOVNBE    CMOVNC     CMOVNE
CMOVNG     CMOVNGE    CMOVNL     CMOVNLE    CMOVNO
CMOVNP     CMOVNS     CMOVNZ     CMOVO      CMOVP
CMOVPE     CMOVPO     CMOVS      CMOVZ      CMP
CMPS       CMPSB      CMPSD      CMPSW      CMPXCHG
CMPXCHG8B  CPUID      CWD        CWDE       DAA
DAS        DEC        DIV        EMMS       ENTER
ESC        F2XM1      FABS       FADD       FADDP
FBLD       FBSTP      FCHS       FCLEX      FCMOVB
FCMOVBE    FCMOVE     FCMOVNB    FCMOVNBE   FCMOVNE
FCMOVNU    FCMOVU     FCOM       FCOMI      FCOMIP
FCOMP      FCOMPP     FCOS       FDECSTP    FDISI
FDIV       FDIVP      FDIVR      FDIVRP     FENI
FFREE      FIADD      FICOM      FICOMP     FIDIV
FIDIVR     FILD       FIMUL      FINCSTP    FINIT
FIST       FISTP      FISUB      FISUBR     FLD
FLD1       FLDCW      FLDENV     FLDENVD    FLDENVW
FLDL2E     FLDL2T     FLDLG2     FLDLN2     FLDPI
FLDZ       FMUL       FMULP      FNCLEX     FNDISI
FNENI      FNINIT     FNOP       FNSAVE     FNSAVED
FNSAVEW    FNSTCW     FNSTENV    FNSTENVD   FNSTENVW
FNSTSW     FPATAN     FPREM      FPREM1     FPTAN
FRNDINT    FRSTOR     FRSTORD    FRSTORW    FSAVE
FSAVED     FSAVEW     FSCALE     FSETPM     FSIN
FSINCOS    FSQRT      FST        FSTCW      FSTENV
FSTENVD    FSTENVW    FSTP       FSTSW      FSUB
FSUBP      FSUBR      FSUBRP     FTST       FUCOM
FUCOMI     FUCOMIP    FUCOMP     FUCOMPP    FWAIT
FXAM       FXCH       FXTRACT    FYL2X      FYL2XP1
HLT        IDIV       IMUL       IN         INC
INS        INSB       INSD       INSW       INT
INTO       INVD       INVLPG     IRET       IRETD
IRETDF     IRETF      JA         JAE        JB
JBE        JC         JCXZ       JE         JECXZ
JG         JGE        JL         JLE        JMP
JNA        JNAE       JNB        JNBE       JNC
JNE        JNG        JNGE       JNL        JNLE
JNO        JNP        JNS        JNZ        JO
JP         JPE        JPO        JS         JZ
LAHF       LAR        LDS        LEA        LEAVE 
LES        LFS        LGDT       LGS        LIDT 
LLDT       LMSW       LOCK       LODS       LODSB 
LODSD      LODSW      LOOP       LOOPD      LOOPE 
LOOPED     LOOPEW     LOOPNE     LOOPNED    LOOPNEW 
LOOPNZ     LOOPNZD    LOOPNZW    LOOPW      LOOPZ 
LOOPZD     LOOPZW     LSL        LSS        LTR 
MOV        MOVD       MOVQ       MOVS       MOVSB 
MOVSD      MOVSW      MOVSX      MOVZX      MUL 
NEG        NOP        NOT        OR         OUT 
OUTS       OUTSB      OUTSD      OUTSW      PACKSSDW 
PACKSSWB   PACKUSWB   PADDB      PADDD      PADDSB 
PADDSW     PADDUSB    PADDUSW    PADDW      PAND 
PANDN      PCMPEQB    PCMPEQD    PCMPEQW    PCMPGTB 
PCMPGTD    PCMPGTW    PMADDWD    PMULHW     PMULLW 
POP        POPA       POPAD      POPD       POPF 
POPFD      POPW       POR        PSLLD      PSLLQ 
PSLLW      PSRAD      PSRAW      PSRLD      PSRLQ 
PSRLW      PSUBB      PSUBD      PSUBSB     PSUBSW 
PSUBUSB    PSUBUSW    PSUBW      PUNPCKHBW  PUNPCKHDQ 
PUNPCKHWD  PUNPCKLBW  PUNPCKLDQ  PUNPCKLWD  PUSH 
PUSHA      PUSHAD     PUSHD      PUSHF      PUSHFD 
PUSHW      PXOR       RCL        RCR        RDMSR 
RDPMC      RDTSC      REP        REPE       REPNE 
REPNZ      REPZ       RET        RETF       RETN 
ROL        ROR        RSM        SAHF       SAL 
SAR        SBB        SCAS       SCASB      SCASD 
SCASW      SETA       SETAE      SETB       SETBE 
SETC       SETE       SETG       SETGE      SETL 
SETLE      SETNA      SETNAE     SETNB      SETNBE 
SETNC      SETNE      SETNG      SETNGE     SETNL 
SETNLE     SETNO      SETNP      SETNS      SETNZ 
SETO       SETP       SETPE      SETPO      SETS 
SETZ       SGDT       SHL        SHLD       SHR 
SHRD       SIDT       SLDT       SMSW       STC 
STD        STI        STOS       STOSB      STOSD 
STOSW      STR        SUB        TEST       UC2 
VERR       VERW       WAIT       WBINVD     WRMSR 
XADD       XCHG       XLAT       XLATB      XOR

Processor Registers

Description

Processor Registers are the symbolic names assigned to the various internal processor registers. They are normally used as operands to processor instructions.

Syntax

Processor-Register:

General-Purpose-Register
Segment-Register
Control-Register
Debug-Register
Test-Register
MMX-Register
Floating-Point-Register

General-Purpose-Register:

8-Bit-Register
16-Bit-Register
32-Bit-Register

8-Bit-Register: one of

AL AH BL BH CL CH DL DH

16-Bit-Register: one of

AX BX CX DX DI SI BP SP

32-Bit-Register: one of

EAX EBX ECX EDX EDI ESI EBP ESP

Segment-Register: one of

CS DS ES FS GS SS

Control-Register: one of

CR0 CR2 CR3 CR4

Debug-Register: one of

DR0 DR1 DR2 DR3 DR4 DR5 DR6 DR7

Test-Register: one of

TR3 TR4 TR5 TR6 TR7

MMX-Register: one of

MM0 MM1 MM2 MM3 MM4 MM5 MM6 MM7

Floating-Point-Register: ST

Scalar Type Names

Description

Scalar Type Names are the symbolic names given to the integral data types. These are the fundamental types of data upon which the processor can directly operate.

Syntax

Scalar-TypeName:

BYTE
SBYTE
WORD
SWORD
DWORD
SDWORD
REAL4
FWORD
QWORD
REAL8
TBYTE
REAL10

Distance Type Names

Description

Distance Type Names are the symbolic names given to the integral types of pointers directly supported by the processor. Their names reflect a fundamental property of the Intel processor architecture known as distance. The type of pointer is defined by the distance required to reach the information to which it points.

Syntax

Distance-TypeName:

NEAR
NEAR16
NEAR32
FAR
FAR16
FAR32

Language Names

Description

Language Names refer to the various high level programming languages (or more specifically, the calling conventions used by such languages) with which the assembler has the ability to interface.

Syntax

Language-Name:

C
SYSCALL
STDCALL
PASCAL
FORTRAN
BASIC
OPTLINK

Anonymous Label Aliases

Description

The Anonymous Label Aliases are reserved symbolic names that return a context-sensitive value when referenced in expressions.

The reserved name @B (backward reference) returns the internally generated name representing the nearest @@: code label appearing before the current location in the input stream.

The reserved name @F (forward reference) returns the internally generated name representing the nearest @@: code label appearing after the current location in the input stream.

Syntax

Anonymous-Label-Alias:

@B
@F

Location Counter Alias

Description

The Location Counter Alias is a reserved name used in expressions to return the offset within the current segment or structure being assembled.

Syntax

Location-Counter-Alias:

$

Indeterminate Value Alias

Description

The Indeterminate Value Alias is a reserved name used in expressions to represent an uninitialized value.

Syntax

Indeterminate-Value-Alias:

?

Directive Keywords

Description

Directive Keywords are symbolic names recognized and used in the body of various assembler directives.

Syntax

Directive-Keyword: 

ABS         AT            BASIC         C
CASEMAP     CODE          COMMON        DOTNAME
EMULATOR    EPILOGUE      ERROR         EXPORT
EXPR16      EXPR32        FARSTACK      FLAT
FORTRAN     HUGE          LANGUAGE      LARGE
LJMP        MEDIUM        NEARSTACK     NODOTNAME
NOEMULATOR  NOKEYWORD     NOLANGUAGE    NOLJMP
NONE        NOOLDMACROS   NOOLDSTRUCTS  NOREADONLY
NOSCOPED    NOSIGNEXTEND  NOTHING       NOTPUBLIC
OLDMACROS   OLDSTRUCTS    OPTLINK       OS_DOS
OS_OS2      PAGE          PARA          PASCAL
PRIVATE     PROC          PROLOGUE      PUBLIC
READONLY    SCOPED        SEGMENT       SIGNEXTEND
SMALL       STACK         STDCALL       SYSCALL
TINY        USE16         USE32         USES

Operator Keywords

Description

Operator Keywords are symbolic names used in expressions to denote an operation to be performed on one or more operands.

Syntax

Operator-Keyword: 

AND         DUP         EQ          GE
GT          HIGH        HIGHWORD    LE
LENGTH      LENGTHOF    LOW         LOWWORD
LT          MASK        MOD         NE
NOT         OFFSET      OPATTR      OR
PTR         SEG         SHL         SHORT
SHR         SIZE        SIZEOF      THIS
.TYPE       TYPE        WIDTH       XOR

Identifiers

Description

This section describes the syntax for identifiers and the various types of information they can be made to represent.

Syntax

Identifier:

Normal-Identifier
Dot-Identifier
Normal-Identifier
NonDigit
Normal-Identifier Identifer-Character

Dot-Identifier . Normal-Identifier

Identifier-Character NonDigit Digit

NonDigit: one of 

_ $ @ ?
a b c d e f g h i j k l m
n o p q r s t u v w x y z
A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z

Digit: one of 

0 1 2 3 4 5 6 7 8 9

Identifier Types

Description

This section describes the various types of identifiers that the assembler will create and manipulate.

Definition

Identifier-Type:

EquateName
FieldName
GroupName
LabelName
MacroName
SegmentName
UserDefined-TypeName
Equate Name
Definition

EquateName:

Numeric-EquateName
Text-EquateName
Description

An EquateName is a symbolic identifier that is associated with an expression or a body of text. The assembler substitutes the value of the EquateName at the point of reference.

Numeric Equate Name

An identifier becomes a Numeric-EquateName when it is defined in a EQU or = directive. Procedure parameter names and local variable names are also created as Numeric-EquateNames, but are visible only from within the procedure where they are defined. All other Numeric-EquateNames are globally-scoped identifiers visible across the entire module.

A Numeric-EquateName may only be referenced from within expressions, as its replacement value is itself an expression.

Text Equate Name

A Text-EquateName is a globally-scoped identifier created during the processing of a EQU preprocessor directive. A Text-EquateName is associated with a body of text whose content may not span across line breaks. In certain contexts the assembler replaces the Text-EquateName with the text that it represents and recursively evaluates the result.

Field Name
Definition

FieldName:

Record-FieldName
Structure-FieldName
Union-FieldName
Description

An identifier becomes a FieldName when it is defined within a RECORD, STRUCT, or UNION directive.

Record Field Name

A Record-FieldName is a globally-scoped identifier created during the processing of a RECORD directive. It is a special variation of a Numeric-EquateName and can be used in the same contexts.

Structure Field Name

An identifier becomes a Structure-FieldName when it is defined in a STRUCT directive. If the assembler is operating in M510 mode, or if the OPTION OLDSTRUCTS directive has been specified, then a Structure-FieldName is a globally-scoped identifier treated as a special variation of a Numeric-EquateName and can be used in the same contexts. Otherwise, a Structure-FieldName is private to the defining structure and is only accessible in expressions through use of the Structure/Union Field Selection (. Operator).

Union Field Name

An identifier becomes a Union-FieldName when it is defined in a UNION directive. A Union-FieldName is private to the defining union and is only accessible in expressions through use of the Structure/Union Field Selection (. Operator).

Group Name

A GroupName is a globally-scoped identifier created during the processing of a GROUP directive. It is referenced from within expressions.

Label Name
Definition

LabelName:

Code-LabelName
Data-LabelName
Description

A LabelName is globally-scoped identifier that is associated with a program address at application run-time. It has an explicit or inherited Type-Declaration, and an optional Language-Attribute. These attributes are described in the following sections.

Type Declaration

The type declaration associated with a label name depends on how the label was defined. See the Code-LabelName and Data-LabelName sections for descriptions on how this attribute is assigned.

Language Attribute

A LabelName can have an assigned Language-Attribute, set either implicitly through the use of a Language-Name keyword in the body of a .MODEL or OPTION directive, or explicitly through the use of an overriding Language-Name keyword in the body of a EXTERN/EXTRN, EXTERNDEF, PROC, or PUBLIC directive. The Language-Attribute determines the exact spelling of the LabelName identifier when it is written to the object file. According to the Language-Attribute, identifier spellings are modified from their appearance in the assembly language source module as follow:

LANGUAGE ATTRIBUTE IDENTIFIER SPELLING
OPTLINK, SYSCALL No modifications are made to the identifier when written to the object file.
C, STDCALL A leading underscore character is appended to the front of the name.
BASIC, FORTRAN, PASCAL All characters in the identifier are converted to uppercase.
Code Label Name
Definition

Code-LabelName:

Target-LabelName
Procedure-LabelName
Description

A Code-LabelName is an identifier that is associated with an executable code address at application run-time. There are two types of Code-LabelNames: Target-LabelNames and Procedure-LabelNames.

Target Label Name

An identifier becomes a Target-LabelName when it is defined with a :, ::, or LABEL directive.

If a Target-LabelName created with a single colon (:) is defined within the body of a procedure, then the name is visible only from within that procedure unless operating in M510 mode (and no .MODEL directive with a Language-Name has been specified), or unless the OPTION NOSCOPED directive has been specified.

A Target-LabelName defined outside the body of a procedure is visible to the entire module, and may also be given PUBLIC visibility.

Procedure Label Name

An identifier becomes a Procedure-LabelName when it is defined in a PROC directive.

Data Label Name

A Data-LabelName is an identifier that is the address of a program variable at application run-time. An identifier becomes a Data-LabelName when it is named in a data allocation statement, or when a scalar, aggregate, or vector type is associated with the identifier named in a LABEL, EXTERN/ EXTRN, EXTERNDEF, or COMM directive.

Macro Name

A MacroName is a globally-scoped identifier created during the processing of a MACRO directive. It is associated with a multi-line body of text. A MacroName may only be used in contexts where a normal assembler directive is expected.

Macro Parameter Name

An identifier becomes a Macro-ParameterName when it is named as a parameter to a macro in a MACRO directive. It is associated with a body of text whose content may not span across line breaks. It is only recognized and acted upon from within the body of a macro expansion.

Segment Name

A SegmentName is a globally-scoped identifier created during the processing of a SEGMENT directive. It may be referenced from within expressions or in the body of a GROUP directive.

User-Defined Type Name

Definition

UserDefined-TypeName:

Record-TypeName
Structure-TypeName
Typedef-TypeName
Union-TypeName
Description

An identifier becomes a UserDefined-TypeName when it is defined within a RECORD, STRUCT, TYPEDEF, or UNION directive.

Record Type Name

A Record-TypeName is a globally-scoped identifier created during the processing of a RECORD directive. It is recognized from within Expressions, Type-Declarations, or as a pseudo-directive in a data allocation statement.

Structure Type Name

A Structure-TypeName is a globally-scoped identifier created during the processing of a STRUCT directive. It is recognized from within Expressions, Type-Declarations, or as a pseudo-directive in a data allocation statement.

Typedef Type Name

A Typedef-TypeName is a globally-scoped identifier created during the processing of a TYPEDEF directive. It is recognized from within Expressions, Type-Declarations, or as a pseudo-directive in a data allocation statement.

Union Type Name

A Union-TypeName is a globally-scoped identifier created during the processing of a UNION directive. It is recognized from within Expressions, Type-Declarations, or as a pseudo-directive in a data allocation statement.

Predefined Identifiers

The following sections describe the predefined identifiers created by the assembler. When a case-sensitive assembly is being performed, the predefined identifiers must be spelled exactly as they appear in the following descriptions with respect to uppercase and lowercase characters.

Segment Information

The following sections describe the predefined identifiers created by the assembler in support of segment manipulation.

@code

The @code identifier is a Text-EquateName created by the assembler when a .MODEL directive is encountered, at which time the assembler performs an automatic ASSUME CS:@code operation. The @code symbol is not defined if a .MODEL directive has not been issued.

Under MASM 5.10 emulation, the @code symbol is set to the name of the implicitly-defined default code segment (the segment opened when a .CODE directive is used) and its value is never changed. In other modes, the @code symbol is updated to reflect whatever segment is opened by using .CODE, whether defined implicitly or as an explicit parameter to the .CODE directive.

The value assigned to the @code symbol when the default code segment is opened is determined by the memory model as follows:

Memory Model Value for @code

TINY DGROUP
SMALL _TEXT
MEDIUM module _TEXT
COMPACT_TEXT
LARGE module _TEXT
HUGE module _TEXT
FLAT CODE32

The module entry is replaced with base file name of the top-level module being assembled.

@CodeSize

The @CodeSize identifier is a Numeric-EquateName created by the assembler when a .MODEL directive is encountered. @CodeSize indicates whether code segments created by the .CODE directive are named such that the linker will combine them into a single (NEAR) segment or into multiple (FAR) segments. The @CodeSize symbol is set to 0 (NEAR) for the TINY, SMALL, COMPACT, and FLAT memory models, and to 1 (FAR) for the MEDIUM, LARGE, and HUGE memory models. The @CodeSize symbol is not defined if a .MODEL directive has not been issued.

@CurSeg

The @CurSeg identifier is a Text-EquateName defined by the assembler to hold the name of the currently opened segment. If no segment is currently open, @CurSeg will expand into an empty string.

@data

The @data identifier is a Text-EquateName created by the assembler when a .MODEL directive is encountered. It expands to the group name shared by all of the near data segments. If a .MODEL FLAT has been issued, the @data identifier expands to FLAT. For all other memory models, it expands to DGROUP.

@DataSize

The @DataSize identifier is a Numeric-EquateName created by the assembler when a .MODEL directive is encountered, and represents the default data distance. Depending on the currently selected memory model, the @DataSize identifier is set to the following values:

TINY 0
SMALL 0
COMPACT 1
MEDIUM 1
LARGE 1
HUGE 2
FLAT 0
@Model

The @Model identifier is a Numeric-EquateName created by the assembler when a .MODEL directive is encountered, and is set to a unique value for each memory model. The values are as follows:

TINY 1
SMALL 2
COMPACT 3
MEDIUM 4
LARGE 5
HUGE 6
FLAT 7
@WordSize

The @WordSize identifier is a Numeric-EquateName that reflects the address size attribute of the current segment. It is set to 2 for a USE16 segment, and 4 for a USE32 segment. If no segment is currently open, it reflects the default address size as determined by the currently selected processor.

Version Information

These identifiers offer methods of testing the various operating modes of the assembler to determine what features are activated or disabled, or how the assembler will behave under various conditions.

@Alp

The @Alp identifier is a Text-EquateName that can be tested to determine if ALP is assembling the source file (versus some other assembler). It is always set to the string 100.

@AlpMajor

The @AlpMajor identifier is a Text-EquateName that reflects the major portion of the three-part assembler version number. It is padded on the right with zeros to allow major version number comparisions independant of the minor version and revisions numbers. See @AlpVersion for more information.

This identifier is only defined in ALP mode.

@AlpMinor

The @AlpMinor identifier is a Text-EquateName that reflects the minor portion of the three-part assembler version number. It is padded on the right with zeros to allow minor version number comparisions independant of the major version and revisions numbers. See @AlpVersion for more information.

This identifier is only defined in ALP mode.

@AlpRevision

The @AlpRevision identifier is a Text-EquateName that reflects the revision portion of the three-part assembler version number. It allows revision number comparisions independant of the major and minor version numbers. See @AlpVersion for more information.

This identifier is only defined in ALP mode.

@AlpVersion

The @AlpVersion identifier is a Text-EquateName that reflects the full three-part assembler version number. This is an encoding of the version number printed in the program banner when the assembler is invoked. This number and its requisite parts may be tested to determine the presence or absence of features provided by the assembler.

The assembler version number consists of three parts:

  1. The major version number (one digit)
  2. The minor version number (two digits)
  3. The revision number (three digits)

In the assembler banner, the numbers are separated by the period (.) character; the period is removed from the text defined by the predefined identifiers.

For example, if the major version number is 1, the minor version number is 2, and the revision number is 3, then the full version number is printed in the assembler banner as 1.02.003, and the various predefined version identifers would be set as follows: 

@AlpVersion   102003
@AlpMajor     100000
@AlpMinor       2000
@AlpRevision     003

This identifier is only defined in ALP mode.

@Cpu

The @Cpu identifier is a Numeric-EquateName that reflects the currently selected processor for which ALP is assembling instructions. This value is affected by issuing a Processor-Control-Directive, and is a bit map that indicates the currently active processor instruction set(s).

B A 9 8 7 6 5 4 3 2 1 0 BIT SET IF ASSEMBLING FOR
1 8086/8088
1 80186
1 80286
1 80386
1 80486
1 80586 (Pentium)
1 80686 (Pentium Pro)
1 Privileged mode
1 8087
1 MMX Extensions
1 80287
1 80387
@Version

The @Version identifier is a Text-EquateName that reflects the MASM-compatible version number. The current emulation mode of the assembler affects the value of this symbol as follows:

M510 510
M600 600
ALP 4294967295 (the highest possible value for an unsigned 32-bit integer)

Date and Time Information

These identifiers allow the programmer to query the system date or time during the assembly. Each time they are referenced, a new system request for the current date and time is made and the values held in the identifiers are refreshed.

@Date

The @Date identifier is a Text-EquateName that is set to the current system date. If the current operating mode is M600, the date is returned in the MM/DD/YY format. In native ALP mode, the date is returned in the MM/DD/YYYY format.

The @Date identifier is not available in M510 mode.

@Time

The @Time identifier is a Text-EquateName that is set to the current system time in 24-hour HH:MM:SS format.

The @Time identifier is not available in M510 mode.

File Information

These identifiers return information about the file(s) being assembled.

@FileName

The @FileName identifier is a Text-EquateName that is set to the base name of the main file being assembled (as it appears on the command line).

@Line

The @Line identifier is a Numeric-EquateName that is set to the current source line number in the file currently being assembled.

The @Line identifier is not available in M510 mode.

Literals

Description

Literals are the notational method whereby numeric values or strings of character data are represented in the source stream. Literals are also commonly referred to as constants (especially in the context of high level languages) because they typically represent objects whose values do not change throughout the life of the assembly or compilation. However, literals should not be confused with run-time "constants"; ("read-only"; data items allocated by the programmer); they are assembly-time tokens used by the assembler to represent numeric values or character strings.

Syntax

Literal:

Floating-Point-Literal
Integer-Literal
String-Literal

Integer Literals

Description

An integer literal represents a fixed-point numeric value. An integer literal must begin with one of the numeric digits 0 - 9, and may be optionally terminated with a suffix character called a radix specifier. The radix specifier tells the assembler whether the literal is to be interpreted as a base 2 (binary), 8 (octal), 10 (decimal), or 16 ( hexadecimal) number. If the literal is not suffixed with a radix specifier , the assembler uses the value of the current radix to determine the base of the number. The default radix is 10 (decimal), but the .RADIX directive can be used to specify an alternate radix.

Syntax

Integer-Literal:

Binary-Integer-Literal
Octal-Integer-Literal
Decimal-Integer-Literal
Hexadecimal-Integer-Literal
Binary Integer Literals
Syntax

Binary-Integer-Literal:

Unqualified-Binary-Integer-Literal
Qualified-Binary-Integer-Literal

Unqualified-Binary-Integer-Literal:

Binary-Digit
Binary-Integer-Literal Binary-Digit

Qualified-Binary-Integer-Literal:

Unqualified-Binary-Integer-Literal Binary-Radix

Binary-Digit:

0
1

Binary-Radix:

b
B
y
Y
Description

A base-2 number containing either of the digits 0 and 1.

Examples

The following are examples of unqualified binary integer literals: 

10101
0
000001
1111000010101010

The following are examples of qualified binary integer literals: 

00001111b
1111Y
00y
1111000010101010B
Octal Integer Literals
Syntax

Octal-Integer-Literal:

Unqualified-Octal-Integer-Literal
Qualified-Octal-Integer-Literal

Unqualified-Octal-Integer-Literal:

Octal-Digit
Octal-Integer-Literal Octal-Digit

Qualified-Octal-Integer-Literal:

Unqualified-Octal-Integer-Literal Octal-Radix

Octal-Digit: one of: 

0 1 2 3 4 5 6 7

Octal-Radix:

o
O
q
Q
Description

A base-8 number containing any of the digits 0 through 7.

Examples

The following are examples of unqualified octal integer literals: 

01234567
27
765

The following are examples of qualified octal integer literals: 

27q
013o
567O
01234567Q
Decimal Integer Literals
Syntax

Decimal-Integer-Literal:

Unqualified-Decimal-Integer-Literal
Qualified-Decimal-Integer-Literal

Unqualified-Decimal-Integer-Literal:

Decimal-Digit
Decimal-Integer-Literal Decimal-Digit

Qualified-Decimal-Integer-Literal:

Unqualified-Decimal-Integer-Literal Decimal-Radix

Decimal-Digit: one of: 

0 1 2 3 4 5 6 7 8 9

Decimal-Radix:

d
D
t
T
Description

A base-10 number containing any of the digits 0 through 9.

Examples

The following are examples of unqualified decimal integer literals: 

0123456789
19
090

The following are examples of qualified decimal integer literals: 

01d
89t
4567D
0123456789T
Hexadecimal Integer Literals
Syntax

Hexadecimal-Integer-Literal:

Unqualified-Hexadecimal-Integer-Literal
Qualified-Hexadecimal-Integer-Literal

Unqualified-Hexadecimal-Integer-Literal:

Decimal-Digit
Hexadecimal-Integer-Literal Decimal-Digit
Hexadecimal-Integer-Literal Hexadecimal-Digit

Qualified-Hexadecimal-Integer-Literal:

Unqualified-Hexadecimal-Integer-Literal Hexadecimal-Radix

Decimal-Digit: one of: 

0 1 2 3 4 5 6 7 8 9

Hexadecimal-Digit: one of: 

a b c d e f
A B C D E F

Hexadecimal-Radix:

h
H
Description

A base-16 number using any combination of the digits 0 through 9 and the lowercase letters a through f or the uppercase letters A through F. The lowercase and uppercase representations of any given hexadecimal letter are equivalent.

Constraints

A hexadecimal integer literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the 0 digit.

Examples

The following are examples of unqualified hexadecimal integer literals: 

01BD
9A
0AB

The following are examples of qualified hexadecimal integer literals: 

1234ABCDh
01DH
0bh
1111FFFFH

Floating-Point Literals

Description

A floating-point literal is a notation for representing real numbers. The assembler provides both decimal and hexadecimal floating-point notations for representing real numbers.

Syntax

Floating-Point-Literal:

Decimal-Floating-Point-Literal
Hexadecimal-Floating-Point-Literal
Decimal Floating-Point Literals
Syntax

Decimal-Floating-Point-Literal:
Significand-Part
Significand-Part Exponent-Part

Significand-Part:
Digit-Sequence.Digit-Sequence
Digit-Sequence.

Exponent-Part:
E-Character Digit-Sequence
E-Character Sign Digit-Sequence

E-Character:
e
E

Sign:
-
+

Digit-Sequence:
Digit
Digit-Sequence Digit

Digit:one of:
0 1 2 3 4 5 6 7 8 9

Description

A decimal floating-point literal has a significand part that may be followed by an exponent part. The significand part consists of a digit sequence representing the whole-number part, followed by a period (.), followed by a digit sequence representing the fraction part. The exponent part consists of an introductory character (eor E), followed by an optional sign character (+or -), followed by a digit sequence representing the exponent.

Constraints

The introductory Digit-Sequence in the Significand-Part must be specified ( the literal cannot begin with a ".").

Examples
25.23 
2.523E1 
2523.0E-2
Hexadecimal Floating-Point Literals
Syntax

Hexadecimal-Floating-Point-Literal:
Hexadecimal-Literal Float-Radix

Hexadecimal-Literal:
Decimal-Digit
Hexadecimal-Literal Decimal-Digit
Hexadecimal-Literal Hexadecimal-Digit

Decimal-Digit:one of:
0 1 2 3 4 5 6 7 8 9

Hexadecimal-Digit:one of:
a b c d e f
A B C D E F

Float-Radix:
r
R

Description

A hexadecimal floating-point literal provides a means of initializing floating point values using a notation more closely tied to the internal machine representation than that of the Decimal-Floating-Point-Literal. Such literals are coded in a fashion similar to that of a normal Hexadecimal-Integer-Literal, but a different radix suffix is used to inform the assembler that the value is to be used in the allocation of real numbers rather than integers.

Constraints

A hexadecimal floating-point literal may not begin with any of the alphabetic hexadecimal characters or it will be interpreted as an identifier; such numbers must be prefixed with the 0 digit.

The literal must specify the correct number of hexadecimal digits according to the size of the real-number data-type to which it will be assigned. For REAL4, REAL8, and REAL10 variables, the respective number of digits in the literal must be 8, 16, and 20. For literals encoded with a leading zero, the respective number of digits must be 9, 17, and 21.

Examples
3F800000r

String Literals

Syntax

String-Literal:
D-String
S-String

D-String:
D-Quote D-Quote
D-Quote D-Char-Sequence D-Quote

S-String:
S-Quote S-Quote
S-Quote S-Char-Sequence S-Quote

D-Char-Sequence:
any printable character except D-Quote
D-Quote D-Quote

S-Char-Sequence:
any printable character except S-Quote
S-Quote S-Quote

D-Quote:
"

S-Quote:

Description

A string literal contains a sequence of zero or more characters enclosed in quotation mark symbols. Either a single (') or double (") quotation mark symbol may be used as the quote character that opens and closes the string literal. If a single quotation mark symbol is used as the quote character, then double quotation mark symbols may appear as data characters within the string literal, and vice versa. If the quote character must also appear as a character within the string literal, use two adjacent quote characters; this will allow a single occurrence of the quote character to be inserted into the string literal.

A quote character must be used to terminate the string literal before the end of the line is reached, otherwise an error message is issued and the literal is terminated by the end of line character. A string literal may span multiple lines only if a backslash (\) appears as the last non- whitespace character on the line, in which case the backslash, all surrounding whitespace characters, and the end of line character are deleted and the literal is continued with the first character on the next line.

Examples
'Hello, world'
"That's the way it is"
'Unless its not'
"SuperStringCon \
catenated"

Punctuators

Description

Punctuators are used as operators and separator characters.

Syntax

Punctuator:one of
[ ] ( ) { } * , : = ; %

Declarations

A Type Declaration is a language construct that specifies the characteristics of code and data objects used in a program.

Type Declarations

Description

A Type-Declaration is a common construct used in various assembler directives to establish type attribute information for a program object. A Type-Declaration is needed to determine the data type of a variable or labeled address. The TYPEDEF directive offers a method of assigning a name to a Type-Declaration.

Syntax

Type-Declaration:

TypeName
TypeName Array-Spec
Pointer-Spec
Pointer-Spec TypeName
Pointer-Spec TypeName Array-Spec

Pointer-Spec:

PTR
Distance-TypeName PTR
Pointer-Spec Array-Spec

Array-Spec:

[ Expression ]
Array-Spec [ Expression ]

TypeName:

Distance-TypeName
Scalar-TypeName
UserDefined-TypeName
Examples

The TYPEDEF directive is used to illustrate the type declaration syntax: 

CHAR        typedef   byte               ;   Alias of intrinsic TypeName
PBYTE       typedef   ptr  byte          ;   Pointer to intrinsic TypeName
PCHAR       typedef   ptr  CHAR          ;   Pointer to TypeDef-TypeName
PPCHAR      typedef   ptr  PCHAR         ;   Pointer to a pointer to a CHAR
PPBYTE      typedef   ptr  ptr byte      ;   Similar to PPCHAR
PVOID       typedef   ptr                ;   Pointer to nothing (pointer to code)
PCODE       typedef   ptr  PROC          ;   Similar to PVOID
PFCODE      typedef   far  ptr far       ;   Far pointer to far code address

; vector declarations

ACHAR       typedef   CHAR[16]          ;   Array of 16 characters
AAWORD      typedef   word[2][2]        ;   multi-dimensional array
APBYTE      typedef   ptr[8] byte       ;   Array of 8 pointers to byte
APACHAR     typedef   ptr[4] ACHAR      ;   Array of 4 ptrs to arrays of 16 chars

SIZES_T     struct                     ;   define an intrinsic structure type
   little   byte      ?
   Medium   word      ? 
   BIG      dword     ? 
SIZES_T     ends 

SIZES       typedef   SIZES_T           ;   alias for intrinsic structure type
PSIZES      typedef   ptr SIZES_T       ;   and a type to point to it

PFORWARD    typedef   ptr FORWARD       ;   Pointers to forward-referenced types
FORWARD     struct                     ;   are assumed to be pointers to structs
   blah      word     ?
FORWARD     ends

Expressions

An expression is a sequence of operators and operands that are evaluated to derive a numeric result, an effective address, or a register operand.

Expressions are specified using standard infix notation, which is recursive in nature, ie., expressions may be nested within other expressions. The evaluation of an expression occurs in a left to right manner, and is influenced by the rules of operator precedence and associativity. The order in which expressions are evaluated can be controlled by grouping operands and operators together using parentheses ().

Expression Syntax

Description

This section describes the complete expression syntax.

Syntax

Expression:

Duplicative-Expression

Duplicative-Expression:

Attribute-Expression
Attribute-Expression DUP ( Initializer-List )

Attribute-Expression:

OR-Expression SHORT Additive-Expression
.TYPE OR-Expression
OPATTR OR-Expression

OR-Expression:

AND-Expression
OR-Expression OR AND-Expression
OR-Expression XOR AND-Expression

AND-Expression]]:

NOT-Expression]]
AND-Expression]] AND NOT-Expression

NOT-Expression]]:

Relational-Expression NOT Relational-Expression

Relational-Expression:

Additive-Expression
Relational-Expression EQ Additive-Expression
Relational-Expression NE Additive-Expression
Relational-Expression GT Additive-Expression
Relational-Expression GE Additive-Expression
Relational-Expression LT Additive-Expression
Relational-Expression LE Additive-Expression

Additive-Expression:'

Multiplicative-Expression
Additive-Expression + Multiplicative-Expression
Additive-Expression - Multiplicative-Expression

Multiplicative-Expression:

Narrowed-Expression
Multiplicative-Expression * Narrowed-Expression
Multiplicative-Expression / Narrowed-Expression
Multiplicative-Expression MOD Narrowed-Expression
Multiplicative-Expression SHL Narrowed-Expression
Multiplicative-Expression SHR Narrowed-Expression

Narrowed-Expression:

Cast-Expression
HIGH Cast-Expression
HIGHWORD Cast-Expression
LOW Cast-Expression
LOWWORD Cast-Expression

Cast-Expression:

Element-Selection-Expression
OFFSET Cast-Expression
SEG Cast-Expression
THIS Element-Selection-Expression
TYPE Element-Selection-Expression
Cast-Expression PTR Cast-Expression
Cast-Expression : Cast-Expression

Element-Selection-Expression:

Sign-Expression
Element-Selection-Expression
Sign-Expression
Element-Selection-Expression . Sign-Expression

Sign-Expression:

Primary-Expression
- Primary-Expression
+ Primary-Expression

Primary-Expression:

Literal-Operand
Record-Constant
Identifier-Operand
Register-Operand
Integral-TypeName-Operand
Value-Substitution-Operand
LENGTH Identifier-Operand
LENGTHOF Identifier-Operand
MASK Identifier-Operand
SIZE Element-Selection-Expression
SIZEOF Element-Selection-Expression
WIDTH Identifier-Operand
Parenthesized-Expression
Indirected-Expression
Compound-Initializer

Literal-Operand:

Floating-Point-Literal
Integer-Literal
String-Literal]]

Record-Constant:

Identifier-Operand < Field-List >
Identifier-Operand { Field-List }

Field-List:

Attribute-Expression
Field-List , Attribute-Expression

Identifier-Operand:

Identifier

Register-Operand:

Processor-Register

Integral-TypeName-Operand:

Scalar-TypeName
Distance-TypeName

Value-Substitution-Operand:

Anonymous-Label-Alias
Location-Counter-Alias
Indeterminate-Value-Alias
FLAT

Parenthesized-Expression:

( Attribute-Expression )

Indirected-Expression:

[ Attribute-Expression ]

Compound-Initializer:

< Initializer-List >
{ Initializer-List }

Initializer-List:

Duplicative-Expression
Initializer-List , Duplicative-Expression

Duplicative Initialization Expression

Description

A Duplicative Initialization Expression is one that can be optionally used during the initialization of variables such that the operand is duplicated a specified number of times.

Syntax

Duplicative-Expression:

Attribute-Expression
Attribute-Expression
#DUP ( Initializer-List )

Initializer-List:

Duplicative-Expression
Initializer-List , Duplicative-Expression
Duplicative Initialization (DUP Operator)
Description

The DUP operator creates a Duplicated-ExpressionType from the Initializer-List enclosed in parentheses. This construct can be used to create arrays of information during data allocation.

Syntax

Attribute-Expression DUP (Initializer-List) Initializer-List: Duplicative-Expression Initializer-List,|Duplicative-Expression

Constraints

The left hand operand of the DUP operator must evaluate to an Absolute-ExpressionType.

Each Duplicative-Expression in the Initializer-List must evaluate to an Initializer-ExpressionType.

Examples
STR   STRUCT 
 One   BYTE  0
 Two   BYTE  0
STR   ENDS 

Array1  WORD 4 DUP (1,2,3,4)         ; allocates 16 words
Array2  STR  8 DUP (<1,2>)           ; 8 structures

Attribute Expression

Description

An Attribute Expression is one that optionally extracts or modifies one or more of the basic properties of its operand.

Syntax

Attribute-Expression:

OR-Expression
SHORT Additive-Expression
.TYPE OR-Expression
OPATTR OR-Expression
Expression Descriptor Bitmap (.TYPE Operator)
Description

The .TYPE operator is considered obsolete. The #OPATTR operator should be used instead.

The .TYPE operator returns a byte value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table:

7 6 5 4 3 2 1 0 BIT SET IF EXPRESSION
1 Is a Direct-ExpressionType
1 Is a Indirect-ExpressionType, an Indexed-ExpressionType, or a combination of both
1 Is an Immediate-ExpressionType
1 Is an Indirect-ExpressionType
1 Is a Register-ExpressionType
1 Was parsed and evaluated without error (no undefined symbols, etc.)
1 Is relative to the SS Segment-Register
1 Contains an External Reference

.TYPE OR-Expression

Syntax

.TYPE OR-Expression

Examples
BumpCounter macro bump 
  if (((.TYPE (bump)) and 07h) eq 04h)
     Counter = Counter + bump
  else
     .err <Non-constant value passed to BumpCounter>
  endif
endm
Extended Descriptor Bitmap (OPATTR Operator)

OPATTR OR-Expression

Syntax

OPATTR OR-Expression'

Description

The OPATTR operator returns a superset of the information returned by the .TYPE operator, which should be considered obsolete.

The OPATTR operator returns a word value bitmap that describes various attributes of its operand. The return value is 0 if the expression could not be correctly parsed or evaluated, otherwise the bitmap returned is formatted according to the following table:

A98 7 6 5 4 3 2 1 0 BIT SET IF EXPRESSION
1 Is a Direct-ExpressionType
1 Is a Indirect-ExpressionType, an Indexed-ExpressionType, or a combination of both
1 Is an Immediate-ExpressionType
1 Is an Indirect-ExpressionType
1 Is a Register-ExpressionType
1 Was parsed and evaluated without error (no undefined symbols, etc.)
1 Is relative to the SS Segment-Register
1 Contains an External Reference
LLL Language encoding (described below)

The LLL field (bits 8, 9, and A) comprise an enumerated value that describes the language attribute assigned to the expression as follows:

  • 000 No language attribute used in expression
  • 001 C
  • 010 SYSCALL
  • 011 STDCALL
  • 100 PASCAL
  • 101 FORTRAN
  • 110 BASIC
  • 111 OPTLINK
Constraints

This operator is not available in M510 mode.

Examples
L_MASK     equ 011100000000y               ; mask to isolate language bits
L_OPTLINK  equ 011100000000y               ; setting for OptLink calling convention
VerifyCallBack   macro   ProcName 
  if (((OPATTR (ProcName)) and L_MASK) ne L_OPTLINK)
     .err <Call-back routine must have OptLink linkage>
  endif
endm
Force Short Relative Address (SHORT Operator)
Syntax

SHORT Additive-Expression

Description

The SHORT operator forces the assembler to calculate the distance from the start of the next instruction to the target specified by the operand (given by Additive-Expression) to be less than 128 bytes away. This can cause the assembler to generate more efficient control transfer instructions when the target is a forward reference. By default, the assembler assumes that the code-relative target is of NEAR distance when the target is an unqualified forward reference.

Constraints

The Additive-Expression must evaluate to a Direct-ExpressionType.

Examples
  JMP     Forward                ; target unknown, NEAR jump generated
  JMP     SHORT Forward          ; force SHORT encoding
  .
  .                      ; fewer than 128 bytes of instructions
  .
Forward:                 ; definition of target

Bitwise OR Expression

Description

A Bitwise OR Expression is one where an optional binary bitwise OR operation between the left and right operands is performed and the result returned.

Syntax

OR-Expression: AND-Expression OR-Expression OR AND-Expression OR-Expression XOR AND-Expression

Bitwise Inclusive OR (OR Operator)
Syntax

OR-Expression OR AND-Expression

Description

The OR operator performs a binary bitwise OR operation on the left and right hand operands.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
One  EQU  1
Two  EQU  2

MOV  AX, One OR Two        ; moves 3 into AX
Bitwise Exclusive OR (XOR Operator)
Syntax

OR-Expression XOR AND-Expression

Description

The XOR operator performs a binary bitwise XOR operation on the left and right hand operands.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
Lower  EQU  0101y          ; 7h - binary radix suffix
Upper  EQU  1100y          ; Eh - binary radix suffix

MOV  AX, Upper XOR Lower   ; moves 1001 into AX

Bitwise AND Expression

Description

A Bitwise AND Expression is one where an optional binary bitwise AND operation between the left and right operands is performed and the result returned.

Syntax

AND-Expression:

NOT-Expression
AND-Expression AND NOT-Expression
Bitwise AND (AND Operator)
Syntax

AND-Expression AND NOT-Expression

Description

The AND operator performs a binary bitwise AND operation on the left and right hand operands.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
Lower  EQU  0111y           ; 7h - binary radix suffix
Upper  EQU  1110y           ; Eh - binary radix suffix

MOV  AX, Upper XOR Lower    ; moves 0110 into AX

Bitwise One's Complement Expression

Description

A Bitwise One's Complement Expression is one that performs an optional unary bitwise negation of its operand and returns the result.

Syntax

NOT-Expression: Relational-Expression NOT Relational-Expression

Bitwise One's Complement (NOT Operator)
Syntax

NOT Relational-Expression

Description

The NOT operator performs a unary bitwise negation on its operand.

Constraints

The operand must evaluate to a Constant-ExpressionType.

Examples
  Value  EQU 0111y          ; 7h - binary radix suffix

  MOV    EAX, NOT Value     ; moves FFFFFFF8 into EAX

Relational Expression

Description

A Relational Expression is one where an optional binary comparision operation between the left and right operands is performed and the result returned.

Syntax
Relational-Expression:
Additive-Expression
Relational-Expression EQ Additive-Expression
Relational-Expression NE Additive-Expression
Relational-Expression GT Additive-Expression
Relational-Expression GE Additive-Expression
Relational-Expression LT Additive-Expression
Relational-Expression LE Additive-Expression
Equal To (EQ Operator)
Syntax
Relational-Expression EQ Additive-Expression
Description

The EQ operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are equal, and false (all bits off) if they are not equal.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
  IF 1234 EQ 5678
    TRUE = 1
  ELSE
    TRUE = 0                ; Sets TRUE to 0
  ENDIF
Not Equal To (NE Operator)
Syntax
Relational-Expression NE Additive-Expression
Description

The NE operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if they are not equal, and false (all bits off) if they are equal.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
IF 1234 NE 5678
    TRUE = 1                ; Sets TRUE to 1
ELSE
    TRUE = 0
ENDIF
Greater Than (GT Operator)
Syntax
Relational-Expression GT Additive-Expression
Description

The GT operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than the right operand, and false (all bits off) if it is not.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
IF 1234 GT 5678 
  TRUE = 1 
ELSE 
  TRUE = 0              ; Sets TRUE to 0
ENDIF
Greater Than or Equal To (GE Operator)
Syntax
Relational-Expression GE Additive-Expression
Description

The GE operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is greater than or equal to the right operand, and false (all bits off) if it is not.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
IF 1234 GE 1234 
    TRUE = 1                ; Sets TRUE to 1
ELSE 
    TRUE = 0 
ENDIF
Less Than (LT Operator)
Syntax
Relational-Expression LT Additive-Expression
Description

The LT operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than the right operand, and false (all bits off) if it is not.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
  IF 1234 LT 5678
      TRUE = 1               ; Sets TRUE to 1
  ELSE
      TRUE = 0
  ENDIF
Less Than or Equal To (LE Operator)
Syntax
Relational-Expression LE Additive-Expression
Description

The LE operator performs a binary logical comparision on the left and right hand operands. It returns true (all bits on) if the left operand is less than or equal to the right operand, and false (all bits off) if it is not.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
  IF 1234 LE 1234
    TRUE = 1                  ; Sets TRUE to 1
  ELSE 
    TRUE = 0
  ENDIF

Additive Expression

Description

A Additive Expression is one where an optional binary additive arithmetic operation between the left and right operands is performed and the result returned.

Syntax
Additive-Expression:
Multiplicative-Expression
Additive-Expression + Multiplicative-Expression
Additive-Expression - Multiplicative-Expression
Addition (+ Operator)
Syntax
Additive-Expression + Multiplicative-Expression
Description

The + operator performs a binary addition operation on the left and right hand operands, and returns the result.

Constraints

One of the operands must evaluate to a Constant-ExpressionType. If one of the operands references an external identifier, then the other operand must be a Constant-ExpressionType without an external reference. Both operands must be of scalar type.

Examples
 VALUE = 100 + 11          ; sets VALUE to 111
Subtraction (- Operator)
Syntax
Additive-Expression - Multiplicative-Expression
Description

The - operator performs a binary subtraction operation on the left and right hand operands, and returns the result.

Constraints

The right operand must evaluate to a Constant-ExpressionType and reference no external identifiers. If both operands are relocatable, they must reside within the same segment, in which case the result is converted to a Absolute-ExpressionType. Both operands must be of scalar type.

Examples
 VALUE = 111 - 11           ; sets VALUE to 100

Multiplicative Expression

Description

A Multiplicative Expression is one where an optional binary multiplicative arithmetic operation between the left and right operands is performed and the result returned.

Syntax
Multiplicative-Expression:
Narrowed-Expression
Multiplicative-Expression * Narrowed-Expression
Multiplicative-Expression / Narrowed-Expression
Multiplicative-Expression MOD Narrowed-Expression
Multiplicative-Expression SHL Narrowed-Expression
Multiplicative-Expression SHR Narrowed-Expression
Multiplication (* Operator)
Syntax
Multiplicative-Expression * Narrowed-Expression
Description

The * operator performs a binary multiplication operation on the left and right hand operands, and returns the result.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
 VALUE = 9 * 3                 ; sets VALUE to 27
Division (/ Operator)
Syntax
Multiplicative-Expression / Narrowed-Expression
Description

The / operator performs a binary division operation on the left and right hand operands, and returns the result.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
 VALUE = 27 / 9                ; sets VALUE to 3
Remainder (MOD Operator)
Syntax
Multiplicative-Expression MOD Narrowed-Expression
Description

The MOD operator performs a binary modulus division operation on the left and right hand operands, and returns the remainder as the result.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
 VALUE = 18 MOD 4              ; sets VALUE to 2
Bitwise Left Shift (SHL Operator)
Syntax
Multiplicative-Expression SHL Narrowed-Expression
Description

The SHL operator shifts the bits in the left hand operand to the left by the number of bits specified in the right hand operand, and returns the result.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
 VALUE = 1111y SHL 4          ; sets VALUE to 11110000y
Bitwise Right Shift (SHR Operator)
Syntax
Multiplicative-Expression SHR Narrowed-Expression
Description

The SHR operator shifts the bits in the left hand operand to the right by the number of bits specified in the right hand operand, and returns the result.

Constraints

Each operand must evaluate to a Constant-ExpressionType.

Examples
 VALUE = 11110000y SHR 4      ; sets VALUE to 00001111y

Narrowed Expression

Description

A Narrowed Expression is one that performs an optional unary narrowing operation on its operand and returns the result.

Syntax

Narrowed-Expression:

Cast-Expression HIGH Cast-Expression
HIGHWORD Cast-Expression
LOW Cast-Expression
LOWWORD Cast-Expression
Upper 8 Bits of WORD Expression (HIGH Operator)
Syntax
HIGH Cast-Expression
Description

The HIGH operator returns the upper 8 bits of a 16-bit expression. Only bits 8-15 are returned, even if the magnitude of the operand exceeds 16 bits.

Constraints

The operand must evaluate to a Constant-ExpressionType.

Examples
 FIRST  = 1234h
 SECOND = HIGH FIRST        ; Sets SECOND to 12h
Upper 16 Bits of DWORD Expression (HIGHWORD Operator)
Syntax
HIGHWORD Cast-Expression
Description

The HIGHWORD operator returns the upper 16 bits of a 32-bit expression. Only bits 16-31 are returned, even if the magnitude of the operand exceeds 32 bits.

Constraints

The operand must evaluate to a Constant-ExpressionType.

This operator is not available in M510 mode.

Examples
 FIRST  = 12345678h 
 SECOND = HIGHWORD FIRST    ; Sets SECOND to 1234h
Lower 8 Bits of WORD Expression (LOW Operator)
Syntax
LOW Cast-Expression
Description

The LOW operator returns the lower 8 bits of its operand.

Constraints

The operand must evaluate to a Constant-ExpressionType.

Examples
 FIRST  = 1234h
 SECOND = LOW FIRST         ; Sets SECOND to 34h
Lower 16 Bits of DWORD Expression (LOWWORD Operator)
Syntax
LOWWORD Cast-Expression
Description

The LOWWORD operator returns the lower 16 bits of its operand.

Constraints

The operand must evaluate to a Constant-ExpressionType.

This operator is not available in #M510 mode.

Examples
 FIRST  = 12345678h
 SECOND = LOWWORD FIRST     ; Sets SECOND to 5678h

Type Conversion Expression

Description

A Type Conversion Expression is one that performs an optional type conversion operation on its operand and returns the result.

Syntax

Cast-Expression:

Element-Selection-Expression
OFFSET Cast-Expression
SEG Cast-Expression
THIS Element-Selection-Expression
TYPE Element-Selection-Expression
Cast-Expression PTR Cast-Expression
Cast-Expression : Cast-Expression
Address Offset (OFFSET Operator)
Description

The OFFSET operator returns the offset portion of its operand. For relocatable values, this is the offset into the segment or group to which the expression is relative.

Syntax

OFFSET Cast-Expression

Constraints

The operand may evaluate to any one of the following #ExpressionTypes:

  • Absolute-ExpressionType
  • Constant-ExpressionType
  • Immediate-ExpressionType
  • Direct-ExpressionType
  • Indirect-ExpressionType
Examples
CodeLabel:
       MOV   AX, CodeLabel            ; illegal, no data at address 
       MOV   AX, OFFSET   CodeLabel   ; we want the address itself
Address Segment (SEG Operator)
Syntax

SEG Cast-Expression

Description

The SEG operator returns the segment or group to which a relocatable expression is relative.

Constraints

The operand must evaluate to one of the following ExpressionTypes:

  • Immediate-ExpressionType
  • Direct-ExpressionType
  • Indirect-ExpressionType
  • Indexed-ExpressionType
Examples
DATA    SEGMENT 
Stuff   DB    ? 
        MOV   AX, SEG Stuff    ; This construct is
        MOV   AX, DATA         ; equivalent to this
DATA    ENDS
Address Alias (THIS Operator)
Syntax

THIS Element-Selection-Expression

Description

The THIS operator returns an operand whose:

  • Relative Frame attribute is set to that of the current segment
  • Displacement attribute is set to the current location counter
  • Type Declaration attribute is set to that of the expression given by the Element-Selection-Expression operand.
Constraints

The operand must evaluate to a Type-ExpressionType.

Examples
DATA      SEGMENT

ALIAS   EQU   THIS BYTE        ; reference this address as a byte
Stuff   DB    ? 
        MOV   AL, ALIAS        ; This construct is
        MOV   AL, Stuff        ; equivalent to this
DATA    ENDS
Datatype Extraction (TYPE Operator)
Syntax

TYPE Element-Selection-Expression

Description

The TYPE operator returns the Type-ExpressionType attribute of its operand.

Constraints

None

Examples
CODE    SEGMENT 
        ASSUME  CS:CODE, DS:CODE
Stuff   DB      ?                        ; TYPE Stuff is BYTE
        MOV     [BX],(TYPE Stuff) PTR 1  ; stores 1 as a BYTE at [BX]
CODE    ENDS
Type Conversion (PTR Operator)
Syntax

Cast-Expression PTR Cast-Expression

Description

The PTRoperator converts the right operand to the type specified by the left operand.

Constraints

The left operand must be a Type-ExpressionType.

Examples
CODE     SEGMENT 
         MOV  BYTE PTR [BX], 1    ; stores 1 as a BYTE at [BX]
CODE     ENDS
Segment Override (: Operator)
Syntax

Cast-Expression : Cast-Expression

Description

The : (colon) operator forces the right operand to have the Relative Frame attribute of the left operand.

Constraints

The left operand must evaluate to one of the following #ExpressionTypes:

  • Register-ExpressionType where the Register Value attribute is that of a Segment-Register
  • Immediate-ExpressionType where the Relative Frame attribute is that of a GroupName or SegmentName.
Examples
DATA       SEGMENT
Variable   DW    ?
DATA       ENDS

DGROUP     GROUP DATA, CODE

CODE       SEGMENT
  ASSUME   CS:CODE, DS:DGROUP
  MOV      AX, DGROUP:Variable         ; insure Variable is relative to DGROUP
  ASSUME   DS:NOTHING
  MOV      BX, CS:Variable             ; access Variable through CS register
CODE       ENDS

Element Selection Expression

Description

A Element Selection Expression is one that optionally selects a specific element of its operand and returns a reference to it.

Syntax

Element-Selection-Expression:

Sign-Expression]]
Element-Selection-Expression [Sign-Expression]
Element-Selection-Expression .Sign-Expression
Subscript ([] Operator)
Syntax

Element-Selection-Expression [ Sign-Expression ]

Description

The [] binary operator performs a subscripting (or indexing) operation between the operand to the left of the brackets and the operand enclosed within the brackets. This is a simple additive operation of BYTE granularity; the arithmetic performed is not influenced by the Operand Size of either operand.

The syntax for this operator describes a binary operation between the left hand expression and the bracketed expression. The bracketed expression is also subject to the same operations performed during the processing of a standalone Indirected-Expression as described in the section on Primary-Expressions.

Constraints

Only one of the operands may specify a relocatable value.

Examples
CODE    SEGMENT 
        ASSUME  CS:CODE, DS:CODE

Value    DB    0                         ;   Value [0]
         DB    1                         ;   Value [1]
         DB    2                         ;   Value [2]
         DB    3                         ;   Value [3]
         DB    4                         ;   Value [4] 

  MOV      AL, Value [3]        ;   load AL with the fourth byte at Value (3)
  MOV      BX, offset Value     ;   get address of Value 
  MOV      AL, [BX] [1] [2]     ;   also gets the fourth byte ( 3 ) 

CODE     ENDS
Structure/Union Field Selection (. Operator)
Syntax

Element-Selection-Expression . Sign-Expression

Description

The . (period) operator selects a structure or union field entry. It adds the left and right hand operands together and returns the result. The left operand should be an Indirect-ExpressionType, Indexed-ExpressionType, or Type-ExpressionType whose Type Declaration attribute resolves to that of a Structure-TypeName or Union-TypeName. The right operand should refer to a FieldName defined within the referenced type.

The Operand Size attribute of the result depends on the operands involved. If both operands have an operand size, a Structure-FieldName appearing as the right hand operand would override the operand size of the left operand and would dictate the operand size of the resulting expression.

Constraints

Only one of the operands may specify a relocatable value.

Examples
Number   STRUC
  One    DB   1
  Two    DW   2
Number   ENDS

; The following line is only allowed in MASM 5.10 mode ( OPTION OLDSTRUCTS ) 

  MOV   AX,[BX] .Two         ;  BX points to a "Number", get the "Two" entry 

; In other modes, "Two" is private to the "Number" structure type, so 
; one of the following methods are required : 

  MOV   AX,(Number PTR[BX]).Two  ; Explicit override
  MOV   AX,[BX] + Number.Two     ; Fully qualified reference
  ASSUME BX:Number               ; Associate BX with "Number"
  MOV   AX,[BX].Two              ; then original syntax is allowed

Unary Arithmetic Expression

Description

A Unary Arithmetic Expression is one that optionally alters the sign of its operand and returns the result.

Syntax

Sign-Expression:

Primary-Expression
-Primary-Expression
+Primary-Expression
Unary Minus (- Operator)
Syntax

- Primary-Expression

Description

The - operator makes its operand into a negative number and returns the result.

Constraints

The operand must evaluate to a Constant-ExpressionType.

Examples
Value  EQU  1

MOV  AX, -Value     ; move -1 into AX
Unary Plus (+ Operator)
Syntax

+ Primary-Expression

Description

The + operator returns its operand.

Constraints

The operand must evaluate to a Constant-ExpressionType.

Examples
Value EQU 1 
MOV   AX,+Value  ; move 1 into AX

Primary Expression

Description

A Primary Expression is one that returns an expression operand.

Syntax

Primary-Expression:

Literal-Operand
Record-Constant
Identifier-Operand
Register-Operand
Integral-TypeName-Operand
Value-Substitution-Operand
LENGTH Identifier-Operand
LENGTHOF Identifier-Operand
MASK Identifier-Operand
SIZE Element-Selection-Expression
SIZEOF Element-Selection-Expression
WIDTH Identifier-Operand
Parenthesized-Expression
Indirected-Expression
Compound-Initializer
Literal Operand
Syntax

Literal-Operand:

Floating-Point-Literal
Integer-Literal
String-Literal
Description

The assembler accepts several types of literal values as operands within expressions. Literal-Operands are converted to #ExpressionTypes according to the following table:

Floating-Point-Literal Floating-Point-ExpressionType
Integer-Literal Absolute-ExpressionType
String-Literal Absolute-ExpressionType if the string length is less than or equal to the current Address Size; a String-ExpressionType otherwise.

The context where the expression is used determines whether or not a particular type of literal is legal.

Constraints

Arithmetic operations cannot be performed on #Floating-Point-Literals, thus they cannot be the operand of a unary or binary operator.

Value Substitution Operand
Syntax

Value-Substitution-Operand:

Anonymous-Label-Alias
Location-Counter-Alias
Indeterminate-Value-Alias
FLAT
Description

These operands are used to retrieve specialized values that are calculated internally by the assembler.

The FLAT operator returns an expression whose #Relative Frame is set to that of the predefined FLAT pseudo-group.

Constraints

The FLAT operand is only active when a 32-bit processor has been selected.

Record Constant Operand
Syntax

Record-Constant:

Identifier-Operand < Field-List >
Identifier-Operand { Field-List }

Field-List:

Attribute-Expression
Field-List , Attribute-Expression
Description

A Record-Constant provides a method of calculating a single numeric result value from a list of Record-FieldName values, and combining them together according to the definition of the Record-TypeName given by the Identifier-Operand. The result value is a Constant-ExpressionType suitable for use as an instruction operand, or for assigning to a record variable.

The Record-TypeName given by the Identifier-operand determines how the Field-List will be evaluated. The Attribute-Expression entries are position-dependent, and are matched with the corresponding Record-FieldName entries from the Record-TypeName definition to determine their width and shift values. Attribute-Expression entries may be omitted, in which case the default values from the record definition are used in the calculation.

Constraints

The Identifier-Operand must resolve to a Record-TypeName.

Examples
 DATE_T   record   Year  : 7 = 0,   ; 0 is 1980
                   Month : 4 = 1,   ; January
                   Day   : 5 = 1    ; 1st
 
 CODE SEGMENT
   mov  AX,DATE_T  < >                       ; January 1st, 1980
   mov  AX,DATE_T  < 1996 - 1980, 12, 25 >   ; Christmas, 1996
   mov  AX,DATE_T  < 10h, 0Ch, 19h >         ; equivalent values in hex
   mov  AX,DATE_T  < 10000y, 1100y, 11001y > ; equivalent values in binary
   mov  AX,2199h                             ; equivalent value manually coded
   mov  AX,0010000110011001y                 ; and in binary
 ;         YYYYYYYMMMMDDDDD
 CODE   ENDS
Register Operand
Syntax

Register-Operand:

Processor-Register
Description

Processor registers are valid expression operands. The context where the expression is used determines the allowable register operands.

Constraints

The currently selected processor dictates whether or not a register is visible to the expression evaluator.

Identifier Operand
Syntax

Identifier-Operand:

Identifier
Description

When an Identifier is used in an expression, it returns a value according to its Identifier-Type, as shown in the following table:

Identifier-Type VALUE RETURNED
Numeric-EquateName The value originally assigned to the equate.
Structure-FieldName The offset in bytes from the beginning of the structure.
Union-FieldName The offset in bytes from the beginning of the union (always 0).
Record-FieldName The shift-count required to reach the field within the record.
Record-TypeName The mask-value that isolates defined record fields from undefined fields.
Structure-TypeName Zero if mode is M510, otherwise the size of the structure in bytes (the operand size of the structure type).
Union-TypeName The size of the union in bytes (the operand size of the union type).
Typedef-TypeName The operand size of the underlying data-type represented by the Typedef-TypeName.
GroupName A Relative Frame attribute that represents the group, and a Displacement value of zero.
SegmentName A Relative Frame attribute that represents the segment (or the group to which it belongs), and a Displacement value of zero if the mode is M510, or the current segment offset otherwise.
LabelName The Relative Frame attribute where the label is defined, and the segment offset value of the label.
Constraints

The Identifier must resolve to one of the following Identifier-Types:

  • Numeric-EquateName
  • FieldName
  • GroupName
  • LabelName
  • SegmentName
  • UserDefined-TypeName
Integral Type-Name Operand
Syntax

Integral-TypeName-Operand:

Scalar-TypeName
Distance-TypeName
Description

When an Integral-TypeName-Operandis used in an expression, it is converted to a Type-ExpressionType. If used in a numeric context, the following numeric values are returned:

Integral-TypeName-Operand VALUE RETURNED
Scalar-TypeName The operand-size of the type in bytes.
Distance-TypeName If mode is M510, NEAR returns FFFF, and FAR returns FFFE. Otherwise, NEAR and FAR are resolved and the values returned are: NEAR16=FF02, NEAR32=FF04, FAR16=FF05, FAR32=FF06.
Constraints

The NEAR32 and FAR32 keywords are only valid if a 32-bit processor has been selected.

Number of Data Elements (LENGTH Operator)
Syntax

LENGTH Identifier-Operand

Description

The LENGTH operator returns the number of data elements allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the length of the first element is considered.

Constraints

The operand must evaluate to a Data-LabelName.

Number of Data Elements (LENGTHOF Operator)
Syntax

LENGTHOF Identifier-Operand

Description

The LENGTHOF operator returns the number of data elements allocated to the operand.

Constraints

The operand must evaluate to a Data-LabelName.

This operator is not available in M510 mode.

Examples

<none>

Record or Field Bit-Mask (MASK Operator)
Syntax

MASK Identifier-Operand

Description

The MASK operator returns the bit mask required to isolate a field within a record.

Constraints

The Identifier-Operand must resolve to a Record-TypeName or Record-FieldName; otherwise the result is zero.

Size of Variable in Bytes (SIZE Operator)
Syntax

SIZE Element-Selection-Expression

Description

The SIZE operator returns the number of bytes allocated to the operand. When applied to a variable initialized with a series of comma-separated expressions (elements), only the size of the first element is considered.

Constraints

None

Size of Variable in Bytes (SIZEOF Operator)
Syntax

SIZEOF Element-Selection-Expression

Description

The SIZEOF operator returns the number of bytes allocated to the operand.

Constraints

This operator is not available in M510 mode.

Record or Field Width (WIDTH Operator)
Syntax

WIDTH Identifier-Operand

Description

The WIDTHoperator returns the width of a record or a record field name.

Constraints

The Identifier-Operand must resolve to a Record-TypeName or Record-FieldName; otherwise the result is zero.

Precedence (() Operator)
Syntax

Parenthesized-Expression:

( Attribute-Expression )
Description

Parentheses forces the Attribute-Expression operand to be evaluated at a higher precedence level.

Examples
Value =   2 + 3   * 4     ; Value = 14 
Value = ( 2 + 3 ) * 4     ; Value = 20
Indirection ([] Operator)
Syntax

Indirected-Expression:

[ Attribute-Expression ]
Description

During evaluation of the Attribute-Expression, the [](indirection) operator will convert a Register-ExpressionType to a Indexed-ExpressionType by moving the Register Value attribute to either the Base Register or Index Register attribute field as appropriate for the register(s) referenced in the expression. This operation allows values contained in the processor registers to be used during effective address calculation at application run time.

Constraints

See the Indexed-ExpressionType section for information on registers that are valid for use in this context.

Examples
CODE      SEGMENT 
          ASSUME   CS : CODE ,   DS : CODE 
Value     DW     0 
          MOV    BX , offset   Value        ; load the address of Value into BX
          MOV    [ BX ] , BX                ; store the contents of BX into the
                                            ; memory location addressed by [BX]
CODE       ENDS
Compound Initializer List (<> Operator)
Syntax

Compound-Initializer:

< Initializer-List >
{ Initializer-List }

Initializer-List:

Duplicative-Expression
Initializer-List , Duplicative-Expression
Description

The <> (or {}) operator provides a way of specifying a list of expressions to be used for initializing complex (multi-field) variables such as records or structures.

The <> operator encloses a list of comma-separated expressions; individual expressions are optional, but are also positional with respect to the record or structure fields they are intended to initialize. Commas must therefore be used to maintain field positions if empty expressions are encountered in the list.

The initializer list itself may also be left out entirely for those cases where a variable allocation will use the default initializers provided in the record or structure definition (the <>or {} themselves are still required).

Examples
Numbers   STRUCT
  One     DB     0
  Two     DW     0
  Three   DB     0
  Four    DD     0
Numbers   ENDS

First    Numbers   < >               ;  empty initializer list
Second   Numbers   < 1, 2, 3, 4 >    ;  override all defaults
Third    Numbers   < 1 >             ;  override first entry only
Fourth   Numbers   < 1, , , 4 >      ;  override first and last entries

Expression Evaluation

After an expression is parsed and checked for syntax errors, it is evaluated. During evaluation, all calculations and conversions are performed on the operands according to the operators that are applied to them. The final result is a collection of #Expression-Attributes, to which an ExpressionType is assigned.

Expression Attributes

This section describes the Expression-Attributesthat are associated with an expression after it is evaluated.

Address Size

If an expression refers to an effective address, then it also has an associated #address size. The following #ExpressionTypes normally reference an effective address, and thus have an associated address size:

  • Immediate-ExpressionType
  • Direct-ExpressionType
  • Indirect-ExpressionType
  • Indexed-ExpressionType

The address size can be either 2 (USE16) or 4 (USE32). For an expression that references a label, the address size of the segment where the label is defined determines the address size of the expression.

Operand Size

The Operand Size of an expression can be set explicitly using the #Type Conversion (PTR Operator), or it may be a side-effect inherited from the type of data referenced in the expression. The following table describes the operand sizes that will be assigned when an identifier is referenced in an expression:

REFERENCE OPERAND SIZE
8-Bit-Register 1
16-Bit-Register 2
32-Bit-Register 4
Segment-Register 2
Control-Register 4
Debug-Register 4
Test-Register 4
MMX-Register 8
Floating-Point-Register 10
BYTE 1
SBYTE 1
WORD 2
SWORD 2
DWORD 4
SDWORD 4
REAL4 4
FWORD 6
QWORD 8
REAL8 8
TBYTE 10
REAL10 10
NEAR 2 or 4
NEAR16 2
NEAR32 4
FAR 4 or 6
FAR16 4
FAR32 6
Numeric-EquateName Inherited from equate expression
GroupName 2
SegmentName 2
Code-LabelName SIZE (TYPE Code-LabelName)
Data-LabelName SIZE (TYPE Data-LabelName)
Structure-FieldName SIZE Structure-FieldName
Record-TypeName SIZE Record-TypeName
Structure-TypeName SIZE Structure-TypeName
Union-TypeName SIZE Union-TypeName

The Operand Size is 0 for all other identifier types.

Displacement

The Displacement value in an expression is the final calculated value of all numeric quantities, and must be a scalar value. It may also be a reference to a relocatable address, in which case the expression will also have a Relative Frame and/or an External Reference attribute. A Displacement may be used in the calculation of an effective address, either alone or in combination with a Base Register and/or an Index Register.

Relative Frame

The Relative Frame attribute will be present if the expression contains a direct or indirect reference to any of the following #Identifier-Types:

  • GroupName
  • LabelName
  • SegmentName

The Relative Frame attribute indicates that the expression is relocatable, and specifies the GroupName or SegmentName to which the expression is relative.

External Reference

The External Reference attribute will be present if the expression references any external identifiers.

Register Value

The Register Value attribute specifies the value of the Processor-Register referenced in a Register-ExpressionType.

Base Register

The Base Register attribute specifies the value for the base register used in an Indexed-ExpressionType.

Index Register

The Index Register attribute specifies the value for the index register used in an Indexed-ExpressionType.

Scale Factor

The Scale Factor attribute specifies the scaling value used (if any) in an Indexed-ExpressionType.

Type Declaration

The Type Declaration attribute specifies the type of data referenced in the expression. This is the value extracted from the expression when it is used as the left operand of the #Type Conversion (PTR Operator).

Expression Types

Description

An ExpressionType is assigned to every expression during evaluation. The ExpressionType is used to determine whether or not an expression is legal for the context in which it is used. The type of an expression is influenced primarily by the operands that are used, but the use of expression operators also play an important part in determining the type of an expression.

Definition

ExpressionType:

Absolute-ExpressionType
Constant-ExpressionType
Direct-ExpressionType
Floating-Point-ExpressionType
Immediate-ExpressionType
Indirect-ExpressionType
Indexed-ExpressionType
Register-ExpressionType
String-ExpressionType
Type-ExpressionType
Duplicated-ExpressionType
Compound-ExpressionType
Absolute Expression Type

An Absolute-ExpressionType is an expression that evaluates to an integer quantity. Its value must be representable using one of the following types of scalar data:

  • BYTE
  • SBYTE
  • WORD
  • SWORD
  • DWORD
  • SDWORD
  • FWORD
  • QWORD
  • TBYTE

The following restrictions apply to an Absolute-ExpressionType:

  • It cannot be relocatable (it may not contain references to a GroupName, SegmentName or LabelName).
  • It cannot reference any external symbols.
  • It cannot contain any forward references.
Constant Expression Type

A Constant-ExpressionType is an Absolute-ExpressionType with the following restrictions relaxed:

  • It may contain forward references to identifiers defined later in the source stream.
  • It may reference a single external symbol, provided that the symbol was declared in an EXTERN directive with the ABS attribute.
Immediate Expression Type

An Immediate-ExpressionType has all the properties of a Constant-ExpressionType with the following restrictions relaxed:

  • It may contain references to a GroupName, SegmentName or LabelName(it may be relocatable).
  • It may reference a relocatable external symbol.

An Immediate-ExpressionType must not be larger than 32 bits in magnitude; its value must be representable using one of the following types of scalar data:

  • BYTE
  • SBYTE
  • WORD
  • SWORD
  • DWORD
  • SDWORD
Direct Expression Type

A Direct-ExpressionType is an expression that references a Code-LabelName. It can be used directly in code-relative instructions without conversion. There is no data type associated with the address that a Direct-ExpressionType represents, therefore It may not be used in a data-relative instruction without first being explicitly converted to another expression type.

Indirect Expression Type

An Indirect-ExpressionType is an expression that references a Data-LabelName. It can be used directly in data-relative instructions without conversion to another expression type.

Indexed Expression Type

An Indexed-ExpressionType is an expression that calculates an effective memory address using the contents of a Base-Register, an Index-Register, or both. A Processor-Register must first be converted to a Base-Register or Index-Register by specifying it as the operand of the [[#Indirection ([] Operator)]]before the expression can be converted to an Indexed-ExpressionType.

When calculating a 16-bit effective address, only the BP and BX registers may be used as Base-Registers, and only the DI and SI registers may be used as Index-Registers.

When calculating a 32-bit effective address, only the EAX, EBX, ECX, EDX, EDI, ESI, EBP, and ESP registers may be used as Base-Registers, and only the EAX, EBX, ECX, EDX, EDI, ESI, and EBP registers may be used as Index-Registers.

Note: Only a single Base-Register and a single Index-Register may be used in a given expression.

On 80386 (and higher) processors, the #Multiplication (* Operator) may be used with an Index-Registeroperand and an Absolute-ExpressionType operand to establish a scaling factor that is applied to the Index-Register during effective address calculation. The scaling factor effectively causes the Index-Register to be multiplied by a fixed value at run time. The scaling Expression must evaluate to 1 (no scale factor), 2, 4, or 8.

A Direct-ExpressionType or an Indirect-ExpressionType may be a sub-expression of an Indexed-ExpressionType.

Register Expression Type

A Register-ExpressionType is an expression that specifies a single Processor-Register.

String Expression Type

A String-ExpressionType is an expression that specifies a single String- Literal.

Floating-Point Expression Type

A Floating-Point-ExpressionType is an expression that specifies a single Floating-Point-Literal.

Type Expression Type

A Type-ExpressionTypeis an expression that specifies one of the following:

  • A Scalar-TypeName
  • A Distance-TypeName
  • A UserDefined-TypeName
Compound Expression Type

A Compound-ExpressionType evaluates to a list of (possibly nested) expressions collected together as a unit by the #Compound Initializer List ( <> Operator). A Compound-ExpressionTypeis used to initialize #aggregate data types (such as records, structures, and unions) and #vector data types (arrays).

Duplicated Expression Type

A Duplicated-ExpressionType evaluates to an expression that is to be duplicated (repeated) a specified number of times. This type of expression is created using the #Duplicative Initialization (DUP Operator).

Operand Expression Type

An Operand-ExpressionType consists of those #ExpressionTypes that are valid for use as operands in processor instructions. The following ExpressionTypes are not valid for use as an Operand-ExpressionType:

  • Compound-ExpressionType
  • Duplicated-ExpressionType
  • A String-ExpressionType is only valid as an Operand-ExpressionType if it is short enough to be converted to an Absolute-ExpressionType having an Operand Size less than or equal to the current Address Size setting.

Operand-ExpressionType:

Absolute-ExpressionType
Constant-ExpressionType
Immediate-ExpressionType
Direct-ExpressionType
Indirect-ExpressionType
Indexed-ExpressionType
Register-ExpressionType
String-ExpressionType
Floating-Point-ExpressionType
Type-ExpressionType
Description

An Operand-ExpressionTypeconsists of those #ExpressionTypes that are valid for use as operands in processor instructions. The following ExpressionTypes are not valid for use as an Operand-ExpressionType:

  • Compound-ExpressionType
  • Duplicated-ExpressionType

A String-ExpressionType is only valid as an Operand-ExpressionType if it is short enough to be converted to an Absolute-ExpressionType having an Operand Size less than or equal to the current Address Size setting.

Definition

Operand-ExpressionType:

Absolute-ExpressionType
Constant-ExpressionType
Immediate-ExpressionType
Direct-ExpressionType
Indirect-ExpressionType
Indexed-ExpressionType
Register-ExpressionType
String-ExpressionType
Floating-Point-ExpressionType
Type-ExpressionType

Initializer Expression Type

An Initializer-ExpressionType consists of those #ExpressionTypes that are valid for use in initializing variables. The following ExpressionTypes are not valid Initializer-ExpressionTypes:

  • Indexed-ExpressionType
  • Register-ExpressionType

Initializer-ExpressionType:

Scalar-Initializer-ExpressionType
Compound-ExpressionType
Duplicated-ExpressionType

Scalar-Initializer-ExpressionType:

Absolute-ExpressionType
Constant-ExpressionType
Immediate-ExpressionType
Direct-ExpressionType
Indirect-ExpressionType
String-ExpressionType
Floating-Point-ExpressionType
Type-ExpressionType
Description

An Initializer-ExpressionType consists of those #ExpressionTypes that are valid for use in initializing variables. The following ExpressionTypes are not valid Initializer-ExpressionTypes:

  • Indexed-ExpressionType
  • Register-ExpressionType
Definition

Initializer-ExpressionType:

Scalar-Initializer-ExpressionType
Compound-ExpressionType
Duplicated-ExpressionType

Scalar-Initializer-ExpressionType:

Absolute-ExpressionType
Constant-ExpressionType
Immediate-ExpressionType
Direct-ExpressionType
Indirect-ExpressionType
String-ExpressionType
Floating-Point-ExpressionType
Type-ExpressionType

Text Preprocessor

The text preprocessor is a functional unit within the assembler that performs the text preprocessing translation phase. During text preprocessing, the following actions are performed:

  1. Language Elements are recognized.
  2. Text equates and macros are expanded.
  3. Macro directives and conditional assembly directives are recognized and processed.
  4. The preprocessed output is passed on to the assembler for final processing.

This section also describes the various types of preprocessor directives:

Type Function Directives
Conditional Assembly Tests for a specified condition and assembles a block of statements if the condition is true. IF IFB IFDEF IFDIFI IFE IFIDN IFNB IFNDEF IF1 IF2 ELSE ENDIF
Text Equate Allows assignment of simple text strings to a symbolic name. Provides functions for expanding and operating on the values. CATSTR EQU INSTR SIZESTR SUBSTR
Macro Provides text processing that is done sequentially at assembly time. By the end of assembly, ALP expands all macros and assembles the resulting text into object code. ENDM EXITM FOR FORC IRP IRPC LOCAL MACRO PURGE REPEAT REPT
Miscellaneous Miscellaneous text processing functions. COMMENT ECHO %OUT INCLUDE

Text Operators

Description

The #Text Preprocessor recognizes certain punctuator characters as text operators. The programmer may use these operators to force the Text Preprocessor to perform various operations such as delineating text, expanding arguments, and converting expressions into their text representations.

Syntax

Text-Operator:

Literal-Character-Operator
Literal-Text-Operator
Text-Expansion-Operator
Text-Substitution-Operator

Literal Character Operator (!)

Syntax

Literal-Character-Operator:

! any printable character
Description

When you use an exclamation point (!) in an operand, ALP treats the next character literally. (!) is typically used to prevent the assembler from recognizing and acting upon special characters such as the semicolon (;) or the ampersand (&), forcing them to appear as normal data characters.

Constraints

The Literal-Character-Operator has no effect when used inside of a String-Literal.

Examples

In this example, use of the ! in the second macro argument prevents the assembler from interpreting the rest of the line as a comment: 

MACRONAME   First, !; NonComment, Third              ; Comment

Literal Text Operator (<>)

Syntax

Literal-Text-Operator:

< Char-Sequence >

Char-Sequence

any printable character
Char-Sequence any printable character
Description

The literal-text operator directs the assembler to treat Char-Sequence as a single literal element regardless of whether it contains commas, spaces, or other separators. The operator is most often used with macro calls and the FOR directive to ensure that values in a parameter list are treated as a single parameter.

The literal-text operator can also be used to force ALP to treat other special characters such as the semicolon (;) or the ampersand (&) literally. For example, the semicolon inside angle brackets (<>) becomes a semicolon, not a comment indicator.

ALP removes one set of angle brackets each time the parameter is used in a macro. When using nested macros, you will need to supply as many sets of angle brackets as there are levels of nesting. The assembler recognizes nested occurrences of text literals.

Examples

The following example illustrates how to pass arbitrary text to a macro as a single parameter: 

MACRONAME   First, <Second Argument>, <Third, <Nested>, Argument>

The macro will receive three separate arguments:

  1. First
  2. Second Argument
  3. Third, <Nested>, Argument

Notice that the outermost set of angle brackets were removed from the second and third arguments.

Text Expansion Operator (%)

Syntax

Text-Expansion-Operator:

% 2nd through Nth token on line
% Text-EquateName
% Expression
Description

The % Text-Expansion-Operator has different effects depending upon the context in which it is used. Its primary purpose is convert various sources of information into text literals that may in turn be passed to macros as arguments.

The % Text-Expansion-Operator causes the following types of conversions:

Line Expansion

When used as the first token on the line, the % operator forces expansion of Text-EquateNames in contexts where they would otherwise be left unexpanded. Text-EquateNames passed as arguments to macros are not automatically expanded; this is one context where the % operator is useful.

Expansion of a Text Equate Operand

As with Line Expansion, the % operator may be used within the body of a line to expand individual Text-EquateNames. This can be useful when expansion of all Text-EquateNames on the line is not desired.

Conversion of Numeric Expression to Text

If the Text-Expansion-Operatoris not the first token on the line or immediately followed by a Text-EquateName, then the argument of the % operator is assumed to be an Expression, which is evaluated and converted to the text representation of its value. This is useful when the need arises to pass the text representation of a number to a macro.

Constraints

When the % Expression form of the expansion operator is used, the Expression must evaluate to an Immediate-ExpressionType.

Examples
MakErr       MACRO       X 
LB           =           0 
             REPEAT      X 
LB           =           LB + 1 
             MakLib      % LB 
             ENDM        ; ; End of REPEAT
             ENDM        ; ; End of MACRO
MakLib       MACRO       Y 
Err & Y :    DB     ' Error    & Y ' ,0 
             ENDM 

             MakErr   3 
Err1 :    DB    ' Error   1 ' ,0
Err2 :    DB    ' Error   2 ' ,0
Err3 :    DB    ' Error   3 ' ,0

Text Substitution Operator (&)

Syntax

Text-Substitution-Operator:

Macro-ParameterName &
& Macro-ParameterName
Description

An ampersand (&) is used in the body of a macro to force the substitution of a Macro-ParameterName with the value of its argument during expansion of the macro.

Constraints

The assembler does not substitute a Macro-ParameterName that is in a quoted string or not preceded by a delimiter in the expansion unless it is immediately preceded by an ampersand (&).

It is necessary to separate a Macro-ParameterName from other Identifer-Characters with an ampersand (&) before any substitution or paste operations are performed.

Examples
ErrGen    MACRO     X 
Error &X: push      bx 
ABX       mov       BX, "A"; 
AB &X     mp        ERROR 
          ENDM

The statement ErrGen A produces this code: 

ErrorA :   push     bx 
ABX        mov      BX , "A"; 
ABA        jmp      ERROR

Preprocessor Tokens

Syntax

Preprocessing-Token:

Identifier
Text-Literal
FileName
Comment
Description

During the text preprocessing translation phase, certain conditions will cause the preprocessor to convert raw #Language Elements (#Tokens) into Preprocessing-Tokens. The act of text preprocessing typically causes Preprocessing-Tokens to either be removed from the input stream or converted back into Tokens before being passed on to the assembler for final processing.

Text Literals

Syntax

Text-Literal:

operand of Literal-Character-Operator
operand of Literal-Text-Operator
Description

A Text-Literal is a single unit of text that is used by the #Text Preprocessor in many different text handling contexts. In some contexts ( such as the processing of arguments to be passed to a macro), normal language #Tokens are implicitly treated as Text-Literals, provided they are not a delimiter character such as a comma or a blank. In other contexts, it may be necessary to explicitly convert a unit of text to a Text-Literal using the Literal-Text-Operator.

Constraints

A normal language Token is never implicitly considered to be a Text-Literal if a Text-Literal is explicitly required in the syntax of the construct being parsed.

File Names

Syntax

FileName:

FileName-Text
Text-Literal

FileName-Text:

FileName-Character
FileName-Text FileName-Character

FileName-Character:

any printable character except blank (ASCII 32)
Description

FileName arguments may be coded as an arbitrary sequence of printable characters, or as a Text-Literal; use the Text-Literal form if the FileName is to contain embedded spaces or other special characters.

If path information is included in the FileName, you can separate the individual directory names with either the back slash (\) or the forward slash (/) and they will be treated identically by the assembler.

Examples
  INCLUDE      <inc\macros.inc> 
  INCLUDELIB   os2386.lib

Comments

Comments are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.

There are two classes of comments recognized by ALP:

  • Comments that start with a character sequence and continue to the end of the line (EndOfLine-Comment)
  • Comments that start with a character sequence and continue until the occurrence of another character sequence (Block-Comment). See the #COMMENT directive for a description of #Block-Comments.

There are two types of EndOfLine-Comments:

Macro-Comment

Macro-Comments (beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of Macro-Comments can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, Macro-Comments are discarded and not entered into the macro definition, whereas NonMacro-Comments are treated as normal text and are retained.

NonMacro-Comment

NonMacro-Comment (beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions.

Syntax

Comment:

EndOfLine-Comment
Block-Comment

EndOfLine-Comment:

NonMacro-Comment
Macro-Comment

NonMacro-Comment:

; Char-Sequence

Macro-Comment:

;; Char-Sequence

Char-Sequence:

any printable character
Char-Sequence any printable character

#Block-Comment:

See the #COMMENT directive
Description

Comments are language elements that have significance only to the programmer and not to the assembler. Comments are effectively removed from the input stream during the text preprocessing phase.

There are two classes of comments recognized by ALP:

  • Comments that start with a character sequence and continue to the end of the line (EndOfLine-Comment)
  • Comments that start with a character sequence and continue until the occurrence of another character sequence (Block-Comment). See the #COMMENT directive for a description of #Block-Comments.

There are two types of EndOfLine-Comments:

Macro-Comment

Macro-Comments (beginning with two semicolons) do not appear in the listing output even when the .LALL directive is used. Use of Macro-Comments can significantly reduce the amount of memory workspace used by the definition of a macro. As a macro definition is read, Macro-Comments are discarded and not entered into the macro definition, whereas NonMacro-Comments are treated as normal text and are retained.

NonMacro-Comment

NonMacro-Comment (beginning with a single semicolon) are preserved in macro definitions and appear in the listing output during macro expansions.

Example

The following are examples of EndOfLine-Comments: 

; Comments may be on a line all by themselves. They can be empty ...
; 
                        ; They don't have to start in the first column
BumpCount MACRO Amount  ; They can appear to the right of statements
  Count = Count + Amount       ; This appears in macro expansions
  $Total = $Total + Amount     ;; This does not, discarded during definition
ENDM

Text Arguments

Many preprocessing directives operate on sequences of raw text characters called Text-Arguments. A Text-Argumentmay be specified using any one of several methods:

  • Specifying the text directly using a raw Text-Literal.
  • Using the Text-Expansion-Operator to convert a numeric expression to its text representation.
  • Using a Text-EquateName in those contexts where a Text-Argumentis expected. In this case the preprocessor will automatically resolve the Text-EquateName and use its value as the Text-Argument.

Text-Argument:

Text-Literal
% Expression
Text-EquateName
Description

Many preprocessing directives operate on sequences of raw text characters called Text-Arguments. A Text-Argumentmay be specified using any one of several methods:

  • Specifying the text directly using a raw Text-Literal.
  • Using the Text-Expansion-Operator to convert a numeric expression to its text representation.
  • Using a Text-EquateName in those contexts where a Text-Argument is expected. In this case the preprocessor will automatically resolve the Text-EquateName and use its value as the Text-Argument.
Syntax

Text-Argument:

Text-Literal
% Expression
Text-EquateName

Conditional Assembly Directives

At assembly time, ALP evaluates conditional assembly directives, assembling if the conditions are true. You can use conditional assembly directives when you want to test for a specified condition and assemble a block of statements if the condition is true. The #IFxx and #ENDIF directives enclose the statements to be considered for conditional assembly. The optional #ELSEIFxx and #ELSE blocks follow the #IFxx directive. There are many forms of the #IFxx and #ELSEIFxx directives.

This section describes the following conditional assembly directives:

#IF
#IFB
#IFDEF
#IFDIF
#IFDIFI
#IFE
#IFIDN
#IFIDNI
#IFNB
#IFNDEF
#IF1
#IF2
#ELSE
#ENDIF

IFxx (Begin Primary Conditional Block)

You can use each IFxxconditional directive with the #ELSExx, #ELSE and #ENDIF directives to provide the statements to be considered for conditional assembly. ALP assembles the statements following the #IFxx directive only if this condition is true.

Syntax 

IFxx   operand
   .
   .
   .
[ ELSEIFxx ]   ( optional )
   .
   .
   .
[ ELSE ]   ( optional )
   .
   .
   .
ENDIF

Remarks

The following directives are members of the IFxx family:

  • IF
  • IFB
  • IFDEF
  • IFDIF
  • IFDIFI
  • IFE
  • IFIDN
  • IFIDNI
  • IFNB
  • IFNDEF
  • IF1
  • IF2

You can nest the conditional directives to any level. They are not limited to use within a macro. The assembler must know any operand to a conditional on pass one to avoid errors and incorrect evaluation.

IF (If Expression is True)

IF starts a conditional assembly statement, which is ended by the corresponding #ENDIF conditional assembly directive. Each IF directive must be ended by a matching ENDIF directive.

Syntax 

IF Expression 
    .
    .
    .
[ ELSEIFxx ]   (optional)
    . 
    . 
    .
[ ELSE ]   (optional)
    .
    .
    .
ENDIF

Remarks

If the #IFxx conditional assembly statement is not ended by an #ENDIF directive, an unterminated conditional message is produced by the assembler. An ENDIF without a matching IF causes an error. ENDIF does not have an operand.

Note: The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.

Example 

IF   debug
     EXTERN   dump:FAR
     EXTERN   trace:FAR
     EXTERN   breakpoint:FAR
ENDIF

IFB (If Argument is Blank)

This is true if #Text-Argument is blank (contains no characters).

Syntax
IFB Text-Argument
Remarks

A #Text-Argument must be specified, the contents of which are checked for the presence of characters. An error is generated if a Text-Argument is not supplied.

IFDEF (If Identifier is Defined)

This is true if #Identifier has been defined as a label, variable, or symbol.

Syntax
IFDEF Identifier

IFDIF (If Arguments Are Different)

This is true if #Text-Argument-1 and Text-Argument-2 are different in a case-sensitive comparison.

Syntax
IFDIF Text-Argument-1, Text-Argument-2
Remarks

Both Text-Argument arguments must be specified. An error is generated if a either argument is not supplied.

Example

In the following example: 

IFDIF <EAGLES>,<Eagles>;
  value = 1
ENDIF

the condition would be true; the arguments are different because they are compared with a case-sensitive algorithm.

IFDIFI (If Arguments Are Spelled Differently)

This is true if #Text-Argument-1 and Text-Argument-2 are different in a case-insensitive comparison.

Syntax
IFDIFI Text-Argument-1, Text-Argument-2
Remarks

Both Text-Argument arguments must be specified. An error is generated if a either argument is not supplied.

Example

In the following example: 

IFDIFI <EAGLES>, <Eagles>
  value = 1
ENDIF

the condition would be false; the arguments are not different because they are compared using a case-insensitive algorithm.

IFE (If Expression is Not True)

This is true if expression is 0.

Syntax 

IFE   Expression

IFIDN (If Arguments Are Identical)

This is true if #Text-Argument-1 and Text-Argument-2 are identical in a case -sensitive comparison.

Syntax 

IFIDN   Text-Argument - 1, Text-Argument - 2

Remarks

Both Text-Argument arguments must be specified. An error is generated if a either argument is not supplied.

Example

In the following example: 

IFIDN   <EAGLES>, <Eagles>; 
  value   =   1 
ENDIF

the condition would be false; the arguments are not identical because they are compared using a case-insensitive algorithm.

IFIDNI (If Arguments Are Spelled Identically)

This is true if #Text-Argument-1 and Text-Argument-2 are identical in a case -insensitive comparison.

Syntax 

IFIDNI   Text-Argument - 1, Text-Argument - 2

Remarks

Both Text-Argument arguments must be specified. An error is generated if a either argument is not supplied.

Example

In the following example: 

IFIDNI <EAGLES>, <Eagles>
  value = 1
ENDIF

the condition would be true; the arguments are identical because they are compared using a case-insensitive algorithm.

IFNB (If Argument is Not Blank)

This is true if Text-Argument is not blank (characters are present).

Syntax 

IFNB Text-Argument

Remarks

A Text-Argument must be specified, the contents of which are checked for the presence of characters. An error is generated if a Text-Argument is not supplied.

IFNDEF (If Identifier is Not Defined)

This is true if symbol has not yet been defined as a label, variable, or symbol.

Syntax 

IFNDEF symbol

IF1 (If Assembling On Pass 1)

This is true on pass one.

Syntax 

IF1

Remarks

IF1 does not have an operand.

IF2 (If Assembling On Pass 2)

This is true on pass two.

Syntax 

IF2

Remarks

IF2does not have an operand.

ELSEIFxx/ELSE (Begin Alternate Conditional Block)

Each conditional directive can be used with the ELSE directive to provide the statements to be considered for conditional assembly. The ELSE directive allows the assembly of the statements following it when the #IFxx condition or intervening ELSEIFxx conditions are false.

Syntax 

IFxx 
    .
    .
    . 
[ ELSEIFxx ]   ( optional ) 
    .
    .
    . 
[ ELSE ]   ( optional ) 
    .
    . 
    . 
ENDIF

Remarks

There is a corresponding ELSEIFxx directive to match all forms of the #IFxx family of directives:

For information about the meaning of the conditional tests performed by the ELSEIFxx directives, refer to the definitions for the corresponding #IFxx directives.

Any number of ELSEIFxx blocks may be used within a given IFxx statement. Only one ELSE block is permitted for a given IFxx. A conditional directive with more than one ELSE or an ELSE without a conditional directive causes an error. ELSE does not have an operand.

Note: The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.

Example 

IF DEFBUF
  BUF DB 100 DUP(0)
ELSE 
  EXTERN BUF:BYTE
ENDIF

ENDIF (End a Conditional Assembly Statement)

ENDIF ends the conditional assembly statement begun by the corresponding #IFxx conditional assembly directive. Each IFxx directive must be ended by a matching ENDIF directive.

Syntax 

IFxx 
    .
    .
    .
[ ELSEIFxx ]   ( optional ) 
    .
    .
    .
[ ELSE ]   ( optional ) 
    .
    .
    .
ENDIF

Remarks

If the #IFxx conditional assembly statement is not ended by an ENDIF directive, an unterminated conditional message is produced by the assembler. An ENDIF without a matching IFxx causes an error. ENDIF does not have an operand.

Note: The conditional directives can be nested to any level. They are not limited to use within a macro. Any operand to a conditional must be known on pass 1 to avoid errors and incorrect evaluation.

Example 

IF  debug
   EXTERN   dump:FAR
   EXTERN   trace:FAR
   EXTERN   breakpoint:FAR
ENDIF

Text Equate Directives

A Text Equate is a symbolic name you give to a series of characters. Text equates are used to expand text within a source statement. The directives described in this section create and manipulate text equates.

EQU
CATSTR
INSTR
SIZESTR
SUBSTR

CATSTR (Concatenate Strings)

CATSTR concatenates a list of text values specified by string into a single text value and assigns it to Name.

Syntax 

Name CATSTR string[, string] ...

EQU Directive (Assign Text to a Symbolic Constant)

The EQU directive assigns the contents of a text literal to Name.

Syntax 

Name EQU   Text - Literal

Remarks

The value of the Text-Literal is assigned to the Name entry. In normal contexts, subsequent references to Name will cause the preprocessor to replace Name with the value specified by the Text-Literal entry. This is a simple text substitution operation.

The Name entry is a globally-scoped Identifier that is converted to a Text-EquateName. The Name cannot have been previously defined as a different Identifier-Type. However, the Name entry can be redefined as many times as desired with different values for the Text-Literal entry.

See also #EQU and #=.

Example 

A   EQU  < BP + >    ; explicit text literal, A is a text equate
A   EQU  < 3 >       ; redefinition of A with different value

INSTR (Search In String For Value)

INSTRsearches a specified String for an occurrence of a given Sub-String and assigns its position (1-based) to Name. The search is case sensitive. Startis the position in String to start the search for Sub-String. If Startis not given, it is assumed to be 1 (the start of the string). If Sub-String is not found, the position assigned to Name is 0.

Syntax 

Name   INSTR   [ Start , ] String , Sub-String

Remarks

INSTRassigns the position value to a name as if it were a numeric equate.

Example 

pos   INSTR   < person > , < son >

SIZESTR (Return Size Of String)

Assigns the number of characters given by the Text-Argument to Name.

Syntax 

Name  SIZESTR  Text-Argument

SUBSTR (Extract a Sub-string From a String)

Assigns a substring of Text-Argument starting at Position to the symbol given by Name..

Syntax 

Name SUBSTR Text-Argument,Position[,Length]

Remarks

The Position parameter indicates the starting character of the substring to extract from the Text-Argument, and must be 1 or greater. If specified, the Length parameter indicates how many characters are desired, otherwise the remainder of the string is extracted.

Macro Directives

A macro procedure or function, which is comprised of one or more statements.

Macro processing is text processing that is done sequentially at assembly time. By the end of assembly, ALP expands all macros and assembles the resulting text into object code.

This section describes the following types of macros:

  • Macro procedures, which expand to one or more complete statements and can optionally take parameters
  • Repeat blocks, which generate a group of statements a specified number of times or until a condition becomes true

This section describes the following macro directives:

ENDM
EXITM
FOR/IRP
FORC/IRPC
LOCAL
MACRO
PURGE
REPEAT/REPT

ENDM (End Current Macro Definition)

End each #MACRO, #REPEAT/REPT, #FOR/IRP, and #FORC/IRPC directive with the ENDMdirective.

Syntax
ENDM
Remarks

If the ENDM directive is not used with the #MACRO, #REPEAT/REPT, #FOR/IRP, and #FORC/IRPC directives, an error occurs. An unmatched ENDM also causes an error.

If the assembler produces an error message stating that it found the end-of -file on the source and cannot find an #END statement when there was an END, the likely cause is a missing ENDM or ENDIF statement. Without ENDM, the assembler treats the rest of the source as part of the #MACRO definition.

Note: The name field is not allowed. Do not confuse the ENDM directive with other ending directives that do require the name of the block being ended, such as ENDP or ENDS.

Example 

addup   MACRO     ad1, ad2, ad3
        MOV       AX, ad1         ;; first parameter in AX
        ADD       AX, ad2         ;; add next two parameters 
        ADD       AX, ad3         ;; leave sum in AX
        ENDM

EXITM (End Current Macro Expansion)

Use the EXITM directive when a block contains a directive that tests for some condition and you want to end the current macro expansion when the test proves that the remainder of the expansion is not required. When an EXITM directive is run, the expansion is stopped immediately, and any remaining expansion or repetition is not produced.

Syntax 

EXITM
Remarks

Only the block containing the EXITM directive is ended; outer levels of a nested macro expansion continue unaffected.

EXITM is executed at macro expansion time and is not a substitute for the #ENDM directive, which marks the end of the macro body and is recognized at macro definition time.

Example 

DSEG   SEGMENT 
      .
      .
      .
SYM   =   0 
    REPEAT 16
; ; Check for paragraph boundary
      IF   ( $ - DSEG ) MOD 16 EQ 0
      EXITM   ; ; quit if padded to boundary
      ENDIF 
SYM = SYM + 1 
      DB   SYM   ; ; produce numbered padding
      ENDM

FOR/IRP (Iterative Macro Expansion Using List of Arguments)

The FOR directive, used in combination with the #ENDM directive, designates a block of statements to be repeated, once for each argument in the list enclosed by angle brackets. Each repetition substitutes the next item in the <Argument-List> entry for every occurrence of Parameter in the block.

Syntax 

FOR  Parameter , < Argument-List >
    .
    .
    .
ENDM
Remarks

The obsolete spelling for the FOR directive is IRP.

You must enclose the <Argument-List> entry in angle brackets. It has the following format: 

< [ Argument   [ ,   Argument   . . . ] ] >

If an empty (<>) Argument is found in <Argument-List>, the Parameter name is replaced by a null value. If the argument list is empty, the FORdirective is ignored and no statements are copied. The assembler processes the block once for each Argumentin the <Argument-List>, replacing each occurrence of Parameterin the macro body with the current Argument value.

The #FOR/IRP-#ENDM block does not have to be within a macro definition.

Example

In this example, the assembler produces the code DB1 through DB10. 

FOR     X ,   < 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 > 
DB      X 
ENDM

In the next example: 

FOR      ARGUMENT , < " first   line " , 13 , 10 , 
" second   line " , 13 , 10 > 
DB      ARGUMENT 
ENDM

The assembler produces the code: 

DB     " first   line " 
DB     13 
DB     10 
DB     " second   line " 
DB     13 
DB     10

FORC/IRPC (Iterative Macro Expansion Using List of Characters)

The assembler repeats the statements in the block once for each character in the string. Each repetition substitutes the next character in the string for every occurrence of Parameterin the block.

Syntax 

FORC   Parameter ,  String ( or < String > ) 
    .
    .
    .
ENDM

Remarks

The obsolete spelling for the FORCdirective is IRPC.

The FORCdirective is similar to the #FOR/IRP directive except that a String is used instead of <Argument-List>, and the angle brackets around the string are optional. The string should be enclosed with angle brackets (<>) if it contains spaces, commas, or other separating characters.

The FORC/IRPC-#ENDM block does not have to be within a macro definition.

Example

In this example, the assembler produces the code DB 1 through DB 8: 

FORC      X, 12345678
DB        X
ENDM

LOCAL (Identify Names Local to a Macro Definition)

The LOCAL directive is used inside the body of a macro definition, and provides a method of automatically generating unique assembler labels each time the macro is expanded. The names appearing in the argument list of the LOCAL directive are known only to the enclosing macro, and each time they are referenced during a macro expansion a unique symbol is created. This prevents the assembler from issuing duplicate definition errors when the macro is expanded more than once and symbols contained therein are being used to create assembler labels.

Syntax
LOCAL Name [, Name .... ]
Remarks

The LOCAL directive is recognized only within the body of a macro given by a #MACRO, #FOR/IRP, #FORC/IRPC, or #REPEAT/REPT definition. The symbols created by the preprocessor are of the form ??nnnn, where nnnn is a hexadecimal number in the range 0000 through FFFF. You must avoid using identifiers of this form for your own purposes, because doing so can cause duplicate definition errors.

To insure that they have the proper effect, LOCAL statements should appear in the body of the macro before any other directives are used. It is acceptable for blank lines or comments to precede any LOCAL statements.

You can use multiple LOCAL statements if the argument list is too long to fit on one line, or if you want a vertical list of LOCAL symbols.

Example
DISPLAY MACRO TT 

; Blank lines and comments are ok here
      LOCAL AGAIN 

;; DOS macro to display message addressed by BX TT times
      MOV     CX, TT
      MOV     AH, 9
      MOV     DX, BX
; Generate a unique label for AGAIN
AGAIN:
      INT     21H 
      LOOP    AGAIN 
      ENDM

MACRO (Assign a Body of Text to a Name)

This directive produces a given sequence of statements from various places in your program, even though different parameters may be required each time you call the sequence.

Macro processing consists of two separate and distinct phases: #Macro Definition and #Macro Expansion.

Macro Definition

A macro definition consists of three essential parts:

  • The MACRO directive, defining the Name and the Parameter-List
  • The body of the macro, containing the prototypes of statements to produce when you invoke the macro for expansion.
  • The #ENDM directive, ending the definition of the macro.
Syntax
Name MACRO [Parameter [, Parameter ...]]
  .
  .
  .
ENDM
Remarks

The Name field must be a valid preprocessor identifier and specifies the symbolic name that the user will refer to when invoking the macro for expansion. If Name is already defined, it must be that of a previous macro definition, otherwise an error message is issued. Macros may be redefined to have a different Parameter-Lists or macro body text; doing so causes the previous definition to be lost.

The optional Parameter-List is the complete comma-separated list of all Parameter valuess given in the macro definition statement. A parameter must be a valid symbol name according to the rules for naming preprocessor and assembler identifiers. Each parameter becomes a symbol that is local to the macro being defined and is recognized during macro expansion prior to searching the global name space. Thus, macro parameters need not have names unique from identifiers defined elsewhere in the program.

Macro Expansion

To expand the macro, the macro Name (defined in the Name field of the MACRO definition statement) is coded as you would any other assembler directive, followed by the list of arguments (if any) that you want to pass to the macro.

Syntax
Name [Argument [, Argument ...]]
Remarks

The Name field must be the name of a macro defined previously with a MACRO directive.

Each Argument field denotes a text value that you want to pass to the macro. The relative positions of the elements are important, because each Argument is associated in left-to-right fashion with the corresponding Parameter as defined in the Parameter-List during the macro definition.

The number of Argument entries given when the macro is invoked need not be the same as the number of Parameter entries. If you pass extra Arguments to the macro, they are ignored; if too few are supplied, empty text values are associated with the remaining Parameters. You may also associate an empty text value with a Parameter by passing an explicitly empty text literal <> as an Argument.

Commas are normally used to separate arguments, although blanks or tabs are also considered to be argument separators. For this reason, any argument that must contain an argument separator character (commas, blanks, or tabs) should be enclosed in angle brackets <>. For example: 

PUSHVEC   MACRO   PARM1, PARM2
          MOV     AX, PARM1
          PUSH    AX
          MOV     AX, PARM2
          PUSH    AX
          ENDM
          .
          .
          .
          PUSHVEC   DS, <OFFSET VARNAME>
 ; PUSH DWORD VECTOR OF VARNAME ONTO STACK

You can also use angle brackets to produce variable lengths of results. For example: 

STRING   MACRO     NUMBERS
         DB        NUMBERS
         ENDM
           .
           .
           .
         STRING   <1,2,3,4>
         ; PRODUCE 4 BYTES OF INTEGER NUMBERS
Remarks

Each time a macro is invoked (expanded) by specifying its name, the preprocessor emits the statements contained in the body of the macro and passes them to the assembler for processing. During the expansion process, any replacement parameters encountered in the macro body (as named in the Parameter-List of the macro definition) are replaced with the corresponding Argument (if any) passed through the argument-list at the time the macro was invoked.

Example
GEN   MACRO   XX, YY, ZZ
      MOV     AX, XX
      ADD     AX, YY
      MOV     ZZ, AX
      ENDM

When the call is made, for example: 

GEN   ED, KISER, SUM

The assembler produces the following code: 

MOV     AX, ED
ADD     AX, KISER 
MOV     SUM, AX

PURGE (Remove Macro Definition)

The PURGE directive deletes the definition of a specified macro entry, letting you reuse space.

Syntax
PURGE Macro-Name [, ...]
Remarks

It is not necessary to purge a macro before redefining it. You may use PURGE to recover memory during assembly by deleting the contents of unreferenced macros. An Out of Memory condition can occur if a large, general-purpose macro library is included.

Example

The directive: 

PURGE     MACRONAME

performs the same function as redefining the macro with no contents, as in: 

MACRONAME MACRO
          ENDM

In the following example, assume that MAC1 is a macro included in MACRO.LIB: 

INCLUDE   MACRO.LIB
PURGE     MAC1
MAC1      ; Calls the purged macro
          ; but produces nothing

REPEAT/REPT (Iterative Macro Expansion Using a Count Expression)

REPEAT specifies the number of times to generate the statements inside the macro.

Syntax
REPEAT Expression
 Statements
ENDM
Remarks

The Expression field must evaluate to an Absolute-ExpressionType (it cannot contain forward references). Because the repeat block will be expanded at assembler time, the number of iterations must be known then.

ECHO Directive (Display Message on Standard Output Device)

The ECHO directive displays progress through a long assembly or displays the value of conditional assembly parameters.

Syntax 

ECHO Text

Remarks

The assembler lists the Text entry on the standard output device during assembly when the assembler encounters the ECHO directive.

ECHO is not available under MASM 5.10 emulation; you must use %OUT, which is the obsolete spelling for the ECHO directive.

Example

Example 1: 

IF IBM
  ECHO IBM VERSION
ENDIF 

IF2
  ECHO STARTING SECOND PASS
   .
   .
   .
  ENDIF

Example 2: 

INNER   MACRO    TEXT, VAL
        ECHO     TEXT  VAL 
        ENDM
        .
        .
        .
HERE    =  $ - CSEG 
        INNER <CURRENT LOCATION>,%HERE

INCLUDE Directive (Insert File Contents into Input Stream)

The INCLUDE directive "stacks" the current source file and begins reading tokens from the source file given by the FileName argument. If you use the INCLUDE directive, you need not repeat a sequence of statements that are common to several source files.

Syntax 

INCLUDE FileName

Remarks

The assembler uses the following search order when attempting to open the INCLUDE file:

  1. If the FileName argument contains a fully qualified path name (one that begins with a back slash or forward slash), then the assembler attempts to open the file exactly as specified, and no other search is performed if the file is not found.
  2. If the FileName begins with a relative path name or contains no path information, the assembler begins searching for the INCLUDE file by looking in the directory of the source file that issued the INCLUDE directive.
  3. The assembler searches for FileName in the list of directories given by any #-Fdi or #-I options found on the command line.
  4. The assembler searches for FileName in the list of directories given by the <BaseEXE>_INCLUDE environment variable.
  5. The assembler searches for FileName in the list of directories given by the INCLUDE environment variable.
  6. Lastly, the assembler searches for FileName in the current directory. If the named file is not found, the assembler issues a fatal error message and the assembler is ended.

In no case does the assembler strip relative path information from the FileName when performing search steps 2 through 6.

When the file named in the INCLUDE directive is located, the assembler opens it and assembles all of the statements contained therein until the end of the file is reached. The file is then closed and assembler resumes in the original module at the line following the INCLUDE directive.

An INCLUDE file should not contain an #END assembler directive to denote the end of the included module; the assembler closes the included module when its physical end of file is reached.

INCLUDE files may be nested to any reasonable level, and is limited only by the operating system's ability to provide the necessary resources.

Example
INCLUDE OS2.INC

COMMENT Directive (Program Information Block)

COMMENT lets you enter comments about your program without having to enter semicolons (;) for each line.

Syntax
COMMENT   Delimiter   Text   Delimiter
Remarks

The first non-blank character after COMMENT is the first delimiter. The COMMENT directive causes the assembler to treat all Text between Delimiter and Delimiter as a comment. The text must not contain the delimiter character. This directive is used for multiple-line comments. A COMMENT defined in the body of a macro does not appear unless .LALL is requested.

Example 

COMMENT *You can enter as many lines
of text between the delimiters
   .
   .
   .
as you need to describe your program.*

Return Codes

When ALP completes, it passes a return code back to the program that invoked it. This return code shows whether ALP completed successfully or with an error. The return codes are:

  • 0 Normal program completion.
  • 1 User-specified file not found.
  • 2 Unexpected system error.
  • 3 Terminated by user or operating system.
  • 4 Syntax errors in input file.
  • 5 Command line usage error.
  • 6 Internal sanity check failure.
  • 7 Error accessing ALP messages file.

Notices

October 1997

The following paragraph does not apply to the United Kingdom or any country where such provisions are inconsistent with local law:

INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS". WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.

This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this publication at any time.

It is possible that this publication may contain reference to, or information about, IBM products (machines and programs), programming, or services that are not announced in your country. Such references or information must not be construed to mean that IBM intends to announce such IBM products, programming, or services in your country.

Requests for technical information about IBM products should be made to your IBM authorized reseller or IBM marketing representative. (C) Copyright International Business Machines Corporation 1995-1997. All rights reserved. Note to U.S. Government Users -- Documentation related to restricted rights -- Use, duplication or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.

The #Processor Reference portion of this manual contains information reprinted with permission from Intel Corporation.

Disclaimers

References in this publication to IBM products, programs, or services do not imply that IBM intends to make these available in all countries in which IBM operates. Any reference to an IBM product, program or service is not intended to state or imply that only IBM's product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any of IBM's intellectual property rights or other legally protectable rights may be used instead of the IBM product, program, or service. Evaluation and verification of operation in conjunction with other products, programs, or services, except those expressly designated by IBM, are the user's responsibility.

IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to the IBM Director of Licensing, IBM Corporation, 500 Columbus Avenue, Thornwood NY 10594, U.S.A.

Trademarks

The following terms are trademarks of the IBM Corporation in the United States or other countries:

IBM
Operating System/2
OS/2
Presentation Manager

The following terms are trademarks of other companies:

Microsoft - Microsoft Corporation
Pentium - Intel Corporation Pentium Pro - Intel Corporation
UNIX - UNIX System Laboratories, Inc.
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