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DDK Glossary - C

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Glossary

cache
A high-speed buffer storage that contains frequently accessed instructions and data; it is used to reduce access time.
cached micro presentation space
A presentation space from a Presentation-Manager-owned store of micro presentation spaces. It can be used for drawing to a window only, and must be returned to the store when the task is complete.
CAD
Computer-Aided Design.
CAI
Computer-assisted instruction. Synonym for CBT.
calibration
The adjustment of a piece of equipment so that it meets normal operational standards. (For example, for the IBM InfoWindow system, calibration refers to touching a series of points on the screen so that the system can accurately determine their location for further reference.)
call
(1) The action of bringing a computer program, a routine, or a subroutine into effect, usually by specifying the entry conditions and jumping to an entry point. (I) (A) (2) To transfer control to a procedure, program, routine, or subroutine.
calling sequence
A sequence of instructions together with any associated data necessary to execute a call. (T)
camcorder
A compact, hand-held video camera with integrated videotape recorder.
Cancel
An action that removes the current window or menu without processing it, and returns the previous window.
capture
To take a snapshot of motion video and retain it in memory. The video image may then be saved to a file or restored to the display.
cascaded menu
In the OS/2 operating system, a menu that appears when the arrow to the right of a cascading choice is selected. It contains a set of choices that are related to the cascading choice. Cascaded menus are used to reduce the length of a menu. See also cascading choice.
cascading choice
In SAA Common User Access architecture, a choice in a menu that, when selected, produces a cascaded menu containing other choices. An arrow (→) appears to the right of the cascading choice.
CASE statement
In PM programming, provides the body of a window procedure. There is usually one CASE statement for each message type supported by an application.
cast animation
(1) A sequence of frames consisting of manipulations of graphical objects. (2) The action of bringing a computer program, routine, or subroutine into effect, usually by specifying the entry conditions and jumping to an entry point. (3) See also frame animation.
CAV
Constant angular velocity.
CBT
Computer-based training. Synonym for CAI.
CCITT
Comite Consultatif International Telegraphique et Telephonique. The International Telegraph and Telephone Consultative Committee.
CDB
Command Descriptor Block. The structure used to communicate commands from a source to a destination.
CD
Compact disc.
CD-DA
Compact disc, digital audio.
CD-I
Compact Disc-Interactive.
CD-ROM
Compact disc, read-only memory.
CD-ROM XA
Compact disc, read-only memory extended architecture.
cel
A single frame (display screen) of an animation. (The term originated in cartooning days when the artist drew each image on a sheet of celluloid film.)
CF IOProc
An internal I/O procedure, provided by the MMPM/2 system, that supports RIFF compound files. The CF IOProc operates on the entire compound file (rather than on the elements in a RIFF compound file, as with the BND IOProc). The CF IOProc is limited to operations required by the system to ensure storage system transparency at the application level. See also BND IOProc.
CGA
Color graphics adapter.
CGRP
Compound file resource group.
channel mapping
The translation of a MIDI channel number for a sending device to an appropriate channel for a receiving device.
channel message
A type of non-SysEx MIDI message that has a channel identifier in it, implying that these messages are specific to one channel.
character
A letter, digit, or other symbol.
character box
(1) In computer graphics, the boundary that defines, in world coordinates, the horizontal and vertical space occupied by a single character from a character set. See also character mode. Contrast with character cell. (2) An imaginary parallelogram on a display surface that contains all parts of one graphic character. Synonymous with bounding box. (T) (3) The maximum area in which a symbol and all associated elements, such as a cursor, an underline, or space surrounding the symbol to separate it from other symbols, can be printed or displayed. Synonymous with character cell. (4) The imaginary parallelogram whose boundaries govern the size, orientation, and spacing of individual characters to be displayed on a graphics display device.
character cell
(1) The physical, rectangular space in which any single character is displayed on a screen or printer device. Position is addressed by row and column coordinates. Contrast with character box. (2) An addressable location on a display surface or printing medium. (3) The physical width and height in pels of a font. See also bounding box. (4) The imaginary box whose boundaries govern the size, orientation, and spacing of individual characters to be displayed on a workstation.
character code
The means of addressing a character in a character set, sometimes called code point.
character device
A device that performs I/O operations on one character at a time. Because character devices view data as a stream of bytes, character-device data cannot be randomly accessed. Character devices include the keyboard, mouse, and printer, and are referred to by name.
character mode
A mode that, in conjunction with the font type, determines the extent to which graphics characters are affected by the character box, shear, and angle attributes.
character set
(1) An ordered set of unique representations called characters; for example, the 26 letters of the English alphabet, Boolean 0 and 1, the set of symbols in the Morse code, and the 128 ASCII characters. (A) (2) All the valid characters for a programming language or for a computer system. (3) A group of characters used for a specific reason; for example, the set of characters a printer can print.
check box
In SAA Advanced Common User Access architecture, a square box with associated text that represents a choice. When a user selects a choice, an X appears in the check box to indicate that the choice is in effect. The user can clear the check box by selecting the choice again. Contrast with radio button.
check disc
A videodisc produced from the glass master that is used to check the quality of the finished interactive program.
check mark
(1) (D of C) In SAA Advanced Common User Access architecture, a symbol that shows that a choice is currently in effect. (2) The symbol that is used to indicate a selected item on a pull-down menu.
child process
In the OS/2 operating system, a process started by another process, which is called the parent process. Contrast with parent process.
child window
A window that appears within the border of its parent window (either a primary window or another child window). When the parent window is resized, moved, or destroyed, the child window also is resized, moved, or destroyed; however, the child window can be moved or resized independently from the parent window, within the boundaries of the parent window. Contrast with parent window.
choice
(1) An option that can be selected. The choice can be presented as text, as a symbol (number or letter), or as an icon (a pictorial symbol). (2) (D of C) In SAA Common User Access architecture, an item that a user can select.
chord
(1) To press more than one button on a pointing device while the pointer is within the limits that the user has specified for the operating environment. (2) (D of C) In graphics, a short line segment whose end points lie on a circle. Chords are a means for producing a circular image from straight lines. The higher the number of chords per circle, the smoother the circular image. (3) To press and release more than one button at a time on a pointing device.
chroma-key color
The specified first color in a combined signal. See also chroma-keying.
chroma-keying
Combining two video signals that are in sync. The combined signal is the second signal whenever the first is of some specified color, called the chroma-key color, and is the first signal otherwise. (For example, the weatherman stands in front of a blue background—blue is the chroma-key color.) At home, the TV viewer sees the weather map in place of the chroma-key color, with the weatherman suspended in front.
chroma signal
The portion of image information that provides the color (hue and saturation).
chrominance
The difference between a color and a reference white of the same luminous intensity.
chunk
(1) The basic building block of a RIFF file. (2) A RIFF term for a formalized data area. There are different types of chunks, depending on the chunk ID. (3) See LIST chunk and RIFF chunk.
chunk ID
A four-character code (FOURCC) that identifies the representation of the chunk data.
circular slider control
A knob-like control that performs like a control on a TV or stereo.
circular slider knob
A knob-like control that operates like a control on a television or stereo.
class
(1) A categorization or grouping of objects that share similar behaviors and characteristics. Synonym for object class. (2) A way of categorizing objects based on their behavior and shape. A class is, in effect, a definition of a generic object. In SOM, a class is a special kind of object that can manufacture other objects that all have a common shape and exhibit similar behavior (more precisely, all of the objects manufactured by a class have the same memory layout and share a common set of methods). New classes can be defined in terms of existing classes through a technique known as inheritance. (3) See node class. (RTMIDI-specific term)
class method
A class method of class <X> is a method provided by the metaclass of class <X>. Class methods are executed without requiring any instances of class <X> to exist, and are frequently used to create instances. In System Object Model, an action that can be performed on a class object.
class object
In System Object Model, the run-time implementation of a class.
class style
The set of properties that apply to every window in a window class.
click
To press and release a button on a pointing device without moving the pointer off the choice. See double-click. See also drag select.
client
(1) A functional unit that receives shared services from a server. (T) (2) A user, as in a client process that uses a named pipe or queue that is created and owned by a server process.
client area
The part of the window, inside the border, that is below the menu bar. It is the user's work space, where a user types information and selects choices from selection fields. In primary windows, it is where an application programmer presents the objects that a user works on.
client program
An application that creates and manipulates instances of classes.
client window
The window in which the application displays output and receives input. This window is located inside the frame window, under the window title bar and any menu bar, and within any scroll bars.
clip
A section of recorded, filmed, or videotaped material. See also audio clip and video clip.
clip limits
The area of the paper that can be reached by a printer or plotter.
clipboard
In SAA Common User Access architecture, an area of computer memory, or storage, that temporarily holds data. Data in the clipboard is available to other applications.
clipping
In computer graphics, removing those parts of a display image or elements that lie outside a given boundary. (I) (A)
clipping area
The area in which the window can paint.
clipping path
A clipping boundary in world-coordinate space.
CLOCK$
Character-device name reserved for the system clock.
closed circuit
A system of transmitting television signals from a point of origin to one or many restricted destination points specially equipped to receive the signals.
close-up
In videotaping, the picture obtained when the camera is positioned to show only the head and shoulders of a subject; in the case of an object, the camera is close enough to show details clearly. See also extreme close-up.
CLP
Common loader primitive.
CLUT
Color look-up table. Synonym for color palette.
CLV
Constant linear velocity.
code page
An assignment of graphic characters and control-function meanings to all code points; for example, assignment of characters and meanings to 256 code points for an 8-bit code, assignment of characters and meanings to 128 code points for a 7-bit code.
code point
(1) Synonym for character code. (2) (D of C) A 1-byte code representing one of 256 potential characters.
CODEC
Compressor/decompressor (CODEC) - An algorithm implemented either in hardware or software that can either compress or decompress a data object. For example, a CODEC can compress raw digital images into a smaller form so that they use less storage space. When used in the context of playing motion video, decompressors reconstruct the original image from the compressed data. This is done at a high rate of speed to simulate motion.
code segment
An executable section of programming code within a load module.
collaborative document production
A system feature that provides the ability for a group of people to manage document production.
collision
An unwanted condition that results from concurrent transmissions on a channel. (T) (For example, an overlapping condition that occurs when one sprite hides another as it passes over it.)
color conversion
Changing one color format to another. Required, for example, when the source color format is different from the destination color format. When going from the monochrome color format to the color format, 1 (one) bits are converted to the image foreground color, and 0 (zero) bits are converted to the image background color. When going from color to monochrome, all pels that match the passed background color are converted to the image background color of the destination. All other pels are converted to the image foreground color of the destination. The color conversion takes place prior to any mix mode.
color cycling
An animation effect in which colors in a series are displayed in rapid succession.
color dithering
See dithering.
color graphics adapter (CGA)
An adapter that simultaneously provides four colors and is supported by all IBM Personal Computer and Personal System/2 models.
color palette
(1) A set of colors that can be displayed on the screen at one time. This can be a standard set used for all images or a set that can be customized for each image. (2) Synonym for CLUT. (3) See also standard palette and custom palette.
colorization
The color tinting of a monochrome original.
COM1, COM2, COM3
Character-device name reserved for serial ports 1 through 3.
command
The name and parameters associated with an action that a program can perform.
command area
An area composed of a command field prompt and a command entry field.
command code
Refers to a group of related commands that an adapter device driver can receive. All command codes have a prefix of "IOCC_". For example, common I/O requests (such as Read, Write, etc.) are grouped under the command code IOCC_EXECUTE_IO.
command data block
A data structure defined by the Small Computer System Interface standard to send commands to devices that conform to SCSI standards.
command descriptor block (CDB)
The structure used to communicate commands from a source to a destination.
command entry field
An entry field in which users type commands.
command line
On a display screen, a display line, sometimes at the bottom of the screen, in which only commands can be entered.
command mode
A state of a system or device in which the user can enter commands.
command modifier
A specific operation that an adapter device driver is to perform. All command modifiers have a prefix of "IOCM_". For example, an adapter device driver might receive an IOCC_EXECUTE_IO command with a command modifier of IOCM_READ.
command prompt
A field prompt showing the location of the command entry field in a panel.
Common Programming Interface (CPI)
Definitions of those application development languages and services that have, or are intended to have, implementations on and a high degree of commonality across the SAA environments. One of the three SAA architectural areas. See also Common User Access architecture.
Common User Access (CUA) architecture
Guidelines for the dialog between a human and a workstation or terminal. One of the three SAA architectural areas. See also Common Programming Interface.
common loader primitive
A system service that provides a high-level interface to hardware-specific loaders.
common user access (CUA)
(1) Guidelines for the dialog between a human and a workstation or terminal. (2) One of the three SAA architectural areas.
compact disc (CD)
A disc, usually 4.75 inches in diameter, from which data is read optically by means of a laser.
compact disc, digital audio (CD-DA)
The specification for audio compact discs. See also Redbook audio.
Compact Disc-Interactive (CD-I)
A low-cost computer, being developed by N.V. Phillips (The Netherlands) and Sony (Japan), that plugs into standard television sets to display text and video stored on compact discs.
compact disc, read-only memory (CD-ROM)
High-capacity, read-only memory in the form of an optically read compact disc.
compact disc, read-only memory extended architecture (CD-ROM XA)
An extension to CD-ROM supporting additional audio and video levels for compression and interlacing of audio, video, and digital data.
compatibility kernel
The portion of the OS/2 kernel that exists to support DOS INT 20, 21, 25, 26, and 27 functions. It acts as an interface to common kernel functionality such as the file system.
compile
To translate a program written in a higher-level programming language into a machine language program.
component video
A video signal using three signals, one of which is luminance, and the other two of which are the color vectors. See also composite video and S-video.
composed view
A view of an object in which relationships of the parts contribute to the overall meaning. Composed views are provided primarily for data objects.
composite
The combination of two or more film, video, or electronic images into a single frame or display. See also composite video.
composite monitor
A monitor that can decode a color image from a single signal, such as NTSC or PAL. Contrast with RGB.
composite object
An object that contains other objects. For example, a document object that contains not only text, but graphics, audio, image, and/or video objects, each of which can be manipulated separately as an individual object.
composite video
A single signal composed of chroma, luminance, and sync. NTSC is the composite video that is currently the U.S. standard for television. See also component video and S-video.
compound device
A multimedia device model for hardware that requires additional data objects, referred to as data elements, before multimedia operations can be performed.
compound file
A file that contains multiple file elements.
compound file resource group (CGRP)
A RIFF chunk that contains all the compound file elements, concatenated together.
compound file table of contents (CTOC)
A RIFF chunk that indexes the CGRP chunk, which contains the actual multimedia data elements. Each entry contains the name of, and other information about, the element, including the offset of the element within the CGRP chunk. All the CTOC entries of a table are of the same length and can be specified when the file is created.
compound message
A structure which combines a time stamp, a source instance identifier, a track number, and a MIDI message. Each of these fields is 32 bits, so the structure is 16 bytes in length. (RTMIDI-specific term)
computer-animated graphics
Graphics animated by using a computer, compared to using videotape or film.
computer-assisted instruction (CAI)
(1) A data processing application in which a computing system is used to assist in the instruction of students. The application usually involves a dialog between the student and a computer program. An example is the OS/2 tutorial. (2) Synonym for computer-based training.
computer-based training (CBT)
Synonym for computer-assisted instruction.
computer-controlled device
An external video source device with frame-stepping capability, usually a videodisc player, whose output can be controlled by the multimedia subsystem.
conditional cascaded menu
A pull-down menu associated with a menu item that has a cascade mini-push button beside it in an object's pop-up menu. The conditional cascaded menu is displayed when the user selects the mini-push button.
conditional compilation
Processing by the preprocessor of certain specified code in the file, depending on the evaluation of a specified condition.
conforming
Performing final editing on film or video using an offline edited master as a guide.
connection
The establishment of the flow of information from a connector on one device to a compatible connector on another device. A connection can be made that is dependent on a physical connection, for example the attachment of a speaker to an audio adapter with a speaker wire. A connection can also be made that is completely internal to the PC, such as the connection between the waveaudio media device and the ampmix device. See also connector.
connector
A software representation of the physical way in which multimedia data moves from one device to another. A connector can have an external representation, such as a headphone jack on a CD-ROM player. A connector can also have an internal representation, such as the flow of digital information into an audio adapter. See also connection.
constant angular velocity (CAV)
Refers to both the format of data stored on a videodisc and the videodisc player rotational characteristics. CAV videodiscs contain 1 frame per track. This allows approximately 30 minutes of playing time per videodisc side. CAV videodisc players spin at a constant rotational speed (1800 rpm for NTSC or 1500 rpm for PAL) and play 1 frame per disc revolution. CAV players support frame-accurate searches. See also constant linear velocity.
constant linear velocity (CLV)
Refers to both the format of data stored on a videodisc and the videodisc player characteristics. CLV videodiscs contain 1 frame on the innermost track and 3 frames of data on the outermost track. This allows approximately 1 hour of playing time per videodisc side. CLV videodisc players vary the rotational speed from approximately 1800 rpm at the inner tracks to 600 rpm at the outer tracks (for NTSC). Currently, few CLV players support frame-accurate searches. They only support search or play to within one second (30 frames for NTSC or 25 frames for PAL). See also constant angular velocity.
container
(1) An object whose specific purpose is to hold other objects. A folder is an example of a container object. (2) In SAA Common User Access architecture, an object that holds other objects. A folder is an example of a container object. See also folder and object.
contents view
A view of an object that shows the contents of the object in list form. Contents views are provided for container objects and for any object that has container behavior, for example, a device object such as a printer.
context hook
Similar to a "force flag" in earlier versions of OS/2. These are events, signaled by a virtual device driver, that are processed at task time. Forcing an IRET, and simulating an NMI, can fall into this category.
contextual help
In SAA Common User Access Architecture, help that gives specific information about the item the cursor is on. The help is contextual because it provides information about a specific item as it is currently being used. Contrast with extended help.
contiguous
Touching or joining at a common edge or boundary, for example, an unbroken consecutive series of storage locations.
continuity
In videotaping, consistency maintained from shot to shot and throughout the take. For example, a switch that is on in one shot should not be off in the next unless it was shown being turned off.
continuous media object
A data object that varies over time; a stream-oriented data object. Examples include audio, animation, and video.
contrast
The difference in brightness or color between a display image and the area in which it is displayed. A contrast level of 0 is minimum difference. A contrast level of 100 is maximum difference.
control
(1) A visual user interface component that allows a user to interact with data. (2) In SAA Advanced Common User Access architecture, a component of the user interface that allows a user to select choices or type information; for example, a check box, an entry field, a radio button.
control area
A storage area used by a computer program to hold control information. (I) (A)
Control Panel
In the Presentation Manager, a program used to set up user preferences that act globally across the system.
control program
(1) The basic functions of the operating system, including DOS emulation and the support for keyboard, mouse, and video input/output. (2) A computer program designed to schedule and to supervise the execution of programs of a computer system. (I) (A)
controller sector buffer
One or more buffers, managed by a hardware adapter, to improve I/O transfer rates by helping to match a device and software timing requirements.
control window
A window that is used as part of a composite window to perform simple input and output tasks. Radio buttons and check boxes are examples.
control word
An instruction within a document that identifies its parts or indicates how to format the document.
coordinate graphics
(1) Computer graphics in which display images are generated from display commands and coordinate data. (2) Contrast with raster graphics. (3) Synonym for line graphics.
coordinate space
A two-dimensional set of points used to generate output on a video display or printer.
Copy
A choice that places onto the clipboard, a copy of what the user has selected. See also Cut and Paste.
correlation
The action of determining which element or object within a picture is at a given position on the display. This follows a pick operation.
coverpage window
A window in which the application's help information is displayed.
crop
To cut off; to trim (for example, a tape).
crossfade
Synonym for dissolve.
cross-platform
Used to describe applications that are operable with more than one operating system.
cross-platform transmission
Electronic transmission of information (such as mail) between incompatible operating systems.
CTOC
Compound file table of contents.
CU
Script abbreviation for close-up.
CUA
Common User Access.
cue point
A point that the system recognizes as a signal that may be acted upon.
custom palette
(1) A set of colors that is unique to one image or one application. (2) See also standard palette and color palette.
Cut
In SAA Common User Access architecture, a choice that removes a selected object, or a part of an object, to the clipboard, usually compressing the space it occupied in a window. See also Copy and Paste.
cursor
A symbol displayed on the screen and associated with an input device. The cursor indicates where input from the device will be placed. Types of cursors include text cursors, graphics cursors, and selection cursors. Contrast with pointer and input focus.
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