DDK Glossary - E

EBCDIC

Extended binary-coded decimal interchange code. A coded character set consisting of 8-bit coded characters (9 bits including parity check), used for information interchange among data processing systems, data communications systems, and associated equipment.

edge-triggered

Pertaining to an event semaphore that is posted then reset before a waiting thread gets a chance to run. The semaphore is considered to be posted for the rest of that thread's waiting period; the thread does not have to wait for the semaphore to be posted again.

EGA

Extended graphics adapter.

element

An entry in a graphics segment that comprises one or more graphics orders and that is addressed by the element pointer.

EMS

Expanded Memory Specification. Enables DOS applications to access memory above the 1 MB real mode addressing limit.

encapsulation

Hiding an object's implementation, that is, its private, internal data and methods. Private variables and methods are accessible only to the object that contains them.

entry field

In SAA Common User Access architecture, an area where a user types information. Its boundaries are usually indicated. See also selection field.

entry panel

A defined panel type containing one or more entry fields and protected information such as headings, prompts, and explanatory text.

entry point

1. In a database, the record that is first accessed upon entry into a database, caused by a user's command.
2. The address or label of the first instruction executed on entering a computer program, routine, or subroutine. A computer program, routine, or subroutine may have a number of different entry points, each perhaps corresponding to a different function or purpose. Synonymous with entrance, entry.
3. In a routine, any place to which control can be passed.
4. In the C, FORTRAN, and Pascal languages, the address or label of the first instruction processed or entered in a program, routine, or subroutine. A program, routine, or subroutine can have a number of different entry points, each corresponding to a different function or purpose.

entry-field control

The component of a user interface that provides the means by which the application receives data entered by the user in an entry field. When it has the input focus, the entry field displays a flashing pointer at the position where the next typed character will go.

environment segment

The list of environment variables and their values for a process.

environment strings

ASCII text strings that define the value of environment variables.

environment variables

Variables that describe the execution environment of a process. These variables are named by the operating system or by the application. Environment variables named by the operating system are PATH, DPATH, INCLUDE, INIT, LIB, PROMPT, and TEMP. The values of environment variables are defined by the user in the CONFIG.SYS file, or by using the SET command at the OS/2 command prompt.

EOI

End Of Interrupt

error message

An indication that an error has been detected. (A)

event semaphore

A semaphore that enables a thread to signal a waiting thread or threads that an event has occurred or that a task has been completed. The waiting threads can then perform an action that is dependent on the completion of the signaled event.

exception

An abnormal condition such as an I/O error encountered in processing a data set or a file.

exclusive system semaphore

A system semaphore that can be modified only by threads within the same process.

executable file

(1) A file that contains programs or commands that perform operations or actions to be taken. (2) A collection of related data records that execute programs.

exit

To execute an instruction within a portion of a computer program in order to terminate the execution of that portion. Such portions of computer programs include loops, subroutines, modules, and so on. (T) Repeated exit requests return the user to the point from which all functions provided to the system are accessible. Contrast with cancel.

extended attribute

An additional piece of information about a file object, such as its data format or category. It consists of a name and a value. A file object may have more than one extended attribute associated with it.

extended help

In SAA Common User Access architecture, a help action that provides information about the contents of the application window from which a user requested help. Contrast with contextual help.

extended-choice selection

A mode that allows the user to select more than one item from a window. Not all windows allow extended-choice selection. Contrast with multiple-choice selection.

extent

Continuous space on a disk or diskette that is occupied by or reserved for a particular dataset, data space, or file.

external link

In Information Presentation Facility, a link that connects external online document files.