THE ULTIMATECOMPUTER REFERENCE
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`Over
`8,000
`Entries
`with onllne updates
`available quarterly
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`- Three new appendixes, including Y2K, file
`extensions, and Internet domains
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`- Searchabie text on CD-ROM
`
`- Extensive coverage of hardware, software, the
`Internet, and more!
`
`~ Detailed illustrations and diagrams for easy reference
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`HP-ACC-00976187
`HP-ACC-00976187
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`PUBLLSHED BY
`Microsoft Press
`A Division of Microsoft Coxporation
`.One Microsoft Way
`Redmond, Washington 98052-6399
`
`Copyright © 1999 by Microsoft Corporation
`
`All rights reserved. No part of the contents of this book may be reproduced or transmined in any form
`or by any meana without the written permission of the publisher.
`
`Library of Congress Cataloging-in-Publication Data
`Microsoft Computet Dictionary. - 4th ed.
`p. em.
`Previous eds. published under title: Microsoft Press computer
`dictioIiary
`ISBN 0-7356-0615-3
`2. Microcomputers Dictionaries.
`1. Computers Dictionaries.
`I. Microsoft Press computer dictionary.
`QA76.15.MS38
`1999
`004'.03--dc21
`
`99-20168
`CIP
`
`Printed and bound in the United States of America.
`1 2 345 6 7 8 9 ~ 432 1 0 9
`
`Distributed in Canada by ITP Nelson, d division of Thomson Canada Limited.
`
`A CIP catalogue record for this book is available from the British Library.
`
`Microsoft Press booles are available through booksollers IlJld dislIibtltors worldwide. For further information
`about international editions, contact your local Microsoft Corporation office or eontact Microsoft Press
`International directly at fax (425) 93~7329. Visit our Web site at mspress.nllcrosoft.com.
`
`Macinrosh, Power Macintosh, Quicl<l'ime, and TrueTypo fonts are registered trademarks of Apple Computer,
`Inc. Kodak i£ a registered tradellllll'k of the Eastman Kodak Company. Intel is aregistClod tradollllll'k and Indco
`is a trademark of hltel CotpOration. Active Desktop. Active Directory, ActiveMovie, Active1'latform, ActiveX,
`Authenrlcode, BackOffice, Dircctlnpul, DirectX, Microsoft, Microsoft Press, MS·DOS, MSN, NcrMeeting,
`NctShow, Visual Basic, Visual C++, Visual 1++, WebTV, WebTV Network, Win32, Wie32s, Wmdows,
`Windows NT, lind XENIX ate either registered trademarks or trademarks of Microsoft Corporation in the
`United States and/or other countries. PANTONE is a registered U1Idc.mark of PllJ1tone, Inc. Other product and
`company names mentioned herein may be the trademarks of their respective owners.
`
`The example companies. organizations, products, people, and events depicted herein are fictitious. No IISsocia(cid:173)
`lion with any real company, organization, product, person, or event is intended or should be inferred.
`
`Acquisitions Editor: Christey Bahn
`Project EeUtor: Kim Fryer
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`upon which icons, buttons, menu bars, and toolbars
`are situated. See also wallpaper. 3: The colors, tex(cid:173)
`tures, patterns, and pictures that comprise the surface
`of a Web page, upon which text, icons, graphics, but(cid:173)
`tons, and other items are situated. See also wallpaper.
`4. The condition of,an open but currently inactive
`window in a windowing environment, See also inac(cid:173)
`tive window. Compare foreground2 (definition 2).
`background Jloise 11. The noise inherent in a line or
`circuit, independent of the presence of a signal: See
`also noise.
`background printing n. The proc.ess of sending a
`document to a printer at the same' time that the com(cid:173)
`puter is performing one or more other tasks.
`background prot;cssing n. The execution of certain
`operations by the operating system or a program dur(cid:173)
`ing momentary lulls in the primary (foreground) task.
`An example of a background process is a word pro(cid:173)
`cessor program printing a document during the ti~e
`that occurs between the user's keystrokes. See also
`backgroundI ,
`background program n. A program that can run or is
`running in the back~ound. See also backgroundl .
`background task n. See backgroundl •
`back·lIt or backlit a.dj. Having a source of light, such
`as a lamp or LED, behind a (usually translucent)
`viewing surface, in order to illuminate the surface.
`back-lit display or backli.t display n. Something illu-
`minated from behind. rather than by a light source
`above or to the front.
`BackOfflce 11. A suite of software develop~d by
`Microsoft that provides certain network services.
`Designed to work with W'mdows N'l' and Wmdows
`2000, BackOffice includes such services as e-mail
`(Exchange), intranet capabilities (Site Server), net(cid:173)
`work management (Systems Management Server),
`and high-end database development (SQL Server),
`among others.
`back"panel 11. The panel at the rear of a computer
`cabinet through which most of the connections to
`outside power sources and peripherals are made. See
`the illustration.
`backplBJIe 11. A circuit board or frllIliework that sup(cid:173)
`ports other circuit boards, devices, and the intercon(cid:173)
`nections among devices, and provides power 'and
`data .signals to supported devices.
`
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`Back panel
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`Btu:kpan~1.
`
`backslash n. See \.
`Backspace key 11. 1. A key that, on IDM and compat(cid:173)
`ible 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) tha~
`erases currently selected.text or, if no text is selected.
`erases the character to the left of the insertion point
`(cursor). See the illustration.
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`b~cktrlicklng 11. The ability of an expert system to try
`alternative solutions in an attempt to find an answer.
`The various alternatives can be viewed as branches
`on a tree: in backlracking, the program follows one
`branch and, if it reaches the l:!nd without fmding what
`it seeks, backs up and tries another branch.
`back up .vb, 1. To make a duplicate copy of a pro(cid:173)
`gram, a disk, or data. See also backup. 2. To return to
`a previous stable state, such as one in which a data(cid:173)
`base is kno~ 'to be complete and consistent.
`backup n. A duplicate copy of a program, a disk, or
`data, made either for ~chiving purposes or for safe(cid:173)
`guarding valuable files from loss should the active
`copy be damaged or destroyed A backup is an "in·
`surance" copy. Some application programs automati(cid:173)
`cally make backup copies of data files, maintaining
`both the current version' ~d the preceding version on
`disk. Also called backup copy, backup file.
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`.',
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`bit
`
`bipolar ad}. 1. Having two opposite states, such as
`positi ve and negative. 2. In infonnation traosfer and
`processing, pertaining to or characleristic of 1I sig(cid:173)
`nal in which opposite voltage polarities represent 00
`and.off, true and false, or some other pair of values.
`See also nooreturo to zero. Compare unipolar. 3. In
`electronics, pertaining to or characteristic of a tran(cid:173)
`sistor having two types of charge carriers. See also
`transistor.
`BIS n, See business information system.
`BISON 11. See broadband ISDN.
`bistable adj. Of, pertaining to, or characteristic of a
`system or device that has two possible states, such as
`on and off. See also flip-flOp.
`bistable circuit n. Any circ~1 that has only two stable
`sWeS. The transition between them must be initiated
`from outside the circuit. A bistablo circuit is fapable
`of storing 1 bit of infollIUltion.
`bistable mliItivlbrator n. See flip-flop.
`BISYNC \bl'senk\ tL Short for binary synchronous
`communications protocol. A communications stan(cid:173)
`dard devalopcd by mM. BISYNC transwssions are
`encoded in either ASCII or EBCDIC. Messages can
`be of any length lend are sent in units called frames,
`optionally preceded by a mJlSsago header. BISYNC
`uses syncQronous ulIJlsmission, in which message
`elemeolS 'are sepanued by a apecific time intcuval, 50
`elIclJ frame is preceded Bnd followed by special char(cid:173)
`acters that enable the sending and receiving Il1JlCbioes
`to sYI!chronize their clocks. STX and ETX are con~
`Irol charaoters that mark the beginning and end of tho
`message text; BCe is a set of characters used to
`verify the accuracy of tmnsmission. See the illustra(cid:173)
`tion. Also called BSe.
`bit 11. Short for blnary digit. Thc smallest unit of in(cid:173)
`formation handied by a computer. One bit expresses
`a 1 or a 0 in a binary numeral. or a true or false logi.
`cal condition, and Is represented physically by an
`element such as a high or low voltage at one pOlpl in
`a circuit or 8 small spot on a disk magnetized One
`way or the other. A single bit conveys llUle infonoa(cid:173)
`tion a human would consider meaningfui. A gl'Oup of
`8 bits, however, makes up a byte. whioh can be used
`to represent many types of information, such as a
`Ic:tter of the alphabet, a decimal di$ll. or other char·
`acter. See also ASCn, binaryL, byte.
`
`binomial distribulioD 11. In statistica, a list or a func(cid:173)
`tion that describes the probabilities of tbe possible
`values of a randOm variable chaseD by nlC8ll8 of a
`Bernoulli sampling process. A Bernoulli process has
`three characteristics: each LriallUlS oniy two possible
`outcomes-success or failun:; each trial is indepen(cid:173)
`dent of ail other trials; and the probability of suc'cess
`for each trial Is coustant. A binomial distribution can
`be used to calculate the probability of getting a speci(cid:173)
`fied number of succes'ses in a Bernoulli process. For
`example, the binomial distribution can be used to
`calculate the probability of getting II 7 three times in
`20 rolls of a pair of dice. Also called Bemoulli'distri(cid:173)
`bulion.
`biometrics tL Trnditionally, the science of measuring
`and analyzing buman biological characteristics, In
`computet technology, blometric:s relates to authenti(cid:173)
`cation and security techniques that rely on mellsur·
`able, indivi,dual biological stamps to recognize or
`verify an individual's identity. For e)(ample, [luger(cid:173)
`prints, handprints, or voice-recognition might be
`used to cmable.aot:css to a computer. to a room. or to
`an electronic commerce account. Security schemes
`are generaily categorized into three levels: level 1
`relies On something the person ellIries, such as an ID
`badge with a photo or a coDlpu~er cardkey; level 2
`relies on something the person knows, such as a
`password 01' a code number; level 3, the bighest level,
`relles on something thaI is n part of tile person's bio(cid:173)
`logical makeup or behavior, such as a fmgerprinl, the
`paucm of blood vessels in n retina, or a signature.
`See also fingerprint reader, batldwriting recognition
`(definition l), voice recognition.
`bionics \bl-an'w'\ n. The study of living organisms,
`th~ cbaracteristics, and the ways they function, with
`a view loward c;reating hardware that can simulate or
`duplicate the activities of H biological system. See
`also cybernetics.
`BIOS \bnls\ ~ Acronym for basic lnpulfoutpDI 8"jS'
`tern. On PC-compatible computers, the sci. of essential
`software routines tlllit tests hardware lll: s1artUp starts
`the operating system, and supports the transfer of data
`au'long bardwlll'e devices. The BIOS is stared in read(cid:173)
`only memory (ROM) so that it can be executed when
`the computer is turned on. Although critical to perter(cid:173)
`m=, the BIOS is usually invisible to computer
`users. See also AMI BIOS, CMOS setup, Phoenix
`BIOS, ROM BIOS. Compare Toolbox.
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`board
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`bJocldng factor n. 1, The size of the chllDks in which
`data is transferred to or from a block device such as a
`disk. If fewer bytes are requested, the disk !hive will
`still read the whole block. Common blocking factors
`on personal computers are 128, 256, and 512 bytes.
`Z. The number of file records in one disk block. If the
`record length for a file is 170 bytes, a block on the
`disk contains 512 bytes, and reCords do not span
`blocks, then the blocking factor is 3, and each block
`contains 510 (170 x 3) bytes of data and 2 unused
`bytes.
`block length n. The length, usually in bytes, of a
`block of data. Block length typically ranges from 512
`bytes through 4,096 kilobytes (KB), depending on
`the purpose for which the 'block is used.
`block move n. Movement of a number of items of
`data together to a different location, as in reorganiz(cid:173)
`ing docuJUents with a word processor or moving the
`contents {)f cell ranges in a spreadsheet. Most CPUs
`have instructions that easily support block m~ves.
`block sbe n. The declared size ~f a block of data
`transferred internally within a computer, via FI'P, or
`by modem. The size is -usually chosen to make the
`most efficient use of all the hardware devices in(cid:173)
`volved. See tzlso FI'PI (definition 1).
`block structure n. The organization of a program into
`groups of statements calle;d blocks, 'which are treated
`as units. Programming languages such as Ada, C, and
`Pascal were designed around block structure. A block
`is a section of code surrounded by certain deliIniters
`(such as BEGIN and END or { and }), which signify
`thllt the intervening code can be treated as a related
`group of statements. For example. in C, each func(cid:173)
`tion is a separate block, Block structure also limits
`the scope of constants, data types, and variables de(cid:173)
`clared in a block to that block. See also function
`(definition 2), procedure, scope (definition 1).
`
`Block diagram.
`
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`'
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`, block transfer n. The mQvement of data in discrete
`blocks (groups of bytes).
`blow vb. See burn (definition 1).
`blow up vb. To terminate abnormally, as when a pro(cid:173)
`gram crosses some computational or storage bound(cid:173)
`ary lind cannot handle the situation on the other side
`as in, "I tried to draw OUt.!lide the window, and the
`graphics routines blew up." See also abend, abort.
`blue screen II. A technique used in f1l,m matte special
`effects, in which one image is superimposed on an(cid:173)
`other image. Action or objects are filmed against a
`blue screen. The desired background)s ftlmed sepa(cid:173)
`rately, lind the shot containing ,the action or objects is
`superimposed onto the background. The result is one
`image where the blue screen disappears.
`.bmp n. The file extension that identifies raster graph(cid:173)
`ics stored in bit map me format. See a!So bit map.
`BNC n. Acronym for bayonet·Neill-Conce!man.
`Named for Paul Neill of Bell Labs and Carl
`Concelman (affiliation unknown), who developed
`two earlier types 'of coaxial connectors known as the
`N connector and C connector, BNC is a type of con(cid:173)
`nector used to join sl;gments of coaxial cable. When
`one connector is'inserted into another and rotated 90
`degrees, they lock. BNC connectors are often used
`with closed-circuit television. The letters BNC are
`sometimes also considered an acrony~ for British
`Naval Connector, See the llJustration. Also called
`BNC connector. See also coaxial cable.
`
`BNC connee/or, Mar. (/eft) IUId fsmale (rIght) BNC
`COflnectar.
`BNC connector n. See BNC.
`board II. An electronic module consisting of chips and
`other elecn:onic components mounted on a flat, rigid
`substrate on which conductive paths are laid between
`the components. A personal'coll)puter 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 thl'l functionality of tile main sys(cid:173)
`tem, allowing connection to monitors, disk drives, or
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`a network. See also adapter, card (definition 1),
`motherboard.
`board computer n. See single-board.
`board level n. A level of focus In troubleshooting and
`repair that involves tracking down a problem in a
`computer to a circuit board and replacing the board.,
`This is in contrast to the component level, which in(cid:173)
`volves repairing the board itself. In many cases
`board-level repairs are made in order to quickly re(cid:173)
`store the device to working condition; the boards
`replaced are then repaired and tested for use in later
`board-level repairs. See also circuit board.
`body n. 1. In e-mail and Internet newsgroups, the con(cid:173)
`tent 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). 2. In IITML, SGML, and
`XML, a section of a document that contains the con(cid:173)
`tent of the document, along with tags describing
`characteristics of the content-for example, format
`3. A segment of a data packet containing the actual
`data.
`.
`body face rio A typeface suitable for the main te;ll:t in a
`document rather than for headings and titles. 'Because
`of their readability, fonts having serifs, such as Tunes
`and Palatino, are good body faces, although sans
`serif faces can also be used as body te;ll:t. ~ee also
`sans serif, serif. Compare display face.
`BOF \bof\ rio Acronym for birds of a feather. Meetings
`of special interest groups at trade shows, confer(cid:173)
`ences, and conventions. BOP sessions proVide an
`opportunity for people working on the same technol(cid:173)
`ogy at different companies or research institutions to
`meet and exchange their e;ll:pcriences. See beginning(cid:173)
`of-file.
`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 dif(cid:173)
`ferent documents. The size of boilerplate te;ll:t 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 tho text to which
`it is applied appear darker and heavier than the 8ur,
`rounding text. Some applications allow the user to
`
`apply a "B~ld" command to selected text; other pro(cid:173)
`grams require that special codes be embedded in the
`text before and after words that are to be printed in
`boldface. Tbi8 sentence appears In' ~oldrace.
`bombl n. A program planted surreptitiOUSly, with in(cid:173)
`tent to damage or destroy a system in some way(cid:173)
`for C;Il:ample, to erase a hard disk or cause it to be
`unreadable to the operating system. See also Trojan
`horse, virus, worm.
`bomb3 vb. To fail abruptly and completely, without
`giving ihe user a chance to recover from the problem
`short of restarting the program or system. See also
`abend, bug (definition 1), crash2 (defmition I), hang.
`bonding ~. 1. Acronym for Bandwidth ()n Demand
`Interoperability Group. 2. The process of combining
`two or more ISDN B (bearer) channels to form a
`single channel with a bandwidth greater than the
`standard B channel bandwidth of 64 Kbps, Bonding
`two B channels, for example, provides a bandwidth
`of 128 Kbps,·which is four times faster than a 28.8
`Kbps modem. Such high-speed channels are ideal for
`'video conferencing, imaging, and transfening large(cid:173)
`scale data. S~e also B cbal)Ilel, BRI, ISDN.
`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. In NetScape Navigator, a link to
`a Web page'or other URL that a user has stored in a
`local file in order to return to it later. See also Favor(cid:173)
`ites folder, hotlist, URL.
`bookmark me n. 1. A Netscape Navigator file con(cid:173)
`taining the addresses of preferred Web sites. It is syn(cid:173)
`onymous with the Favorites folder in Internet
`Expiorer and the hotlist in Mosaic. See auo Favori~s
`folder, hotlist, Internet Explorer, Mosaic. 2, A render(cid:173)
`ing of such a file in HTML fonnat, generally posted
`on a Web page for the benefit of other people. See
`alsoHTML.
`Boolean \biXl'le-;m'\ adj. Of, pertaining to, or charac(cid:173)
`teristic of logical (trile, false) values. Many lan(cid:173)
`guages directly support a Boolean data type, with
`predefined values for true and false; others use inte(cid:173)
`ger 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 algebra \blll)'le-an al'ja-bra\ n, An algebra,
`fundamental to computer operations but developed in
`the mid-nineteenth century by English mathematician
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`e-text
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`..,
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`.:..
`
`e·text \E'tekst\ n. Short for electronic tell:t. A book or
`other text-based work that is available on line in an
`electronic media format. An e-text can be read on
`line or downloaded to a user's computer for offline
`reading. See also ezine.
`Etbernet \e'th;lr-net'\ n. 1. The IEEE 802.3 st!Uldard
`for contention networks. Ethernet uses a bus or star
`topology and relies on the form of access known as
`Carrier Sense Multiple Access with Collisit;m Detec(cid:173)
`tion (CSMAlCD) to regulate communication line
`traffic. Network nodes are linked by coaxial cable, by
`fiber-optic cable, or by twisted-pair wiring, Data is
`transmitted in variable-length frames containing de(cid:173)
`livery and control information and up to 1,500 bytes
`of data. The Ethernet standard provides for baseband
`transmission at 10 megabits (10 million, bits) per sec(cid:173)
`ond and is available in various forms, 'including those
`known as Thin Ethernet., Thick Ethernet., 1OBase2,
`10Base5, 10Base-F, and 10Base-T. The IEEE stan(cid:173)
`dard dubbed 802.3z, or Gigabit Ethernet., operates at
`10 times 100 Mbps speed, See also baseband, bus
`network, coaxial cable, contention, CSMAlCD, Gi(cid:173)
`gabit Ethernet, IEEE 802 standards, twisted-pair
`cable. 2. A widely used local area network system
`developed by Xerox in 1976, from which the IEEB
`802.3 standard was developed.
`Ethemet/802.3 n. The IEEE standard for 10- or 100(cid:173)
`Mbps Iransmissions over an Ethernet network.
`Ethernet/802.3 defines both hardware and data
`packet conslrUction specifications. See also Ethernet.
`E-time l,e'tIm\ n. See execution time.
`eUquette n..See netiquette.
`ETX n. See end-of-text.
`Eudora \yClO'dllr':I\ n. An e~mail client program origi(cid:173)
`nally developed as freeware for Macintosh computers
`by Steve Dorner at the UniVersity of minois, now
`maintained in both freeware and commercial versions
`for bOth Macintosh and Wmdows by Qualconun, Inc.
`EULA \yool:1\ n. See End~User License Agreement.
`European Computer Manufacturers Association n.
`See ECMA.
`European Laboratory for Particle Physics n. See
`CERN.
`evaluation n. The determination, by a program, of the
`value of an expression or the action that a program
`statement specifies. Ev~uation can take place at
`compile time or at run time.
`
`even parity ,n. See parity.
`event n. An action lir occurrence, often generated by
`the user, to which a program might respond-for
`example, key presses, button clicks, or mouse mllve(cid:173)
`ments. See also event-driven programming.
`event-driven adj. Of, pertaining to. or being software
`that accomplishes its purpose by responding to ex(cid:173)
`ternally caused events, such as the user pressing s.
`key or clicking a button on a mouse. For example,
`an event-driven data entry form will allow the user
`to click on and edit any field at any time rather than
`forcing the user to step through a fixed sequence of
`prompts.
`event-driven processing 11. A program feature belong(cid:173)
`ing to more advanced operating-system architectures
`such as the Apple Macintosh operating system, WUl(cid:173)
`dows, and UNIX. In times past, programs were re(cid:173)
`quired to interrogate, and effectively anticipate, eVerJ
`device that was expected to interact with the program.
`such as the keyboard, mouse, printer, disk drive, and
`serial port. Often, unless sophisticated programming
`techniques were used, one of two events happening at
`the same instant would be lost. Event processing
`solves this problem through the creation and mainte(cid:173)
`nance of an event queue, Most common events that
`occur are appended to the event queue for the program
`to process in tum; however, certain types of events can
`preempt others if they have a higher priority. Art event
`can be of several types, depending on the specific op(cid:173)
`erating system considered: pressing a mouse button or
`keyboard key, inserting a disk, clicking on a window,
`or receiving information from a device driver (as for
`managing the transfer of data from the serial port or
`from a network connection). See also autopolling.
`event, interrupt.
`event·driven programming n. A type of program(cid:173)
`ming in which the program constantly evaluates aDd
`responds to sets of events, such as key presses or .
`mouse movements. Event-driven programs are tyPi(cid:173)
`cal of Apple Macintosh computers, although most
`, graphical interfaces, such as Wmdows or t!le X,
`Window System, also use such an approach. See
`also event.
`eu- prefix A prefix meaning one quintillion (lOJI). In
`computing, which is based On the binary (base-2)
`,
`numbering system, exs.- has a literal value of
`1,152,921,504,606,846,976, which is the power of 2
`(2"') closest to one qUintillion. Abbreviation: E.
`
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`Interactive voioe responl>e.,
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`-
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`~ t
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`•
`I
`•
`, •• '_._'"'_~"'"
`
`•
`
`interactive voice response n. A computer that oper(cid:173)
`ates through the telephone system, in which input
`commands and d'ata are transmitted to the computer
`as spoken words and numbers,'or tones and dial
`pulses generated by a telephone instrument; and out(cid:173)
`put instructions and data are received from the com(cid:173)
`puter as prerecord~ or synthesized speech. For
`example, a dial-in service that provides airline flight
`schedules when you press certain key codes on your
`telephone is an interactive voice response system. ,
`Also called IVR.
`Interactive voice system n. See interactive voice
`response.
`interapplicatlon conununlcatfon n. The process of
`one program sending messages to another program.
`For example, some e-mail programs allow users to
`click on a URI.. within the message. After the user
`clicks on the URL, browser saftware will automati(cid:173)
`cally launch and access the URL.
`interblock gap n. See inter-record gap.
`Interchange File Format n. See .iff.
`Interchange Format n. See Rich Text Format.
`interconnect n. See System Area Network.
`interface n. 1. The point at which a connection is made
`between two elements so that they can work with each
`other or exchange information. i. Software that en(cid:173)
`ables a program to work with the user (the user inter(cid:173)
`face, which can be a command-line interface,
`menu-driven, or a graphical user interface), with an(cid:173)
`other program such as the operating system, or with
`the computer's hardware. See also application pro(cid:173)
`gramming interface, graphical user interface. 3: A
`card, pl~, or other device that connects pieces of
`hardware with the computer so that information can be
`moved from place to place. For example, standardized
`interlaces such as RS-232-C standard and SCSI enable
`communications between computers and printers or
`disks. See also RS-232-C standard, SCSI.
`interface adapter n. See netWork adapter.
`interface card n, See adapter.
`interference n. 1. Noise or other extemal sigDals that
`affect the performance of a communications channel.
`2. Electromagnetic signals that can disturb radio or
`television reception. The signals can be generated
`naturn).ly, as in lightning, or by electronic devices,
`such as computers.
`Interior Gateway Protocol n. See lOP.
`
`Interior Gateway Routing Protocol n. See IGRP.
`interlace scanning n. A display technique designed to
`reduce flicker and distortions in television transmis(cid:173)
`sions; also used with some PC monitors. In interlace
`scanning the electron beam in the television or moni(cid:173)
`tor refr~hes alternate sets of scan lines in successive
`top-to-bottom sweeps, refreshing all even lines on one
`pass, and all odd lines on the other. Interlaced images
`are not as clear as those produced by the progressive
`scanning typical of newer computer Jl).onitors. Inter(cid:173)
`lace scanning is, however, the standard method of dis(cid:173)
`playing analog broadcast television images. Also
`called interlacing. Compare progressive scanning.
`Interlaclng n, A technique used in some raster-scan
`video displays in which the eleCtron beam refreshes
`(updates) all odd-numbered scan liries in one vertical
`sweep of the screen and all even-numbered scan lines
`in the next sweep. Because o'f the screen phosphor's
`ability to maintain an image for a short time before
`fading and the tendency of the human eye to average
`or blend subtle differences in light intell)lity, the hu(cid:173)
`man viewer sees a complete display, but the amoWit
`of information camed by the display signal and the
`Dumber cif lines that must be displayed per sweep are
`halved. Compare noninterlaced.
`Interleave vb. To arrange the sectors on a hard disk in
`such a way that Mter one sector is read, the next sec(cid:173)
`tor in numeric sequence will arrive at the head when
`the computer is ready to accept it rather than before,
`which would make the computer wait a whole revo(cid:173)
`lution of the platter for the sector to come back. In(cid:173)
`~rleaving is set by the format utility that initializes a
`disk for use with a given computer.
`interleaved memory n. A method of organizing the
`addresses In RAM memory in order to reduce wait
`states, In interleaved memory, adjacent locations are
`stored in different rows of chips so that after access(cid:173)
`ing a byte, the process~r does not have to wait an
`. entire memory cycle before accessing the next byte.
`See also access time (definition 1), wait state.
`interlock vb. Th prevent a device from acting while
`the current operation is in .progress.
`intermediate language n. A computer language used
`as an intermediate step between the original source
`language, usually a high-level language, and the'tar(cid:173)
`get language, usually machine code. Some high-level
`compilers use assembly language as an intermediate
`language. See also cO,mpliet (definition 2), object code.
`
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`phase-locked
`
`phon4?ime
`
`cally changfug the phase of the carrier, in order to
`increase the bit density of the transmission. See also
`Manchester coding, phase. 2. A recordinft technique
`used with magnetic storage devices in which each
`data-holding unit is divided into two paIts, each of
`which is IIlllgnetized so that it is opposite in pOlarity
`to the other.
`phase-locked adj. Of, pertaining to, or characteristic
`of the relationship between two signals whose phases
`relative to each' other are kept constant by a control(cid:173)
`ling mechanism, such as an electronic device.
`phase modulation 11. A method of imposing informa(cid:173)
`tion onto a wavefonn signal by shifting the phase of
`the wave to represent infonnation, such as the binary
`digits 0 and 1. See the illustration. See also phase(cid:173)
`shift keying.
`phase-shin keying 11. A communications method used
`by modems to encode data that relies on phase shifts
`in a carrier wave to represent digital information, In
`its simplest farro, phase-shift keying allows ,the phase
`of the carrier wave to be in either of two states:
`shifted 0 degrees or shifted 180 degrees, effectively
`reversing the phase of the wave. This straightforward
`phase-shift keying, however, is useful only when
`each phase can be measured against aD unchanging
`reference value, so a more sophisticated technique
`called differential phase-shift keying, or DPSK, is '
`used in IDJUly modems. In differential phase-shift
`
`keying, the phase of the camer wave is shifted to
`represent more than two possible states, and each
`state is interpreted as a relative change from the
`state preceding it. No reference values or timing
`considerations are required, and because more than
`two states are possible, more than one binary digit
`can represent each state. Acronym: PSK. See also
`phase modulation:
`Phoenix BIOS \fe'niks bi'os\ 11. An mM-compalible
`ROM BIOS IDJUlufactured by Phoenix Technologies,
`Ud. A popular ROM BIOS in many PC "clone" com·
`puters, the Phoenix BIOS was an early leader among
`the ffiM·compatible computers shortly after they
`began to appear in the marketplace. See also BIOS,
`ROM BIOS. Compare AMI BIOS.
`phone connector n. An attachment, usually an RJ·ll
`connector, used to join a telephone J..i.ile to a device
`such as a modem. Sec the illustration.
`
`~""-
`-t., ',
`
`Phon' tOnnector.
`phoneme \fo "nem\ 11. In lIDguistics, the smallest unit
`of speech that distinguishes one word sound from
`another. Phonemes are the elements on which com(cid:173)
`puter speech is based.
`
`Phase
`180· phase shift
`1..--------.....1......--------,1 ..1--..1'--....
`90·
`
`Baseline
`
`270·
`
`P""se modutatJon. A phase shift 0/180 degrees.
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