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bandwidth
A measure of how much information something can carry. Specifically, data path times
frequency. For example, the ISA bus has a data path of 16 bits (it can send 16 bits at a time)
and typically operates at 8.33 MHz, so it has a bandwidth of 133.28 megabits per second
(Mbps).
base RAM
Area of system memory between 0 and 640 kilobytes available to the user for operating
system and application programs.
batch file
A file that contains a series of DOS commands. Batch files have the extension .bat. If you
execute a batch file, DOS attempts to carry out all the commands in the file, in order.
baud
A unit of measure for modem speed. Literally, the number of voltage transitions per second.
Phone line limitations limit the actual baud rate of modems to 2400 baud, although the data
transmission rate (bps) may be higher because of data compression.
BBS
Short for Bulletin Board Service. Software that serves as a communication and information
source for computers that communicate by modem.
BIOS
Basic Input/Output System. A program or set of programs permanently stored in ROM
chips installed on the system board. The BIOS contains functions that control the real-time
clock, keyboard, disk drives, video display, and other peripheral devices. For example, the
BIOS Setup utility program is contained in the BIOS, and when you change the drive type,
you change the BIOS.
bit
Binary digit. The smallest unit of computer data. A single digital piece of information,
generally represented by the numeral 0 or 1. Usually the transition between the states of
+5V and -5V within a computer, the charge of a transistor in an integrated circuit, or the
change in polarity of a magnetic region on a disk. See byte. Data compression schemes can
enable the transmission of more than one bit per voltage transition.
bit block transfer
Moving part of a screen image as a single block rather than moving a pixel at a time. Bit
block transfers are much faster than moving the same pixels individually, and it is common
in accelerated video cards.
bitBLT
Bit Block Transfer.
bitmap
Any occurrence where a single location in memory and a single pixel correspond. Usually
applies to screen or printer output. All .BMP files are bitmapped graphics files.
bits per second
(bps) A unit of transmission. Also called baud rate.
Glossary 3
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