DDK Glossary - B

background: (1) In multiprogramming, the conditions under which low-priority programs are executed. Contrast with foreground.; (2) An active session that is not currently displayed on the screen.

background image: The part of a display image, such as a form overlay, that is not changed during a particular sequence of transactions. Contrast with foreground image.

background mix: An attribute that determines how the background of a graphic primitive is combined with the existing color of the graphics presentation space.

background program: In multiprogramming, a program that executes with a low priority. Contrast with foreground program.

balance: For audio, refers to the relative strength of the left and right channels. A balance level of 0 is left channel only. A balance level of 100 is right channel only.

base device driver: An OS/2 device driver that performs I/O during the OS/2 kernel boot sequence to provide IPL support. Base device drivers are loaded by way of the CONFIG.SYS BASEDEV keyword, rather than the DEVICE keyword. See BASEDEV keyword, adapter device driver, and device manager.

BASEDEV keyword: New CONFIG.SYS keyword; loads a base device driver into the operating system.

basic input/output system (BIOS): In an IBM personal computer, microcode that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard. (For example, the IBM Enhanced Graphics Adapter has an addressable BIOS, located on the adapter itself, that is used to control the IBM InfoWindow* graphics functions.)

Bezier curve: A mathematical technique of specifying a smooth, continuous line or surface, requiring a starting point and an ending point, with several intermediate points that influence or control the path of the linking curve.

Bidi: Bidirectional; term used to describe support for national languages such as Arabic and Hebrew, which use bidirectional character sets.

bit: A binary digit, which may be either zero or one. Bits are represented within a computing device by the presence or absence of an electrical or magnetic pulse at a particular point, indicating a one or a zero respectively.

bit-block transfer: Transfer of a rectangular array of bitmap data. Synonym for bitblt.

bitmap: A coded representation in which each bit, or group of bits, represents or corresponds to an item, for example, a configuration of bits in main storage in which each bit indicates whether a peripheral device or a storage block is available or in which each group of bits corresponds to one pel of a display image.

bitmap graphics: A form of graphics whereby all points on the display are directly addressable. See also all points addressable.

block: (1) In programming languages, a compound statement that coincides with the scope of at least one of the declarations contained within it. A block may also specify storage allocation or segment programs for other purposes. (I); (2) A string of data elements recorded or transmitted as a unit. The elements may be characters, words or physical records. (T); (3) A collection of contiguous records recorded as a unit. Blocks are separated by interblock gaps and each block may contain one or more records. (A)

block device: A storage device that performs I/O operations on blocks of data called sectors. Data on block devices can be randomly accessed. Block devices are designated by a drive letter (for example, C:).

blocking mode: A condition set by an application that determines when its threads might block. For example, an application might set the Pipemode parameter for the DosCreateNPipe function so that its threads perform I/O operations to the named pipe block when no data is available.

BND: (1) An internal I/O procedure, provided by the MMPM/2 system, that supports RIFF compound files (commonly called bundle files). (2) The four-character code (FOURCC) of a bundle file. (3) See also RIFF compound file.

BND IOProc: An internal I/O procedure, provided by the MMPM/2 system, that supports the elements in a RIFF compound file. See also CF IOProc.

Boot Manager: Feature of OS/2 Version 2.0 which allows multiple partitions to exist on fixed disks in the same machine, with a separate operating system on each partition. At boot time, the user may select the desired operating system with which to start the machine.

boot name: A name used to refer to a selectable logical drive under Boot Manager, from which an operating system may be started.

boom: A long, relatively horizontal supporting brace used for holding a microphone or camera; sometimes used to refer to the machinery that supports the camera and allows it to move while shooting.

boundary determination: An operation used to compute the size of the smallest rectangle that encloses a graphics object on the screen.

breakpoint: (1) A point in a computer program where execution may be halted. A breakpoint is usually at the beginning of an instruction where halts, caused by external intervention, are convenient for resuming execution. (T); (2) An instruction in a program for halting execution. Breakpoints are usually established at positions in a program where halts, caused by external intervention, are convenient for restarting. (T); (3) A place in a program, specified by a command or a condition, where the system halts execution and gives control to the workstation user or to a specified program.

brightness: Refers to the level of luminosity of the video signal. A brightness level of 0 produces a maximally white signal. A brightness level of 100 produces a maximally black signal.

broken pipe: When all of the handles that access one end of a pipe have been closed.

buffer: (1) A portion of storage used to hold input or output data temporarily.; (2) To allocate and schedule the use of buffers. (A)

bundle file (BND): (1) A file that contains many individual files, called file elements, bound together. The MMIO file manager provides services to locate, query, and access file elements in a bundle file. (2) A RIFF compound file.

Bus Master adapter: An adapter capable of performing Reads and Writes to physical storage by communicating directly with the storage subsystem (memory) rather than depending on a host DMA channel or host CPU. Synonymous with first-party DMA adapter.

bus: A facility for transferring data between several devices located between two end points, only one device being able to transmit at a given moment.

button: A mechanism used to request or initiate an action. See also barrel buttons, bezel buttons, mouse button, push button, and radio button.

buy: (1) In videotaping, footage that is judged acceptable for use in the final video. (2) Synonym for keeper.

byte pipe: Pipes that handle data as byte streams. All unnamed pipes are byte pipes. Named pipes can be byte pipes or message pipes. See byte stream.