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Glossary Of Computer Terms



   

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B: n. Short for byte.

backbone: n. 1. A network of communication transmission that carries major traffic between smaller networks. The backbones of the Internet, including communications carriers such as Sprint and MCI, can span thousands of miles using microwave relays and dedicated lines. 2. The smaller networks (compared with the entire Internet) that perform the bulk of the packet switching of Internet communication. Today these smaller networks still consist of the networks that were originally developed to make up the Internet--the computer networks of the educational and research institutions of the United States--especially NSFnet, the computer network of the National Science Foundation in Oak Ridge, Tennessee. See also NSFnet, packet switching. 3. The wires that carry major communications traffic within a network. In a local area network, a backbone may be a bus. Also called collapsed backbone.

backbone cabal: n. On the Internet, a term for the group of network administrators responsible for naming the hierarchy of Usenet newsgroups and devising the procedures for creating new newsgroups. The backbone cabal no longer exists.

back door: n. A means of gaining access to a program or system by bypassing its security controls. Programmers often build back doors into systems under development so that they can fixs bugs. If the back door becomes known to anyone other than the programmer, or if it is not removed before the software is released, it becomes a security risk. Also called trapdoor.

back end: n. 1. In a client/server application, the part of the program that runs on the server. See also client/server architecture. Compare front end. 2. The part of a compiler that transforms source code (human-readable program statements) into object code (machine-readable code). See also compiler (definition 2), object code, source code.

back-end processor: n. 1. A slave processor that performs a specialized task such as providing rapid access to a database, freeing the main processor for other work. Such a task is considered "back-end" because it is subordinate to the computer's main function. 2. A processor that manipulates data sent to it from another processor; for example, a high-speed graphics processor dedicated to painting images on a video display operates in response to commands passed "back" to it by the main processor. Compare coprocessor.

background1: adj. In the context of processes or tasks that are part of an operating system or program, operating without interaction with the user while the user is working on another task. Background processes or tasks are assigned a lower priority in the microprocessor's allotment of time than foreground tasks and generally remain invisible to the user unless the user requests an update or brings the task to the foreground. Generally, only multitasking operating systems are able to support background processing. However, some operating systems that do not support multitasking may be able to perform one or more types of background tasks. For example, in the Apple Macintosh operating system running with multitasking turned off, the Background Printing option can be used to print documents while the user is doing other work. See also multitasking. Compare foreground1.

background2: n. 1. The color against which characters and graphics are displayed, such as a white background for black characters. Compare foreground2 (definition 1). 2. The colors, textures, patterns, and pictures that comprise the surface of the desktop, upon which icons, buttons, menu bars, and toolbars are situated. See also wallpaper (definition 1). 3. The colors, textures, patterns, and pictures that comprise the surface of a Web page, upon which text, icons, graphics, buttons, and other items are situated. See also wallpaper (definition 2). 4. The condition of an open but currently inactive window in a windowing environment. See also inactive window. Compare foreground2 (definition 2).

background noise: n. The noise inherent in a line or circuit, independent of the presence of a signal. See also noise.

background printing: n. The process of sending a document to a printer at the same time that the computer is performing one or more tasks.

background processing: n. The execution of certain operations by the operating system or a program during momentary lulls in the primary (foreground) task. An example of a background process is a word processor program printing a document during the time between the user's keystrokes. See also background1.

back-lit display: n. An LCD display that uses a light source behind the screen to enhance image sharpness and readability, especially in environments that are brightly lit.

backslash: n. The character (\) used to separate directory names in MS-DOS path specifications. When used as a leading character, it means that the path specification begins from the topmost level for that disk drive. See also path.

Backspace key: n. 1. A key that, on IBM and compatible keyboards, moves the cursor to the left, one character at a time, usually erasing each character as it moves. 2. On Macintosh keyboards, a key (called the Delete key on some Macintosh keyboards) that erases currently selected text or, if no text is selected, erases the character to the left of the insertion point (cursor).

backup: n. A duplicate copy of a program, a disk, or data, made either for archiving purposes or for safeguarding valuable files from loss should the active copy be damaged or destroyed. A backup is an "insurance" copy. Some application programs automatically make backup copies of data files, maintaining both the current version and the preceding version on disk. Also called backup copy, backup file.

backup and restore: n. The process of maintaining backup files and putting them back onto the source medium if necessary.

bad sector: n. A disk sector that cannot be used for data storage, usually because of media damage or imperfections. Finding, marking, and avoiding bad sectors on a disk is one of the many tasks performed by a computer's operating system. A disk-formatting utility can also find and mark the bad sectors on a disk.

balloon help: n. In the Mac OS 7.x, an on-screen help feature in the form of a cartoon dialog balloon. After activating this feature by clicking on the ballon icon on the toolbar, the user can position the cursor over an icon or other item, and a dialog balloon will appear that describes the function of the item.

band: n. 1. In printing graphics, a rectangular portion of a graphic sent by the computer to a printer. The technique of dividing a graphic into bands prevents a printer from having to reconstruct an entire image in memory before printing it. 2. In communications, a contiguous range of frequencies used for a particular purpose, such as radio or television broadcasts.

bandwidth: n. 1. The difference between the highest and lowest frequencies that an analog communications system can pass. For example, a telephone accommodates a bandwidth of 3,000 Hz: the difference between the lowest (300 Hz) and highest (3,300 Hz) frequencies it can carry. 2. The data transfer capacity of a digital communications system.

bank: n. 1. Any group of similar electrical devices connected together for use as a single device. For example, transistors may be connected in a row/column array inside a chip to form memory, or several memory chips may be connected together to form a memory module such as a SIMM. See also SIMM. 2. A section of memory, usually of a size convenient for a CPU to address. For example, an 8-bit processor can address 65,536 bytes of memory; therefore, a 64-kilobyte (64-KB) memory bank is the largest that the processor can address at once. To address another 64-KB bank of memory requires circuitry that fools the CPU into looking at a separate block of memory. See also bank switching, page (definition 2).

bank switching: n. A method of expanding a computer's available random access memory (RAM) by switching between banks of RAM chips that share a range of memory addresses, which is set aside before switching begins. Only one bank is directly accessible at a time; when a bank is not active, it retains whatever is stored in it. Before another bank can be used, the operating system, driver, or program must explicitly issue a command to the hardware to make the switch. Because switching between banks takes time, memory-intensive operations take longer with bank-switched memory than with main memory. Bank-switched memory typically takes the form of an expansion card that plugs into a slot on the motherboard.

banner: n. A section of a Web page containing an advertisement that is usually an inch or less tall and spans the width of the Web page. The banner contains a link to the advertiser's own Web site. See also Web page, Web site.

banner page: n. 1. The title page that may be added to printouts by most print spoolers. Such a page typically incorporates account ID information, job length, and print spooler information, and is used primarily to separate one print job from another. See also print spooler. 2. In software, an initial screen used to identify a product and credit its producers.

bar chart: n. A type of graphic in which data items are shown as rectangular bars. The bars may be displayed either vertically or horizontally and may be distinguished from one another by color or by some type of shading or pattern. Positive and negative values may be shown in relation to a zero baseline. Two types of bar charts are common: a standard bar chart, in which each value is represented by a separate bar, and a stacked bar chart, in which several data points are "stacked" to produce a single bar. Also called bar graph.

bar code: n. The special identification code printed as a set of vertical bars of differing widths on books, grocery products, and other merchandise. Used for rapid, error-free input in such facilities as libraries, hospitals, and grocery stores, bar codes represent binary information that can be read by an optical scanner. The coding can include numbers, letters, or a combination of the two; some codes include built-in error checking and can be read in either direction.

bare bones2: n. 1. An application that provides only the most basic functions necessary to perform a given task. 2. A computer consisting only of motherboard (equipped with CPU and RAM), cabinet, power supply, floppy disk drive, and keyboard, to which the user must add hard disk, video adapter, monitor, and any other peripherals. See also motherboard, peripheral.

base address: n. The part of a two-part memory address that remains constant and provides a reference point from which the location of a byte of data can be calculated. A base address is accompanied by an offset value that is added to the base to determine the exact location (the absolute address) of the information. The concept is similar to a street address system. For example, "2010 Main Street" consists of a base (the 2000 block of Main Street) plus an offset (10 from the beginning of the block). Base addresses are known as segment addresses in IBM PCs and compatibles; data in these computers is identified by its position as a relative offset from the start of the segment. See also absolute address, offset, relative address, segment.

baseband: adj. Of or relating to communications systems in which the medium of transmission (such as a wire or fiber-optic cable) carries a single message at a time in digital form. Baseband communication is found in local area networks such as Ethernet and Token Ring. See also Ethernet, fiber optics, Token Ring network. Compare broadband.

baseband network: n. A type of local area network in which messages travel in digital form on a single transmission channel between machines connected by coaxial cable or twisted-pair wiring. Machines on a baseband network transmit only when the channel is not busy, although a technique called time-division multiplexing can enable channel sharing. Each message on a baseband network travels as a packet that contains information about the source and destination machines as well as message data. Baseband networks operate over short distances at speeds ranging from about 50 kilobits per second (50 Kbps) to 16 megabits per second (16 Mbps). Receiving, verifying, and converting a message, however, add considerably to the actual time, reducing throughput. The maximum recommended distance for such a network is about 2 miles, or considerably less if the network is heavily used. See also coaxial cable, multiplexing, packet, throughput, time-division multiplexing, twisted-pair cable. Compare broadband network.

baseline: n. In the printing and display of characters on the screen, an imaginary horizontal line with which the base of each character, excluding descenders, is aligned. See also ascender, descender, font.

base URL: n. A uniform resource locator (URL) that you can optionally assign to a page to convert relative URLs on that page into absolute URLs. A base URL should end with a document name or a trailing slash. See also absolute URL.

Basic or BASIC: n. Acronym for Beginner's All-purpose Symbolic Instruction Code, a high-level programming language developed in the mid-1960s by John Kemeny and Thomas Kurtz at Dartmouth College. It is widely considered one of the easiest programming languages to learn. See also True Basic, Visual Basic.

batch: n. A group of documents or data records that are processed as a unit. See also batch job, batch processing.

batch file: n. An ASCII text file containing a sequence of operating-system commands, possibly including parameters and operators supported by the batch command language. When the user types a batch filename at the command prompt, the commands are processed sequentially. Also called batch program. See also AUTOEXEC.BAT, .bat.

batch job: n. A program or set of commands that runs without user interaction. See also batch processing.

batch processing: n. 1. Execution of a batch file. See also batch file. 2. The practice of acquiring programs and data sets from users, running them one or a few at a time, and then providing the results to the users. 3. The practice of storing transactions for a period of time before they are posted to a master file, typically in a separate operation undertaken at night. Compare transaction processing.

batch program: n. A program that executes without interacting with the user. See also batch file. Compare interactive program.

battery: n. Two or more cells in a container that produces an electrical current when two electrodes within the container touch an electrolyte. In personal computers, batteries are used as an auxiliary source of power when the main power is shut off, as a power source for laptop and notebook computers (rechargeable batteries, such as nickel cadmium, nickel metal hydride, and lithium ion, are used), and as a method to keep the internal clock and the circuitry responsible for the part of RAM that stores important system information always powered up. See also lead ion battery, lithium ion battery, nickel cadmium battery, nickel metal hydride battery, RAM.

battery backup: n. 1. A battery-operated power supply used as an auxiliary source of electricity in the event of a power failure. 2. Any use of a battery to keep a circuit running when the main power is shut off, such as powering a computer's clock/calendar and the special RAM that stores important system information between sessions. See also UPS.

baud: n. One signal change per second, a measure of data transmission speed. Named after the French engineer and telegrapher Jean-Maurice-Emile Baudot and originally used to measure the transmission speed of telegraph equipment, the term now most commonly refers to the data transmission speed of a modem. See also baud rate.

baud rate: n. The speed at which a modem can transmit data. The baud rate is the number of events, or signal changes, that occur in one second--not the number of bits per second (bps) transmitted. In high-speed digital communications, one event can actually encode more than one bit, and modems are more accurately described in terms of bits per second than baud rate. For example, a so-called 9,600-baud modem actually operates at 2,400 baud but transmits 9,600 bits per second by encoding 4 bits per event (2,400 × 4 = 9,600) and thus is a 9,600-bps modem. Compare bit rate, transfer rate.

bay: n. A shelf or opening used for the installation of electronic equipment--for example, the space reserved for additional disk drives, CD-ROM drives, or other equipment in the cabinets of microcomputers. See also drive bay.

BBS: n. 1. Acronym for bulletin board system. A computer system equipped with one or more modems or other means of network access that serves as an information and message-passing center for remote users. Often BBSs are focused on special interests, such as science fiction, movies, Windows software, or Macintosh systems, and can have free or fee-based access, or a combination. Users dial into a BBS with their modems and post messages to other BBS users in special areas devoted to a particular topic, in a manner reminiscent of the posting of notes on a cork bulletin board. Many BBSs also allow users to chat online with other users, send e-mail, download and upload files that include freeware and shareware software, and access the Internet. Many software and hardware companies run proprietary BBSs for customers that include sales information, technical support, and software upgrades and patches. 2. Acronym for be back soon. A shorthand expression often seen in Internet discussion groups by a participant leaving the group who wishes to bid a temporary farewell to the rest of the group.

bcc: n. Acronym for blind courtesy copy. A feature of e-mail programs that allows a user to send a copy of an e-mail message to a recipient without notifying other recipients that this was done. Generally, the recipient's address is entered into a field called "bcc:" in the mail header. Also called blind carbon copy. See also e-mail, header (definition 1). Compare cc.

bearer channel: n. One of the 64-Kbps communications channels on an ISDN circuit. A BRI (Basic Rate Interface) ISDN line has 2 bearer channels and 1 data channel. A PRI (Primary Rate Interface) ISDN line has 23 bearer channels (in North America) or 30 bearer channels (in Europe) and 1 data channel. See also BRI, channel (definition 2), ISDN.

bells and whistles: n. Attractive features added to hardware or software beyond basic functionality, comparable to accessories, such as electric door locks and air conditioning, added to an automobile. Products, especially computer systems, without such adornments are sometimes called "plain vanilla."

benchmark1: n. A test used to measure hardware or software performance. Benchmarks for hardware use programs that test the capabilities of the equipment--for example, the speed at which a CPU can execute instructions or handle floating-point numbers. Benchmarks for software determine the efficiency, accuracy, or speed of a program in performing a particular task, such as recalculating data in a spreadsheet. The same data is used with each program tested, so the resulting scores can be compared to see which programs perform well and in what areas. The design of fair benchmarks is something of an art, because various combinations of hardware and software can exhibit widely variable performance under different conditions. Often, after a benchmark has become a standard, developers try to optimize a product to run that benchmark faster than similar products run it in order to enhance sales. See also sieve of Eratosthenes.

benchmark2: vb. To measure the performance of hardware or software.

benign virus: n. A program that exhibits properties of a virus, such as self-replication, but does not otherwise do harm to the computer systems that it infects.

best of breed: adj. A term used to describe a product that is the best in a particular category of products.

beta1: adj. Of or relating to software or hardware that is a beta. See also beta2. Compare alpha1.

beta2: n. A new software or hardware product, or one that is being updated, that is ready to be released to users for beta testing. See also beta test.

beta site: n. An individual or an organization that tests software before it is released to the public. The company producing the software usually selects these beta sites from a pool of established customers or volunteers. Most beta sites perform this service free of charge, often to get a first look at the software and to receive free copies of the software once it is released to the public.

beta test: n. A test of software that is still under development, accomplished by having people actually use the software. In a beta test, a software product is sent to selected potential customers and influential end users (known as beta sites), who test its functionality and report any operational or utilization errors (bugs) found. The beta test is usually one of the last steps a software developer takes before releasing the product to market; however, if the beta sites indicate that the software has operational difficulties or an extraordinary number of bugs, the developer may conduct more beta tests before the software is released to customers.

Bézier curve: n. A curve that is calculated mathematically to connect separate points into smooth, free-form curves and surfaces of the type needed for illustration programs and CAD models. Bézier curves need only a few points to define a large number of shapes--hence their usefulness over other mathematical methods for approximating a given shape. See also CAD.

bias: n. 1. A uniform or systematic deviation from a point of reference. 2. In mathematics, an indication of the amount by which the average of a group of values deviates from a reference value. 3. In electronics, a voltage applied to a transistor or other electronic device to establish a reference level for its operation. 4. In communications, a type of distortion in the length of transmitted bits, caused by a lag that occurs as voltage builds up or falls off each time the signal changes from 0 to 1 or vice versa.

bidirectional: adj. Operating in two directions. A bidirectional printer can print from left to right and from right to left; a bidirectional bus can transfer signals in both directions between two devices.

bidirectional parallel port: n. An interface that supports two-way parallel communication between a device and a computer.

bidirectional printing: n. The ability of an impact or ink-jet printer to print from left to right and from right to left. Bidirectional printing improves speed substantially because no time is wasted returning the print head to the beginning of the next line, but it may lower print quality.

Big Blue: n. The International Business Machines (IBM) Corporation. This nickname comes from the corporate color used on IBM's early mainframes and still used in the company logo.

binary1: adj. Having two components, alternatives, or outcomes. The binary number system has 2 as its base, so values are expressed as combinations of two digits, 0 and 1. These two digits can represent the logical values true and false as well as numerals, and they can be represented in an electronic device by the two states on and off, recognized as two voltage levels. Therefore, the binary number system is at the heart of digital computing. Although ideal for computers, binary numbers are usually difficult for people to interpret because they are repetitive strings of 1s and 0s. To ease translation, programmers and others who habitually work with the computer's internal processing abilities use hexadecimal (base-16) or octal (base-8) numbers. Equivalents and conversion tables for binary, decimal, hexadecimal, and octal are in Appendix E. See also base, binary-coded decimal, binary number, bit, Boolean algebra, byte, cyclic binary code, digital computer, dyadic, logic circuit. Compare ASCII, decimal, hexadecimal, octal.

binary2: n. In an FTP client program, the command that instructs the FTP server to send or receive files as binary data. See also FTP client, FTP server. Compare ASCII.

binary digit: n. Either of the two digits in the binary number system, 0 and 1. See also bit.

binary file: n. A file consisting of a sequence of 8-bit data or executable code, as distinguished from files consisting of human-readable ASCII text. Binary files are usually in a form readable only by a program, often compressed or structured in a way that is easy for a particular program to read. Compare ASCII file.

binary file transfer: n. Transfer of a file containing arbitrary bytes or words, as opposed to a text file containing only printable characters (for example, ASCII characters with codes 10, 13, and 32-126). On modern operating systems a text file is simply a binary file that happens to contain only printable characters, but some older systems distinguish the two file types, requiring programs to handle them differently. Acronym: BFT.

binary format: n. Any format that structures data in 8-bit form. Binary format is generally used to represent object code (program instructions translated into a machine-readable form) or data in a transmission stream. See also binary file.

binary notation: n. Representation of numbers using the binary digits, 0 and 1. Compare floating-point notation.

binary number: n. A number expressed in binary form. Because binary numbers are based on powers of 2, they can be interpreted as follows: See also binary1. k:\compdict\database\8780.doc

binary search: n. A type of search algorithm that seeks an item, with a known name, in an ordered list by first comparing the sought item to the item at the middle of the list's order. The search then divides the list in two, determines in which half of the order the item should be, and repeats this process until the sought item is found. Also called binary chop, dichotomizing search. See also search algorithm. Compare hash search, linear search.

binary transfer: n. The preferred mode of electronic exchange for executable files, application data files, and encrypted files. Compare ASCII transfer.

binary tree:
n. In programming, a specific type of tree data structure in which each node has at most two subtrees, one left and one right. Binary trees are often used for sorting information; each node of the binary search tree contains a key, with values less than that key added to one subtree and values greater than that key added to the other. See also binary search, tree.

bind: vb. To associate two pieces of information with one another. The term is most often used with reference to associating a symbol (such as the name of a variable) with some descriptive information (such as a memory address, a data type, or an actual value). See also binding time, dynamic binding, static binding.

BinHex1: n. 1. A code for converting binary data files into ASCII text so they can be transmitted via e-mail to another computer or in a newsgroup post. This method can be used when standard ASCII characters are needed for transmission, as they are on the Internet. BinHex is used most frequently by Mac users. See also MIME. 2. An Apple Macintosh program for converting binary data files into ASCII text and vice versa using the BinHex code. Compare uudecode1, uuencode1.

BinHex2: vb. To convert a binary file into printable 7-bit ASCII text or to convert the resulting ASCII text file back to binary format using the BinHex program. Compare uudecode2, uuencode2.

BIOS: n. Acronym for basic input/output system. On PC-compatible computers, the set of essential software routines that test hardware at startup, start the operating system, and support the transfer of data among hardware devices. The BIOS is stored in read-only memory (ROM) so that it can be executed when the computer is turned on. Although critical to performance, the BIOS is usually invisible to computer users. See also AMI BIOS, CMOS setup, Phoenix BIOS, ROM BIOS. Compare Toolbox.

bit: n. Short for binary digit. The smallest unit of information handled by a computer. One bit expresses a 1 or a 0 in a binary numeral, or a true or false logical condition, and is represented physically by an element such as a high or low voltage at one point in a circuit or a small spot on a disk magnetized one way or the other. A single bit conveys little information a human would consider meaningful. A group of 8 bits, however, makes up a byte, which can be used to represent many types of information, such as a letter of the alphabet, a decimal digit, or other character. See also ASCII, binary, byte.

bit bucket: n. An imaginary location into which data can be discarded. A bit bucket is a null input/output device from which no data is read and to which data can be written without effect. The NUL device recognized by MS-DOS is a bit bucket. A directory listing, for example, simply disappears when sent to NUL.

bit flipping: n. A process of inverting bits--changing 1s to 0s and vice versa. For example, in a graphics program, to invert a black-and-white bitmapped image (to change black to white and vice versa), the program could simply flip the bits that compose the bit map.

bit image: n. A sequential collection of bits that represents in memory an image to be displayed on the screen, particularly in systems having a graphical user interface. Each bit in a bit image corresponds to one pixel (dot) on the screen. The screen itself, for example, represents a single bit image; similarly, the dot patterns for all the characters in a font represent a bit image of the font. In a black-and-white display each pixel is either white or black, so it can be represented by a single bit. The "pattern" of 0s and 1s in the bit image then determines the pattern of white and black dots forming an image on the screen. In a color display the corresponding description of on-screen bits is called a pixel image because more than one bit is needed to represent each pixel. See also bit map, pixel image.

bit map or bitmap: n. A data structure in memory that represents information in the form of a collection of individual bits. A bit map is used to represent a bit image. Another use of a bit map in some systems is the representation of the blocks of storage on a disk, indicating whether each block is free (0) or in use (1). See also bit image, pixel image.

bitmapped font: n. A set of characters in a particular size and style in which each character is described as a unique bit map (pattern of dots). Macintosh screen fonts are examples of bitmapped fonts. See also downloadable font, outline font, TrueType. Compare PostScript font, vector font.

bitmapped graphics: n. Computer graphics represented as arrays of bits in memory that represent the attributes of the individual pixels in an image (one bit per pixel in a black-and-white display, multiple bits per pixel in a color or gray-scale display). Bitmapped graphics are typical of paint programs, which treat images as collections of dots rather than as shapes. See also bit image, bit map, pixel image. Compare object-oriented graphics.

BITNET: n. Acronym for Because It's Time Network. A wide area network, founded in 1981 and operated by the Corporation for Research and Educational Networking (CREN) in Washington, D.C., used to provide e-mail and file transfer services between mainframe computers at educational and research institutions in North America, Europe, and Japan. BITNET uses the IBM Network Job Entry (NJE) protocol rather than TCP/IP, but it can exchange e-mail with the Internet. The listserv software for maintaining mailing lists was originated on BITNET.

bit. newsgroups: n. A hierarchy of Internet newsgroups that mirror the content of some BITNET mailing lists. See also BITNET.

bit pattern: n. 1. A combination of bits, often used to indicate the possible unique combinations of a specific number of bits. For example, a 3-bit pattern allows 8 possible combinations and an 8-bit pattern allows 256 combinations. 2. A pattern of black and white pixels in a computer system capable of supporting bitmapped graphics. See also pixel.

bits per inch: n. A measure of data storage capacity; the number of bits that fit into an inch of space on a disk or a tape. On a disk, bits per inch are measured based on inches of circumference of a given track. See also packing density. Acronym: BPI.

bit stream: n. 1. A series of binary digits representing a flow of information transferred through a given medium. 2. In synchronous communications, a continuous flow of data in which characters in the stream are separated from one another by the receiving station rather than by markers, such as start and stop bits, inserted into the data.

bit stuffing: n. The practice of inserting extra bits into a stream of transmitted data. Bit stuffing is used to ensure that a special sequence of bits appears only at desired locations. For example, in the HDLC, SDLC, and X.25 communications protocols, six 1 bits in a row can appear only at the beginning and end of a frame (block) of data, so bit stuffing is used to insert a 0 bit into the rest of the stream whenever five 1 bits appear in a row. The inserted 0 bits are removed by the receiving station to return the data to its original form. See also HDLC, SDLC, X.25.

BIX: n. Acronym for BYTE Information Exchange. An online service originated by BYTE magazine, now owned and operated by Delphi Internet Services Corporation. BIX offers e-mail, software downloads, and conferences relating to hardware and software.

black box: n. A unit of hardware or software whose internal structure is unknown but whose function is documented. The internal mechanics of the function do not matter to a designer who uses a black box to obtain that function. For example, a memory chip can be viewed as a black box. Many people use memory chips and design them into computers, but generally only memory chip designers need to understand their internal operation.

blackout: n. A condition in which the electricity level drops to zero; a complete loss of power. A number of factors cause a blackout, including natural disasters, such as a storm or an earthquake, or a failure in the power company's equipment, such as a transformer or a power line. A blackout might or might not damage a computer, depending on the state of the computer when the blackout occurs. As with switching a computer off before saving any data, a blackout will cause all unsaved data to be irretrievably lost. The most potentially damaging situation is one in which a blackout occurs while a disk drive is reading information from or writing information to a disk. The information being read or written will probably become corrupted, causing the loss of a small part of a file, an entire file, or the entire disk; the disk drive itself might suffer damage as a result of the sudden power loss. The only reliable means of preventing damage caused by a blackout is to use a battery-backed uninterruptible power supply (UPS). See also UPS. Compare brownout.

blank1: n. The character entered by pressing the spacebar. See also space character.

blank2: vb. To not show or not display an image on part or all of the screen.

bleed: n. In a printed document, any element that runs off the edge of the page or into the gutter. Bleeds are often used in books to mark important pages so they are easier to find. See also gutter.

blink: vb. To flash on and off. Cursors, insertion points, menu choices, warning messages, and other displays on a computer screen that are intended to catch the eye are often made to blink. The rate of blinking in a graphical user interface can sometimes be controlled by the user.

block1: n. 1. Generally, a contiguous collection of similar things that are handled together as a whole. 2. A section of random access memory temporarily assigned (allocated) to a program by the operating system. 3. A group of statements in a program that are treated as a unit. For example, if a stated condition is true, all of the statements in the block are executed, but none are executed if the condition is false. 4. A unit of transmitted information consisting of identification codes, data, and error-checking codes. 5. A collection of consecutive bytes of data that are read from or written to a device (such as a disk) as a group. 6. A rectangular grid of pixels that are handled as a unit. 7. A segment of text that can be selected and acted upon as a whole in an application.

block2: vb. 1. To distribute a file over fixed-size blocks in storage. 2. To prevent a signal from being transmitted. 3. To select a segment of text, by using a mouse, menu selection, or cursor key, to be acted upon in some way, such as to format or to delete the segment.

block cursor: n. An on-screen cursor that has the same width and height in pixels as a text-mode character cell. A block cursor is used in text-based applications, especially as the mouse pointer when a mouse is installed in the system. See also character cell, cursor (definition 1), mouse pointer.

block diagram: n. A chart of a computer or other system in which labeled blocks represent principal components and lines and arrows between the blocks show the pathways and relationships among the components. A block diagram is an overall view of what a system consists of and how it works. To show the various components of such a system in more detail, different types of diagrams, such as flowcharts or schematics, are used. Compare bubble chart, flowchart.

blue screen: n. A technique used in film matte special effects, in which one image is superimposed on another image. Action or objects are filmed against a blue screen. The desired background is filmed separately, and the shot containing the action or objects is superimposed onto the background. The result is one image where the blue screen disappears.

BNC connector: n. A connector for coaxial cables that locks when one connector is inserted into another and rotated 90 degrees. BNC connectors are often used with closed-circuit television. See also coaxial cable.

board: n. An electronic module consisting of chips and other electronic components mounted on a flat, rigid substrate on which conductive paths are laid between the components. A personal computer contains a main board, called the motherboard, which usually has the microprocessor on it and slots into which other, smaller boards, called cards or adapters, can be plugged to expand the functionality of the main system, such as to connect to monitors, disk drives, or a network. See also adapter, card (definition 1), motherboard.

body: n. In e-mail and Internet newsgroups, the content of a message. The body of a message follows the header, which contains information about the sender, origin, and destination of the message. See also header (definition 1).

body face: n. A typeface suitable for the main text in a document rather than for headings and titles. Because of their readability, fonts having serifs, such as Times and Palatino, are good body faces, although sans serif faces can also be used as body text. See also sans serif, serif. Compare display face.

boilerplate: n. Recyclable text; a piece of writing or code, such as an organization's mission statement or the graphics code that prints a software company's logo, which can be used over and over in many different documents. The size of boilerplate text can range from a paragraph or two to many pages. It is, essentially, generic composition that can be written once, saved on disk, and merged, either verbatim or with slight modification, into whatever documents or programs later require it.

boldface: n. A type style that makes the text to which it is applied appear darker and heavier than the surrounding text. Some applications allow the user to apply a "Bold" command to selected text; other programs require that special codes be embedded in the text before and after words that are to be printed in boldface. This sentence appears in boldface.

bomb1: n. A program planted surreptitiously, with intent to damage or destroy a system in some way--for example, to erase a hard disk or cause it to be unreadable to the operating system. See also Trojan horse, virus, worm.

bomb2: vb. To fail abruptly and completely, without giving the user a chance to recover from the problem short of restarting the program or system. See also abend, bug (definition 1), crash3 (definition 1), hang.

bookmark: n. 1. A marker inserted at a specific point in a document to which the user may wish to return for later reference. 2. A named location on a page that can be the target of a hyperlink. A bookmark can be applied to a set of characters or it can exist on a page separately from any text.

bookmark file: n. 1. A Netscape Navigator file containing the addresses of preferred Web sites. It is synonymous with the Favorites folder in Internet Explorer and the hotlist in Mosaic. See also Favorites folder, hotlist, Internet Explorer, Mosaic. 2. A rendering of such a file in HTML format, generally posted on a Web page for the benefit of other people. See also HTML.

Boolean: adj. Of, pertaining to, or characteristic of logical (true, false) values. Many languages directly support a Boolean data type, with predefined values for true and false; others use integer data types to implement Boolean values, usually (although not always) with 0 equaling false and "not 0" equaling true. See also Boolean algebra, Boolean operator.

Boolean search: n. A database search that uses Boolean operators. See also Boolean operator.

boot1: n. The process of starting or resetting a computer. When first turned on (cold boot) or reset (warm boot), the computer executes the software that loads and starts the computer's more complicated operating system and prepares it for use. Thus, the computer can be said to pull itself up by its own bootstraps. Also called bootstrap. See also BIOS, bootstrap loader, cold boot, warm boot.

boot2: vb. 1. To start or reset a computer by turning the power on, by pressing a reset button on the computer case, or by issuing a software command to restart. Also called bootstrap, boot up. See also reboot. 2. To execute the bootstrap loader program. Also called bootstrap. See also bootstrap loader.

bootable: adj. Containing the system files necessary for booting a PC and running it. See also boot2.

boot disk: n. A floppy disk that contains key system files from a PC-compatible operating system and that can boot, or start, the PC. A boot disk must be inserted in the primary floppy disk drive (usually drive A:) and is used when there is some problem with starting the PC from the hard disk, from which the computer generally boots. Also called bootable disk. See also A:, boot2, boot drive, hard disk.

boot drive: n. In a PC-compatible computer, the disk drive that the BIOS uses to automatically load the operating system when the computer is turned on. Generally, the default boot drive is the primary floppy disk drive A: in PC-compatible computers with MS-DOS, Windows 3.x, or Windows 95 operating systems. If a floppy disk is not found in that drive, the BIOS will check the primary hard disk next, which is drive C:. The BIOS for these operating systems can be reconfigured to search drive C: first by using the BIOS setup program. See also A:, BIOS, disk drive, hard disk.

boot failure: n. The inability of a computer to locate or activate the operating system and thus boot, or start, the computer. See also boot2.

boot partition: n. The partition on a hard disk that contains the operating system and support files that the system loads into memory when the computer is turned on or restarted.

Boot Protocol: n. A protocol described in RFCs 951 and 1084 and used for booting diskless workstations. Also called BOOTP. See also boot2, RFC.

boot record: n. The section of a disk that contains the operating system.

boot sector: n. The portion of a disk reserved for the bootstrap loader (the self-starting portion) of an operating system. The boot sector typically contains a short machine language program that loads the operating system.

bootstrap loader: n. A program that is automatically run when a computer is switched on (booted). After first performing a few basic hardware tests, the bootstrap loader loads and passes control to a larger loader program, which typically then loads the operating system. The bootstrap loader typically resides in the computer's read-only memory (ROM).

border: n. 1. In programs and working environments that feature on-screen windows, the edge surrounding the user's workspace. Window borders provide a visible frame around a document or graphic. Depending on the program and its requirements, they can also represent an area in which the cursor or a mouse pointer takes on special characteristics. For example, clicking the mouse on a window border can enable the user to resize the window or split the window in two. 2. In printing, a decorative line or pattern along one or more edges of a page or illustration.

Border Gateway Protocol: n. A protocol used by NSFnet that is based on the External Gateway Protocol. See also External Gateway Protocol, NSFnet. Acronym: BGP.

BounceKeys: n. A feature in Windows 95 that instructs the processor to ignore double strokes of the same key and other unintentional keystrokes.

bound1: adj. Limited in performance or speed; for example, an input/output-bound system is limited by the speed of its input and output devices (keyboard, disk drives, and so on), even though the processor or program is capable of performing at a higher rate.

bound2: n. The upper or lower limit in a permitted range of values.

bozo filter: n. On the Internet, slang for a feature in some e-mail clients and newsgroup readers or a separate utility that allows the user to block, or filter out, incoming e-mail messages or newsgroup articles from specified individuals. Generally these individuals are ones that the user does not want to hear from, such as bozos. Also called kill file. See also bozo.

bps: n. Short for bits per second. The speed at which a device such as a modem can transfer data. Speed in bps is not the same as baud rate. See also baud, baud rate.

brain dump: n. A large, unorganized mass of information, presented in response to a query via e-mail or a newsgroup article, that is difficult to digest or interpret.

branch: n. 1. A node intermediate between the root and the leaves in some types of logical tree structure, such as the directory tree in Windows or a tape distribution organization. 2. Any connection between two items such as blocks in a flowchart or nodes in a network. See branch instruction.

BRB: Acronym for (I'll) be right back. An expression used commonly on live chat services on the Internet and online information services by participants signaling their temporary departure from the group. See also chat (definition 1).

break1: n. 1. Interruption of a program caused by the user pressing the Break key or its equivalent. 2. Interruption of a communications transmission that occurs when the receiving station interrupts and takes over control of the line or when the transmitting station prematurely halts transmission.

break2: vb. 1. To interrupt execution at a given spot, usually for the purpose of debugging. See also breakpoint. 2. To cause a routine, module, or program that had previously worked to cease working correctly.

Break key: n. A key or combination of keys used to tell a computer to halt, or break out of, whatever it is doing. On IBM PCs and compatibles under DOS, pressing the Pause/Break or Scroll Lock/Break key while holding down the Ctrl key issues the break command (as does Ctrl-C). On Macintosh computers, the key combination that sends a break code is Command-period.

breakpoint: n. A location in a program at which execution is halted so that a programmer can examine the program's status, the contents of variables, and so on. A breakpoint is set and used within a debugger and is usually implemented by inserting at that point some kind of jump, call, or trap instruction that transfers control to the debugger. See also debug, debugger.

BRI: n. Acronym for Basic Rate Interface. An ISDN subscriber service that uses two B (64 Kbps) channels and one D (64 Kbps) channel to transmit voice, video, and data signals. See also ISDN.

bridge: n. 1. A device that connects networks using the same communications protocols so that information can be passed from one to the other. Compare gateway. 2. A device that connects two local area networks, whether or not they use the same protocols. A bridge operates at the ISO/OSI data-link layer. See also data-link layer. Compare router.

bridge router: n. A device that supports the functions of both a bridge and router. A bridge router links two segments of a local or wide area network, passing packets of data between the segments as necessary, and uses Level 2 addresses for routing. Also called Brouter. See also bridge (definition 2), router.

Briefcase: n. A system folder in Windows 95 used for synchronizing files between two computers, usually between desktop and laptop computers. The Briefcase can be transferred to another computer via disk, cable, or network. When files are transferred back to the original computer, the Briefcase updates all files to the most recent version.

brightness: n. The perceived quality of radiance or luminosity of a visible object. Brightness is literally in the eye (and mind) of the beholder; a candle in the night appears brighter than the same candle under incandescent lights. Although its subjective value cannot be measured with physical instruments, brightness can be measured as luminance (radiant energy). The brightness component of a color is different from its color (the hue) and from the intensity of its color (the saturation). See also color model, HSB.

broadband: adj. Of or relating to communications systems in which the medium of transmission (such as a wire or fiber-optic cable) carries multiple messages at a time, each message modulated on its own carrier frequency by means of modems. Broadband communication is found in wide area networks. Compare baseband.

broadband network: n. A local area network on which transmissions travel as radio-frequency signals over separate inbound and outbound channels. Stations on a broadband network are connected by coaxial or fiber-optic cable, which can carry data, voice, and video simultaneously over multiple transmission channels that are distinguished by frequency. A broadband network is capable of high-speed operation (20 megabits or more), but it is more expensive than a baseband network and can be difficult to install. Such a network is based on the same technology used by cable television (CATV). Also called wideband transmission. Compare baseband network.

broadcast1: adj. Sent to more than one recipient. In communications and on networks, a broadcast message is one distributed to all stations. See also e-mail.

broadcast2: n. As in radio or television, a transmission sent to more than one recipient.

brownout: n. A condition in which the electricity level is appreciably reduced for a sustained period of time. In contrast to a blackout, or total loss of power, a brownout continues the flow of electricity to all devices connected to electrical outlets, although at lower levels than the normally supplied levels (120 volts in the United States). A brownout can be extremely damaging to sensitive electronic devices, such as computers, because the reduced and often fluctuating voltage levels can cause components to operate for extended periods of time outside the range they were designed to work in. On a computer, a brownout is characterized by a smaller, dimmer, and somewhat fluctuating display area on the monitor and potentially erratic behavior by the system unit. The only reliable means of preventing damage caused by a brownout condition is to use a battery-backed uninterruptible power supply (UPS). See also UPS. Compare blackout.

browse: vb. To scan a database, a list of files, or the Internet, either for a particular item or for anything that seems to be of interest. Generally, browsing implies observing, rather than changing, information. In unauthorized computer hacking, browsing is a (presumably) nondestructive means of finding out about an unknown computer after illegally gaining entry.

brush: n. A tool used in paint programs to sketch or fill in areas of a drawing with the color and pattern currently in use. Paint programs that offer a variety of brush shapes can produce brushstrokes of varying width and, in some cases, shadowing or calligraphic effects.

BSD UNIX: n. Acronym for Berkeley Software Distribution UNIX. A UNIX version developed at the University of California at Berkeley, providing additional capabilities such as networking, extra peripheral support, and use of extended filenames. BSD UNIX was instrumental in gaining widespread acceptance of UNIX and in getting academic institutions connected to the Internet. BSD UNIX is now being developed by Berkeley Software Design, Inc. See also UNIX.

B-tree: n. A tree structure for storing database indexes. Each node in the tree contains a sorted list of key values and links that correspond to ranges of key values between the listed values. To find a specific data record given its key value, the program reads the first node, or root, from the disk and compares the desired key with the keys in the node to select a subrange of key values to search. It repeats the process with the node indicated by the corresponding link. At the lowest level, the links indicate the data records. The database system can thus rapidly skip down through the levels of the tree structure to find the simple index entries that contain the location of the desired records or rows.

BTW or btw: Acronym for by the way. An expression often used to preface remarks in e-mail and Internet newsgroup articles.

bubble chart: n. A chart in which annotated ovals (bubbles) representing categories, operations, or procedures are connected by lines or arrows that represent data flows or other relationships among the items represented by bubbles. In systems analysis, bubble charts, rather than block diagrams or flowcharts, are used to describe the connections between concepts or parts of a whole, without emphasizing a structural, sequential, or procedural relationship between the parts. Compare block diagram, flowchart.

bubble-jet printer: n. A form of nonimpact printer that uses a mechanism similar to that used by an ink-jet printer to shoot ink from nozzles to form characters on paper. A bubble-jet printer uses special heating elements to prepare the ink, whereas an ink-jet printer uses piezoelectric crystals. See also ink-jet printer, nonimpact printer. Compare laser printer.

bucket: n. A region of memory that is addressable as an entity and can be used as a receptacle to hold data. See also bit bucket.

buffer1: n. A region of memory reserved for use as an intermediate repository in which data is temporarily held while waiting to be transferred between two locations, as between an application's data area and an input/output device. A device or its adapter may in turn use a buffer to store data awaiting transfer to the computer or processing by the device.

buffer2: vb. To use a region of memory to hold data that is waiting to be transferred, especially to or from input/output (I/O) devices such as disk drives and serial ports.

buffer pool: n. A group of memory or storage-device locations that are allocated for temporary storage, especially during transfer operations.

bug: n. 1. An error in coding or logic that causes a program to malfunction or to produce incorrect results. Minor bugs, such as a cursor that does not behave as expected, can be inconvenient or frustrating, but do not damage information. More severe bugs can require the user to restart the program or the computer, losing whatever previous work had not been saved. Worse yet are bugs that damage saved data without alerting the user. All such errors must be found and corrected by the process known as debugging. Because of the potential risk to important data, commercial application programs are tested and debugged as completely as possible before release. After the program becomes available, further minor bugs are corrected in the next update. A more severe bug can sometimes be fixed with a piece of software called a patch, which circumvents the problem or in some other way alleviates its effects. See also beta test, bomb2, crash2 (definition 1), debug, debugger, hang, inherent error, logic error, semantic error, syntax error. 2. A recurring physical problem that prevents a system or set of components from working together properly. While the origin of this definition is in some dispute, computer folklore attributes the first use of bug in this sense to a problem in the Harvard Mark I or the Army/University of Pennsylvania ENIAC that was traced to a moth caught between the contacts of a relay in the machine (although a moth is not entomologically a true bug).

built-in groups: n. The default groups provided with Microsoft Windows NT and Windows NT Advanced Server. A group defines a collection of rights and permissions for the user accounts that are its members. Built-in groups are therefore a convenient means of providing access to commonly used resources. See also group1.

bullet: n. A typographical symbol, such as a filled or empty circle, diamond, box, or asterisk, used to set off a small block of text or each item in a list. Round and square bullets are used to set of different levels of information. See also dingbat.

bulletproof: adj. Capable of overcoming hardware problems that, in another system, could lead to interruption of the task in progress.

bundle: vb. To combine products for sale as a lot. Frequently, operating system software and some widely used applications are bundled with a computer system for sale.

bundled software: n. 1. Programs sold with a computer as part of a combined hardware/software package. 2. Smaller programs sold with larger programs to increase the latter's functionality or attractiveness.

burn: vb. To write data electronically into a programmable read-only memory (PROM) chip by using a special programming device known variously as a PROM programmer, PROM blower, or PROM blaster. The term is also used in reference to creating read-only memory compact discs (CD-ROMs). Also called blast, blow. See also PROM.

burst1: n. Transfer of a block of data all at one time without a break. Certain microprocessors and certain buses have features that support various types of burst transfers. See also burst speed (definition 1).

burst2: vb. To break fanfold continuous-feed paper apart at its perforations, resulting in a stack of separate sheets.

burst mode: n. A method of data transfer in which information is collected and sent as a unit in one high-speed transmission. In burst mode, an input/output device takes control of a multiplexer channel for the time required to send its data. In effect, the multiplexer, which normally merges input from several sources into a single high-speed data stream, becomes a channel dedicated to the needs of one device until the entire transmission has been sent. Burst mode is used both in communications and between devices in a computer system. See also burst1.

bus: n. A set of hardware lines (conductors) used for data transfer among the components of a computer system. A bus is essentially a shared highway that connects different parts of the system--including the microprocessor, disk-drive controller, memory, and input/output ports--and enables them to transfer information. The bus consists of specialized groups of lines that carry different types of information. One group of lines carries data; another carries memory addresses (locations) where data items are to be found; yet another carries control signals. Buses are characterized by the number of bits they can transfer at a single time, equivalent to the number of wires within the bus. A computer with a 32-bit address bus and a 16-bit data bus, for example, can transfer 16 bits of data at a time from any of 232 memory locations. Most microcomputers contain one or more expansion slots into which additional boards can be plugged to connect them to the bus.

bus enumerator: n. A device driver that identifies devices located on a specific bus and assigns a unique identification code to each device. The bus enumerator is responsible for loading information about the devices onto the hardware tree. See also bus, device driver, hardware tree.

bus extender: n. 1. A device that expands the capacity of a bus. For example, IBM PC/AT computers used a bus extender to add onto the earlier PC bus and allow the use of 16-bit expansion boards in addition to 8-bit boards. See also bus. 2. A special board used by engineers to raise an add-on board above the computer's cabinet, making it easier to work on the circuit board.

business information system: n. A combination of computers, printers, communications equipment, and other devices designed to handle data. A completely automated business information system receives, processes, and stores data; transfers information as needed; and produces reports or printouts on demand. See also management information system. Acronym: BIS.

business software: n. Any computer application designed primarily for use in business, as opposed to scientific use or entertainment. In addition to the well-known areas of word processing, spreadsheets, databases, and communications, business software for microcomputers also encompasses such applications as accounting, payroll, financial planning, project management, decision and support systems, personnel record maintenance, and office management.

bus mouse: n. A mouse that attaches to the computer's bus through a special card or port rather than through a serial port. See also mouse. Compare serial mouse.

bus network: n. A topology (configuration) for a local area network in which all nodes are connected to a main communications line (bus). On a bus network, each node monitors activity on the line. Messages are detected by all nodes but are accepted only by the node(s) to which they are addressed. A malfunctioning node ceases to communicate but does not disrupt operation (as it might on a ring network, in which messages are passed from one node to the next). To avoid collisions that occur when two or more nodes try to use the line at the same time, bus networks commonly rely on collision detection or token passing to regulate traffic. See also collision detection, contention, CSMA/CD, token bus network, token passing. Compare ring network, star network.

bus system: n. The interface circuitry that controls the operations of a bus and connects it with the rest of the computer system. See also bus.

button: n. 1. A graphic element in a dialog box that, when activated, performs a specified function. The user activates a button by clicking on it with a mouse or, if the button has the focus, by hitting the Return or Enter key. 2. On a mouse, a movable piece that is pressed to activate some function. Older mouse models have only one button; newer models typically have two or more buttons.

button help: n. Help information displayed via the selection of buttons or icons. Applications such as the World Wide Web, multimedia kiosks, and computer-aided instruction often use button help icons to ease system navigation.

byte: n. Abbreviated B. Short for binary term. A unit of data, today almost always consisting of 8 bits. A byte can represent a single character, such as a letter, a digit, or a punctuation mark. Because a byte represents only a small amount of information, amounts of computer memory and storage are usually given in kilobytes (1,024 bytes), megabytes (1,048,576 bytes), or gigabytes (1,073,741,824 bytes). See also bit, gigabyte, kilobyte, megabyte. Compare octet, word.

bytes per inch: n. The number of bytes that fit into an inch of length on a disk track or a tape. Acronym: BPI.



Many definitions maybe similar to the Microsoft Computer Dictionary, 5th Edition. Purchase information found at Microsoft Press.

The contributors of these definitions is far too numerous to mention, however if you see something that you feel shouldn't be here let us know.