B picture

See bidirectionally-coded picture (B picture).

backing store

A mass-storage device such as a disk that serves as backup "memory" for paging when physical memory is full.

See also paging file.

balance set

The set of processes whose threads are eligible for execution.

A process is either included in or excluded from the balance set. A kernel-mode process remains in the balance set while any of its threads owns a mutex object. Each thread that owns one or more mutexes continues to run until it releases its last mutex, when the thread is suspended. Until every thread has released every mutex, the process remains part of the balance set.

At any given moment, the balance set depends on the amount of physical memory (pages) available to back the virtual address space associated with each active process. If a physical memory shortage occurs, the memory manager first reduces the working set for each active process to its minimum, and then removes processes from the balance set, if necessary.

See also dispatch state and working set.


See banked memory.

bank manager

Code that maps banked memory for CPU access.

banked callback

A callback routine provided by the display drive to enable GDI to access banked memory. GDI cannot directly access banked memory that is associated with a banked frame buffer. Consequently, the display driver of a device with such a frame buffer must divide the frame buffer into a series of contiguous banks and provide a means for GDI to perform its draw operations to the appropriate frame buffer banks. That is, GDI is made to write data to one bank of the frame buffer before being moved to subsequent banks, as necessary, to complete the draw operation through a mechanism referred to as "banked callbacks."

banked memory

Memory that is partitioned into distinct blocks. Prior to the advent of PCI devices, most video cards could expose only 64 KB of video memory to the system at a time. This memory was present at physical address 0xa0000. The video card typically had considerably more than 64 KB of memory, and would map views of this larger frame buffer into the 64-KB window. This process was referred to as banking. A bank is one 64-KB block of the frame buffer. The current bank is the bank that is visible to the CPU.

based section

A section allocated at the same virtual address for each process that has a view of the section.

See also section object and view.

basic input/output system (BIOS)

A set of low-level routines that works closely with the hardware to support the transfer of information between elements of the system, such as memory, disks, and the monitor. Although critical to performance, the BIOS is usually invisible to the end user; however, programmers can access it.

Basic Service Set (BSS)

A cell in an 802.11 LAN. An 802.11 LAN uses a cellular architecture that divides the system into a number of cells.

Basic Service Set identifier (BSSID)

Identifies a Basic Service Set (BSS).


See buffer control block (BCB).

bidirectionally-coded picture (B picture)

A picture type that uses the closest past I or P picture and the closest future I or P picture as the reference for motion-compensated prediction.


A computer architecture in which the byte layout of memory is as follows:

  • Byte N is the most significant byte of:
    • A word composed of bytes N and (N + 1).
    • A doubleword composed of bytes N, (N + 1), (N + 2), and (N + 3).
    • A K-byte memory entity composed of bytes N, (N + 1),...,(N + K − 1).
  • The address of a word, doubleword, or K-byte entity is the address of its most significant byte, N.

Some RISC processors can be configured for either big-endian or byte addressing. For a big-endian configuration, the most significant bit of a 16-bit value is the leftmost bit at byte N, while the least significant bit is the rightmost bit of byte (N + 1).

The terms "big-endian" and "little-endian" are derived from Jonathan Swift's Gulliver's Travels.

See also little-endian.


See basic input/output system (BIOS).

BIOS enumerator

In a non-ACPI Plug and Play system, the BIOS enumerator identifies the hardware devices on the motherboard of the computer. The BIOS supports a programming interface that allows all Plug and Play computers to be queried in a common manner.

bit-block transfer

A programming technique that manipulates blocks of bits in memory that represent the color and other attributes of a rectangular block of pixels forming a screen image. The bit block is moved through a computer's video RAM as a unit so that its pixels can be rapidly displayed in a desired location on the screen. The bits can also be altered: light and dark portions of an image can be reversed, for example. Successive displays can thus be used to change the appearance of an image or to move it around on the screen. Some computers contain special graphics hardware to manipulate bit blocks on the screen independently of the contents of the rest of the screen. This speeds the animation of small shapes, because a program need not constantly compare and redraw the background around the moving shape. Also called bitblt, blt, or blit.

A stretched bit-block transfer copies a rectangular block of pixels to a rectangle of different size at a different location.

A nonstretched bit-block transfer copies a rectangular block of pixels to a rectangle of the same size at a different location.


See standard format bitmap.

bits per pixel (BPP)

The number of bits used to represent the color value of each pixel in a digitized image.

bits per second (BPS)

The number of bits transferred per second in a data communications system. A measure of speed.


See bit-block transfer.

boot-start driver

A driver that is required to start the system.

For more information, see the topic Installing a Boot-Start Driver.


See bits per pixel (BPP).


See bits per second (BPS).


See ISDN basic rate interface.

bridge pin

The physical connection at the endpoint of a graph. A bridge pin cannot be used to connect to another pin except through KSPROPERTY_PIN_PHYSICALCONNECTION. An instance of a bridge pin may have properties or methods that can be used to manipulate that endpoint, for example a file source endpoint.


The value that is associated with a pixel to represent its gray value, ranging from black to white.


A content delivery method in which one or more clients receive a stream. During a broadcast connection, clients cannot control the stream.

broadcast architecture

The set of technologies that enable PCs to receive broadcast data.

brush origin

The coordinate of a pixel on a device's surface that is aligned with the upper left pixel of the brush's pattern.


A GDI user object that contains information that describes a brush object. Brush objects are used to define fill patterns.


See Basic Service Set identifier (BSSID).

buffer control block (BCB)

An opaque cache manager structure that is used to maintain state as a file system pins and releases data (for example, its volume structure) in the cache.

bug check

A system-detected error that causes an immediate, controlled shutdown of the system. If a kernel-mode component discovers an unrecoverable error, it generates a bug check by calling KeBugCheck or KeBugCheckEx. For more information, see Interpreting Bug Check Codes.

bus enumerator

See enumerator.



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