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Backup
A copy of all of your important files usually stored on removable media such as a magnetic tape or cd-rom.

Bad Sector
An area on a hard or floppy disk that cannot be used to store data due to damage caused by accident, wear, or manufactring defect.

Bash Shell
An extension of the original Bourne shell. Tab key file-name completion is one such feature that makes it easy to use. Supports powerfuls test on files and directories. It has two modes of operation for its command-line editing and command-history mechanism. Available on all modern versions of Linux, UNIX, and other operating systems.

Binary file
A file stored in binary format. A binary file is computer -readable but not human-readable. All executable programs are stored in binary files, as are most numeric data files. In contrast, text files are stored in a form (usually ASCII) that is human-readable.

Binary Language
Base-two number system, of which the only digits are 0 and 1. Used as a signal for processing as either off (0) or on (1), from left to right the digits have a binary value of 1, 2, 4, 8, 16, and so on (the binary number of 101, for instance, is equivalent to the decimal number, 5.

BIOS
Basic Input Output System. This is a set of instructions stored in non-volitile memory (meaning that it is not erased when the power is shut down) that allow the operating system to communicate with the system hardware.

Bits
Short for binary digit, the smallest unit of information on a machine. A single bit can hold only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units. For example, a byte is composed of 8 consecutive bits.

Bookmark
To mark a document or a specific place in a document for later retrieval. Nearly all Web browsers support a bookmarking feature that lets you save the address (URL) of a Web page so that you can easily re-visit the page at a later time.

Boot
The process of loading the operating system into memory and passing control of the computer to the operating system.

Bourne Shell
A public domain program from the Free Software Foundation.

Buffer
A temporary storage area, usually in RAM. The purpose of most buffers is to act as a holding area, enabling the CPU to manipulate data before transferring it to a device.

Bug
A logical error in software or hardware that causes the computer to behave unexpectedly.

Bus
An electronic pathway used for parts of the computer to communicate with one another.