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 color

The color assigned to a background 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.

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)

Code that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard.

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.

BIOS

Basic Input/Output System.

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 (bitblt)

Transfer of a rectangular array of bit-map data.

bitblt

Bit-block transfer.

bit map

A representation of an image by an array of bits.

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.

Bit block transfer (bitblt)

The process of transferring one or more blocks of data.

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.

border

A visual indicator of a window's boundaries.

boundary determination

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

BPB

BIOS Parameter Block.

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.

broken pipe

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

bucket

One or more fields in which the result of an operation is kept.

buffer

(1) A portion of storage used to hold input or output data temporarily.

(2) To allocate and schedule the use of buffers. (A)

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.

button

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

byte

A logical data unit composed of eight binary digits (bits).

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.

byte stream

Data that consists of an unbroken stream of bytes.