DDK Glossary - A

ABIOS

Advanced BIOS. See BIOS.

AB roll

Synchronized playback of two recorded video images so that one can perform effects, such as dissolves, wipes, or inserts, using both images simultaneously.

accelerator

In SAA Common User Access architecture, a key or combination of keys that invokes an application-defined function.

accelerator table

A table used to define which key strokes are treated as accelerators and the commands they are translated into.

access mode

The manner in which an application gains access to a file it has opened. Examples of access modes are read-only, write-only, and read/write.

access permission

All access rights a user has regarding an object. (I)

accumulator

A register in which one operand of an operation can be stored and subsequently replaced by the result of that operation. (T)

In the IBM 3800 Printing Subsystem Models 3 and 8, a feature that supplies a separate storage that can hold data in raster form. It can be used either for composing a sheet of data that combines a large amount of variable and constant data, or for storing an electronic overlay in raster form that will be merged with variable data as the sheet is printed.

ACPA

Audio capture and playback adapter.

action

One of a set of defined tasks that a computer performs. Users request the application to perform an action in several ways, such as typing a command, pressing a function key, or selecting the action name from an action bar or menu.

action bar

In SAA Common User Access architecture, the area at the top of a window that contains choices that give a user access to actions available in that window.

action point

The current position on the screen at which the pointer is pointing. Contrast with hot spot and input focus.

active program

A program currently running on the computer. An active program can be interactive (running and receiving input from the user) or noninteractive (running but not receiving input from the user). See also interactive program and noninteractive program.

active matrix

A technology that gives every pel (dot) on the screen its own transistor to control it more accurately. (This allows for better contrast and less motion smearing.)

active window

The window with which the user is currently interacting.

adapter

A piece of hardware that modifies the system unit to allow it to operate in a particular way, often by connecting the system unit to an external device such as a video monitor.

adapter device driver

A device driver that provides hardware-dependent services for an OEM adapter.

adaptive differential pulse code modulation

A bit-rate reduction technique where the difference in pulse code modulation samples are not compressed before being stored.

ADC

Analog-to-digital converter.

address conversion

The process of converting a 0:32 memory reference to the 16:16 addressing scheme, and vice versa.

address space

(1) The range of addresses available to a program. (A)

(2) The area of virtual storage available for a particular job.

address translation

(1) The process of resolving a 0:32 memory reference into a physical memory address. When using the paged memory option in the 80386 processor, a memory pointer passed by an application consists of Page Directory and Page Table entries, and an offset within a physical page. This is resolved by the processor into a 32-bit physical memory address. The validity and legality of the memory reference is also checked during the translation process, and a general protection exception is generated if necessary.

(2) The process of resolving a 16:16 memory reference into a physical memory address using a process's local descriptor table. The validity and legality of the memory reference is also checked during the translation process, and a general protection exception is generated if necessary.

ADPCM

Adaptive differential pulse code modulation.

alias

Term used in the 80386 segmented memory model, to refer to the case where two different addresses reference the same physical memory location; the location is said to be aliased. This technique is used when sharing memory between processes, and when mapping memory references between 16:16 and 0:32 addressing schemes.

aliasing

The phenomenon of generating a false (alias) frequency, along with the correct one, as an artifact of sampling a signal at discrete points. In audio, this produces a "buzz." In imagery, this produces a jagged edge, or stair-step effect. See also moire.

all points addressable (APA)

In computer graphics, pertaining to the ability to address and display or not display each picture element (pel) on a display surface. (Also abbreviated as APA).

alphanumeric video output

Output to the logical video buffer when the video adapter is in text mode and the logical video buffer is addressed by an application as a rectangular array of character cells.

AM

Animation metafile.

ambience

In audio, the reverberation pattern of a particular concert hall, or listening space.

ambient noise

In acoustics, the noise associated with a particular environment, usually a composite of sounds from many distant or nearby sources.

American National Standard Code for Information Interchange

The standard code, using a coded character set consisting of 7-bit coded characters (8 bits including parity check), that is used for information interchange among data processing systems, data communication systems, and associated equipment. The ASCII set consists of control characters and graphic characters. (A) Note: IBM has defined an extension to ASCII code (characters 128-255).

American National Standards Institute (ANSI)

An organization consisting of producers, consumers, and general interest groups, that establishes the procedures by which accredited organizations create and maintain voluntary industry standards in the United States.

AMF

Animation metafile format.

amp

See amplifier.

amplifier

(1) A device that increases the strength of input signals (either voltage or current). (2) Also referred to as an amp.

amp-mixer

(1) A combination amplifier and mixer that is used to control the characteristics of an audio signal from one or more audio sources. (2) Also referred to as an amplifier-mixer.

analog

Pertaining to data consisting of continuously variable physical quantities. Contrast with digital.

analog audio

Audio in which all information representing sounds is stored or transmitted in a continuous-scale electrical signal, such as line level audio in stereo components. See also digital audio.

analog-to-digital converter (ADC)

A functional unit that converts data from an analog representation to a digital representation. (I) (A)

analog video

Video in which all the information representing images is in a continuous-scale electrical signal for both amplitude and time. See also digital video.

analog video overlay

See overlay.

anchor

An area of a display screen that is activated to accept user input. Synonymous with hot spot, touch area, and trigger. A window procedure that handles Presentation Manager message conversions between an icon procedure and an application.

anchor block

An area of Presentation Manager internal resources allocated to a process or thread that calls WinInitialize.

anchor point

The position or choice from which selection or deselection is extended. Also, a point in a window used by a program designer or by a window manager to position a subsequently appearing window.

animate

Make or design in such a way as to create apparently spontaneous, lifelike movement.

animated

Having the appearance of something alive.

animated screen capture

Recording a computing session for replay on a similar computer with voice annotation. (An example is sending a spreadsheet with an accompanying screen recording as an explanation and overview.)

animatic

A limited animation consisting of artwork shot on film or videotape and edited to serve as an on-screen storyboard.

animation metafile

A compound file format, the elements of which are the frames of animation themselves. These frames are stored sequentially so that they can be played back in time by streaming to the video agent.

animation metafile format (AMF)

The file format used to store animated frame sequences.

annotation

The linking of an object with another, where the second contains some information related to the first. For example, an audio annotation of a spreadsheet cell might contain verbal explanation about the contents of the cell.

ANSI

American National Standards Institute.

anthropomorphic software agent

The concept of a simulated agent, seemingly living inside the computer, that talks to and listens to the user, and then acts for the user on command.

antialiasing

(1) In imagery, using several intensities of colors (a ramp) between the color of the line and the background color to create the effect of smoother curves and fewer jagged edges on curves and diagonals. (2) In imagery or audio, removing aliases by eliminating frequencies above half the sample frequencies.

AOCA

Audio Object Content Architecture.

APA

All points addressable.

APA graphics

All Points Addressable graphics. See bitmap graphics.

API

Application programming interface.

application

A collection of software components used to perform specific types of work on a computer; for example, a payroll application, an airline reservation application, a network application.

application object

In SAA Advanced Common User Access architecture, a form that an application provides for a user; for example, a spreadsheet form. Contrast with user object.

application programming interface (API)

A functional interface supplied by the operating system or an IBM separately orderable licensed program that allows an application program written in a high-level language to use specific data or functions of the operating system or the licensed program.

application-modal

Pertaining to a message box or dialog box for which processing must be completed before further interaction with any other window owned by the same application may take place.

application-supplied video window

(1) An application can specify to MMPM/2 that it wants video played in a specific window (controlled by the application) instead of the default window (controlled by MMPM/2). The application supplied video window can be used to implement advanced features not supported by the default video window. (2) Also referred to as an alternate video window.

archive flag

In the OS/2 operating system, a flag of files and directories that the operating system uses to determine which files are new or modified. Files with this flag are included when a backup copy is made or when all the files are restored on a hard disk. See flag.

area

In computer graphics, a filled shape such as a solid rectangle.

arena

Refers to a contiguous subset of the processor's virtual address space. In OS/2 V2.0, arenas are used to manage regions of the linear address space.

artifact

A product resulting from human activity; in computer activity, a (usually unwanted) by-product of a process.

ASCII

American National Standard Code for Information Interchange.

ASCIIZ

A string of ASCII characters that is terminated with a byte containing the value 0.

aspect ratio

(1) The ratio of the height of a rectangle to its width. A rectangle of width 10 inches and height 5 inches has an aspect ratio of 10/5 or 2.

(2) On a display screen, the ratio of the maximum length of a display line to the maximum length of a display column.

(3) In computer graphics, the width-to-height ratio of an area, symbol, or shape.

asymmetric video compression

In multimedia applications, the use of a powerful computer to compress a video for mastering so that a less powerful (less expensive) system is needed to decompress it. Contrast with symmetric video compression.

asynchronous (ASYNC)

(1) Pertaining to two or more processes that do not depend upon the occurrence of specific events such as common timing signals. (T)

(2) Without regular time relationship; unexpected or unpredictable with respect to the execution of program instructions. See also synchronous.

atom

A constant that represents a string. Once a string has been defined as an atom, the atom can be used in place of the string to save space. Strings are associated with their respective atoms in an atom table.

atom table

A table used to associate atoms with the strings that they represent. This table contains the mechanism by which the presence of a string can be verified.

atomic operation

An operation that completes its work on an object before another operation can be performed on the same object.

attribute

A characteristic or property that can be controlled, usually to obtain a required appearance; for example, the color of a line. See also graphics attributes and segment attributes.

audible cue

A sound generated by the computer to draw a user's attention to, or provide feedback about, an event or state of the computer. Audible cues enhance and reinforce visible cues.

audio

Pertaining to the portion of recorded information that can be heard.

audio attribute control

Provides access to and operation of the standard audio attributes: mute, volume, balance, treble, and bass. All device communication and user interface support is handled by the control.

audio attributes

Refers to the standard audio attributes: mute, volume, balance, treble and bass.

audio clip

A section of recorded audio material.

Audio Object Content Architecture

A data format for multimedia products.

audio processing

Manipulating digital audio to, for example, edit or create special effects.

audio segment

A contiguous set of recorded data from an audio track. An audio segment might or might not be associated with a video segment.

audio track

(1) The audio (sound) portion of the program. (2) The physical location where the audio is placed beside the image. (A system with two audio tracks can have either stereo sound or two independent audio tracks.) (3) Synonym for sound track.

audiovisual

A generic term referring to experiences, equipment, and materials used for communication that make use of both hearing and sight.

Audio Visual Connection* (AVC)

An authoring system used on an IBM PS/2* to develop and display audiovisual productions.

audiovisual computer program

A computer program that makes use of both hearing and sight.

authoring

A structured approach to combining all media elements within an interactive production, assisted by computer software designed for this purpose.

authoring system

A set of tools used to create an interactive multimedia application without implementing formal programming.

automatic link

In Information Presentation Facility (IPF), a link that begins a chain reaction at the primary window. When the user selects the primary window, an automatic link is activated to display secondary windows.

AVIO

Advanced Video Input/Output.

AVI file format

The Audio/Video Interleaved (AVI) file format is the standard file format used to support software motion video. AVI files can contain multiple streams (tracks) of data (for example, a video and an audio stream). The streams are interleaved to improve access times during playback. The present implementation is limited to a single video stream and a single, optional, audio stream.