The s

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back door		A way of getting into a password-protected system without using the password. Usually a carefully guarded secret to prevent misuse.
backbone		A central network that connects two or more less powerful networks.
backup		To store data in an archive, especially a duplicate copy of a program. Also the archive itself.
bad sector		Part of a hard or floppy disk storage medium that doesn't hold data. Formatting generally detects and marks these areas so they won't be used. Certain utility programs do too, and it is a good idea to run this type of utility occasionally to prevent data loss if the condition of the disk changes.
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 8.33MHz, so it has a bandwidth of 133.28 megabits per second.
bank		A row of similar components used as a single device. They must be installed or removed together. Also a convenient section of memory. See bank switching.
bank switching		A way to expand the useful amount of RAM in a computer by switching (the data in) banks of memory to addresses that are accessible to the microprocessor. DOS is able to address only 640K of memory. Computers with more memory use bank switching to access the extra memory. See expanded memory.
base memory		The first 640K of computer memory.
BASIC		Beginner's All-purpose Symbolic Instruction Code. A widespread programming language. A version of BASIC is included with DOS. The filenames of programs written in BASIC frequently end in .BAS.
.BAT		See batch file.
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.
BatteryMark		This benchmark from Ziff Davis Labs measures battery life on notebook computers running Windows 95.
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. (The term baud comes from the name of a French inventor, J. M. E. Baudot.)
bay		An opening in the chassis to hold mass storage devices such as hard disks, floppy disks, CD-ROM drives, and tape backup units.
BBS		Short for Bulletin Board System. Software that serves as a communication and information source for computers that communicate by modem.
benchmark		A program or procedure which tests or evaluates the relative performance characteristics of computer systems or peripherals.
benefit		The reason why a feature is attractive. For example, the benefit of a notebook computer's light weight is that it is easy to carry. See feature.
binary		A number system that uses only two digits, 0 and 1. Called a base 2 number system. Place value indicates powers of 2. (In the decimal system, place value indicates powers of 10.) Since computers use bits, which have only two states, binary is a convenient number system for representing computer information at its most basic level.
BIOS		(by-ose) 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 enable the CPU to communicate with the outside world. For example, the Setup utility is contained in the BIOS, and when you change the drive type, you change the BIOS.
bit		Short for Binary Digit. A single digital piece of information, generally represented by the numeral 0 or 1. The smallest piece of information that a computer deals with. Usually the transition between the states of +5V and -5V within a desktop 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. Algorithms for moving and copying rectangles of bits between main and display memory on a bit-mapped device, or between two areas of either main or display memory.
bitmap		Any situation in which a single location in memory and a single pixel correspond. Usually applies to screen or printer output. .BMP files are bitmapped graphics files.
bitmapped font		A font whose characters are described in terms of the locations of bits on the screen (or on paper) that show the shapes of the characters. Since bitmapped fonts are constructed at specific sizes, you frequently see jagged shapes if you display the letters at a different size. For example, a bitmapped 12 point font looks terrible at 17 points. Compare outline font.
block		A contiguous section of bits considered as a whole, especially in memory. On a disk, the data in one sector; in modem data transfer, the bits between checksums.
.BMP		(bump) The usual extension for the filename of a certain high resolution bitmap graphics file usualy found in the Windows environment. .BMP files can be used as wallpaper in Windows.
bomb		When a computer fails to operate, usually due to a failure in software. Used especially if the screen shows conspicuously incorrect behavior, such as rapid blinking. Usually requires rebooting the computer.
Boolean		The type of logical operation that computers perform. When you see AND, OR, XOR, IF, or NOT, they're referring to Boolean functions. Everything a computer does can be described in Boolean statements. Named after George Boole, who invented the branch of mathematics called Boolean algebra.
boot		To start the computer system. Your computer is generally booted in one of three ways: by turning on the power switch, by pressing the reset switch, or by simultaneously pressing the Ctrl, Alt, and Del keys. Booting the system after it has already been powered up and booted is referred to as rebooting. Also the process of booting itself. Boot is from "bootstrap;" a reference to a computer's ability to set itself up, or pull itself up by its own "bootstraps".
bootable device		Any type of hardware that carries the information (software) required by the computer to start properly. This device must also have the capacity to be recognized by the computer in the first stages of the boot process.
boot block		The part of a disk that contains the software (such as the operating system loader) that enables the computer to start.
boot sector		The part of the boot block that contains the operating system loader, a program that starts by itself and loads the operating system.
bps		Bits Per Second. The number of bits of data that can be transmitted in one second. Because data compression schemes enable more than one bit per voltage transition, bps is equivalent to baud only if no compression is used.
break		A special signal that interrupts and terminates the execution of a program or command. Frequently ^C (Ctrl+C) or the signal sent by the Break key on the keyboard. Also, to cause software to malfunction, especially deliberately, as when testing the software.
bridge		A device that connects two or more similar local area networks.
brown out		A period of time during which line voltage drops seriously, usually because of unusually high demands on the power utility. A computer exposed to a brown out can suffer data loss and physical damage.
browser		A program designed to view and navigate hypertext.
buffer		A place, especially in RAM, for the temporary storage of data for the purpose of speeding up an operation such as printing or disk access. Data from a buffer is available more quickly than data from where the buffer got it. Typically buffers get data before it is needed so it will be ready quickly when it is needed. Similar to cache.
bug		An unintentional error in programming that makes a program malfunction. Said to originate from a moth caught in a relay in an early computer.
burst mode		When a device seizes control of the bus, sends data, then relinquishes control of the bus. Any time a device sends data without interruption instead of taking turns with other devices.
burst speed		With reference to dot matrix printers, burst speed refers to the speed of the printer without taking into account any function (such as carriage returns) that slows down actual printing. This gives the highest possible speed for the printer.
bus		A parallel electrical pathway, usually part of the circuit board, connecting and shared by the parts of a computer system, especially the CPU, its support circuitry, memory, and expansion cards. Typically the lines in a bus are dedicated to specific functions, such as control lines, address lines, and data lines. Different bus architectures have different numbers and arrangements of these lines, and different names (e.g. NuBus, IEEE, ISA, EISA). The most useful way of distinguishing bus architectures is by the number of simultaneous data bits they can carry. The old PC bus could transmit 8 bits at once; the AT bus (ISA) is a 16-bit bus, and therefore is twice as fast, other things being equal.
bus clock speed		The frequency at which a bus runs.
bus master		The ability of an expansion card to control the bus without needing intervention from the CPU.
bus topology		A network in which all the nodes are connected as branches from a single main line. A network in which all the nodes are connected as branches from a single main line, like the teeth of a comb. Compare Token Ring.
byte		Eight bits. See bit. The basic "word" of digital signals. Frequently written as an eight-digit binary number or a two-digit hexadecimal number. One letter of the alphabet in ASCII code takes one byte.

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