A Dictionary of
`Coillputing
`
`Many entries in this dictionary have recommended web
`links. When you see the above symbol at the end of an entry
`go to the dictionary's web page at http://www.oup.com/uk/
`reference/resources/ computing, click on Web links in the
`Resources section and locate the entry in the alphabetical
`list, then click straight through to the relevant websites.
`
`

`
`A Dictionary of
`
`Computing
`
`SIXTH EDITION
`
`OXFORD
`
`UNIVERSITY PRESS
`
`

`
`f-Nq1..
`0 l0811(o
`
`_
`
`OXFORD
`
`UNIVERSITY PRESS
`Great Clarendon Street, Oxford OX2 6DP
`Oxford University Press is a department of the University of Oxford.
`It furthers the University's objective of excellence in research, scholarship,
`and education by publishing worldwide in
`Oxford NewYork
`Auckland Cape Town Dar es Salaam Hong Kong Karachi
`Kuala Lumpur Madrid Melbourne Mexico City Nairobi
`New Delhi Shanghai Taipei Toronto
`With offices in
`Argentina Austria Brazil Chile Czech Republic France Greece
`Guatemala Hungary Italy Japan Poland Portugal Singapore
`South Korea Switzerland Thailand Turkey Ukraine Vietnam
`Oxford is a registered trade mark of Oxford University Press
`in the UK and in certain other countries
`Published in the United States
`by Oxford University Press Inc., New York
`
`©Market House Books Ltd, 1983, 1986, 1990, 2004, 2008
`
`The moral rights of the author have been asserted
`Database right Oxford University Press (maker)
`
`First edition 1983
`Second edition 1986
`Third edition 1990
`Fourth edition 1996
`Fifth edition 2004
`Sixth edition 2008
`
`AU rights reserved. No part of this publication may be reproduced,
`stored in a retrieval system, or transmitted in any form or by any means,
`without the prior permission in writing of Oxford University Press,
`or as expressly permitted by law, or under terms agreed with the appropriate
`reprographics rights organization. Enquiries concerning reproduction
`outside the scope of the above should be sent to the Rights Department,
`Oxford University Press, at the address above
`
`You must not circulate this book in any other binding or cover
`and you must impose this same condition on any acquirer
`
`British Library Cataloguing in Publication Data
`Data available
`
`Library of Congress Cataloging in Publication Data
`Data available
`
`Typeset by Market House Books Ltd.
`Printed in Great Britain
`on acid-free paper by
`Clays Ltd, St Ives plc
`ISBN 978-0-19-923401-1
`
`10 9 8 7 6 5 4 3 2 1
`
`~
`.......... --------------------~~~-
`
`.I
`,1
`
`l
`-l
`
`

`
`engineering of computer-based systems
`
`encapsulation 1. See OBJECT, INFORMA(cid:173)
`".r:ION HIDING. 2. See INTERNETWORKING.
`encoder 1. The means by which an encod(cid:173)
`\ing process is effected (seeconE). It may be
`implemented in hardware or software, the
`cprocess being algorithmic in nature. 2. A
`··logic circuit, usually an integrated circuit,
`that generates a unique n-bit binary word,
`indicating which of its 2 n input lines is ac(cid:173)
`tive, i.e. at logic 1. A keyboard encoder, for
`example, may be required to generate a
`unique binary code indicating which key on
`the keyboard has been pressed.
`If two or more of the device inputs can be
`active simultaneously then a priority en(cid:173)
`coder is required, which usually encodes
`only the highest-order data input.
`encoding 1. The transformation of a mes(cid:173)
`sage into an encoded form. See CODE. 2. The
`representation of symbols in some alphabet
`by symbols or strings of symbols in some
`other alphabet. A common example is *bi(cid:173)
`nary encoding.
`encryption The processing of a message
`by a sender in order to render it unintelligi(cid:173)
`ble to other than authorized recipients. See
`also CRYPTOGRAPHY.
`end-around-carry A type of carry that is
`required when a *radix-minus-one comple(cid:173)
`ment representation of integers is used and
`two integers so represented are summed. If a
`carry is generated at the most significant end
`of the two numbers, then this carry must be
`added to the digit at the least significant end
`of the result to give the radix-minus-one
`complement representation of the sum.
`end-around shift Another name for cir(cid:173)
`cular shift See SHIFT.
`endomorphism A *homomorphism from
`an *algebra to itself.
`endorder traversal Another name for
`postorder traversal.
`end-to-end control Control acting be(cid:173)
`tween two applications that are communi(cid:173)
`cating across one or more networks. Data
`traversing a network must be protected
`against a number of possible forms of error.
`An individual unit of data may be corrupted,
`lost completely, or delivered more than
`once; successive units of data may be deliv(cid:173)
`ered in the wrong order. The sender may at(cid:173)
`tempt to transmit data more quickly than
`
`the receiver can receive it, or some part of
`the route can actually carry it. Within the
`network, the transmitter and receiver at the
`two ends of an individual link will cooperate
`to control some of these errors, and this is
`known as point-to-point control. However,
`it may also be necessary to require the appli(cid:173)
`cations at each end of the overall connection
`to cooperate in protecting against other
`forms of error, and this is end-to-end con(cid:173)
`trol.
`end-to-end encryption The transfer of
`an encrypted message across a system with(cid:173)
`out intermediate stages of decryption and
`reencryption. Compare LINK ENCRYPTION.
`energizer A hardware or software mecha(cid:173)
`nism that is used as an aid in testing the be(cid:173)
`havior of a subsystem. The intention is that
`the energizer should drive the subsystem in
`a way that simulates its actual application,
`and should at the same time analyze the re(cid:173)
`sponses from the subsystem in order to de(cid:173)
`tect any erroneous behavior.
`engine 1. A component of a software sys(cid:173)
`tem that handles a specific aspect of pro(cid:173)
`cessing. Engines thus form part, or possibly
`the whole, of an application's *back end. For
`example, a database engine provides data(cid:173)
`base services other parts of the system; a
`search engine provides searching services;
`and so on. Engines can be shared among
`several applications - for example, through
`the *client/ server model-and are often
`bought from a third-party specialist supplier.
`2. Another name for back end.
`engineering of computer-based sys(cid:173)
`tems (ECBS) A narrower form of *systems
`engineering that addresses only those sys(cid:173)
`tems which are computer-based. This is a
`very important subset of systems engineer(cid:173)
`ing, but is still very much wider than *soft(cid:173)
`ware engineering. It encourages a holistic
`view of a system, its environment, and its
`components. Often the components of com(cid:173)
`puter-based systems are also (lower-level)
`computer-based systems. ECBS pays great
`attention to addressing nonfunctional prop(cid:173)
`erties of a proposed design, and the need for
`give-and-take between different design op(cid:173)
`tions prior to committing to an implementa(cid:173)
`tion. Give-and-take is seen as a crucial
`aspect of such developments because it is
`here that competing requirements and
`
`

`
`informatics
`
`250
`
`informatics The use of computers to
`maintain and analyze large amounts of data.
`The term is applied particularly with respect
`to databases of chemical compounds or re(cid:173)
`actions (chemoinformatics) or databases in
`biochemistry or cell biology (bioinformat(cid:173)
`ics).
`information Generally, information is
`whatever is capable of causing a human
`mind to change its opinion about the current
`state of the real world. Formally, and espe(cid:173)
`cially in science and engineering, informa(cid:173)
`tion is whatever contributes to a reduction in
`the uncertainty of the state of a system; in
`this case, uncertainty is usually expressed in
`an objectively measurable form. Commonly,
`this is done by means of Shannon's *en(cid:173)
`tropy. Nevertheless, this formula for uncer(cid:173)
`tainty involves probabilities, and these may
`well have to be subjective. If that is so, the
`formal measurement must be qualified as
`dependlng on subjective probabilities, and
`"uncertainty" must be replaced by "opinion,
`or personal estimate, of uncertainty".
`Information must be distinguished from
`any medium that is capable of carrying it. A
`physical medium (such as a magnetic disk}
`may carry a logical medium (data, such as
`binary or text symbols). The information
`content of any physical objects, or logical
`data, cannot be measured or discussed until
`it is known what range of possibilities existed
`before and after they were received. The in(cid:173)
`formation lies in the reduction in uncer(cid:173)
`tainty resulting from the receipt of the
`objects or the data, and not in the size or
`complexity of the objects or data themselves.
`Questions of the form, function, and seman(cid:173)
`tic import of data are only relevant to infor(cid:173)
`mation inasmuch as they contribute to the
`reduction of uncertainty. If an identical
`memorandum is received twice, it does not
`convey twice the information that its first oc(cid:173)
`currence conveyed: the second occurrence
`conveys no information at all, unless, by
`prior agreement, the number of occurrences
`is itself to be regarded as significant.
`Information has ramifications in security,
`politics, culture, and the economy, as well as
`in science and engineering. The extent to
`which information is used as an economic
`commodity is one of the defining character(cid:173)
`istics of the "post-industrial" society, hence
`the phrase "the information society".
`
`information destination See SHANNON' s
`MODEL
`information engineering The engineer(cid:173)
`ing approach applied to *information sys(cid:173)
`tems. The term shows considerable variation
`in scope. At its broadest, it refers to the engi(cid:173)
`neering discipline covering a spectrum from
`*software engineering and *systems engi(cid:173)
`neering to device-level electronics. At its
`most limited (but perhaps best known}, it is
`the name of a specific proprietary method
`for the development of organizational infor(cid:173)
`mation systems, primarily associated with
`James Martin; this method begins with *en(cid:173)
`terprise modeling and carries through to the
`generation of program code, and a number
`of software toolsets are available for its sup(cid:173)
`port.
`information hiding A principle, used
`when developing an overall *program struc(cid:173)
`ture, that each component of a program
`should encapsulate or hide a single design
`decision. The principle was first expounded
`by David Pamas, who advocated an ap(cid:173)
`proach to program development in which a
`list is prepared of design decisions that are
`particularly difficult or likely to change;
`vidual components, known as modules, are
`then defined so that each encapsulates one
`such decision. The interface to each module
`is defined in such a way as to reveal as little
`as possible about its inner workings.
`This approach leads to modules that are
`readily understood and can be developed in"'.
`dependently. More important, it also leads
`to programs that are easy to change, with
`manv desired changes requiring modifica(cid:173)
`tion of only the inner workings of a single
`module.
`information management system
`term sometimes used synonymously with
`*database management system (DBMS} al~
`though normally used in a more general
`·
`sense. The term has no widely accepted
`definition and thus can be applied to any
`system of software that facilitates the
`age, organization, and retrieval of·
`tion within a computer system, wi
`implication that it need have all the
`characteristics of a DBMS. The info
`held mav include sound fragments,
`and video sequences in addition to
`textual and numerical information.
`newer forms of computer-held inti
`are sometimes argued as be.ing a defi
`
`

`
`Internet Architecture Board
`
`262
`
`Internet Architecture Board (IAB) See
`INTERNET SOCIETY.
`Internet cafe SeeCYBERCAFE.
`Internet Engineering Steering Group
`(IESG) See INTERNET SOCIETY.
`Internet Engineering Task Force (IETF}
`See INTERNET SOCIETY.
`Internet Explorer Microsoft's web
`brows-ing software, first introduced in 1995.
`See BROWSER.
`Internet Message Access Protocol See
`IMAP.
`internet protocol A *protocol that allows
`traffic to pass between networks. The most
`widely used is *IP, the Internet Protocol. See
`also INTERNETWORKING.
`Internet Protocol Security See IPSEC.
`Internet service provider See ISP.
`Internet Society (ISOQ A professional
`membership society that promotes the use
`and future development of the Internet. It
`has individual and organization members all
`over the world and is governed by an elected
`board of trustees. ISOC coordinates various
`groups responsible for Internet infrastruc(cid:173)
`ture. These include the Internet Engineering
`Task Force (IETF), the Internet Architecture
`Board (!AB}, and the Internet Engineering
`Steering Group {IESG). The IETF develops
`technical standards for the Internet. The lAB
`has overall responsibility for the architecture
`and adjudicates on disputes about stan(cid:173)
`dards. The IESG, along with the !AB, reviews
`standards proposed by the IETF. See also
`IANA.
`1@l11a111~•1vu+*
`• The Internet Society home page
`internetworking Connecting several
`computer •networks together to form a sin(cid:173)
`gle higher-level network, as occurs in the
`*Internet. There are two basic approaches:
`encapsulation and translation. The junc(cid:173)
`tions between networks are called •gate(cid:173)
`ways, and their functions depend on which
`internetworking approach is taken.
`When encapsulation is used, a new proto(cid:173)
`col layer (or layers) is defined; this provides
`uniform semantics for services such as
`*datagram packet switching, *electronic
`mail, etc. When a message is entered into the
`internetwork, it is wrapped (encapsulated) in
`
`a network-specific protocol {local network
`datagram headers, or *virtual circuits). The
`encapsulated packet is sent over the network
`to a gateway, which removes the old net(cid:173)
`work-specific encapsulation, adds a new set
`of network headers, and sends the packet
`out on another network. Eventually the mes(cid:173)
`sage reaches its destination, where it is con(cid:173)
`sumed.
`When protocol translation is used, mes(cid:173)
`sages are sent on a local network using the
`protocols and conventions of that network. A
`gateway receives the message and trans(cid:173)
`forms it into the appropriate message on an(cid:173)
`other network; this may involve interpreting
`the message at multiple protocol levels.
`The encapsulation approach provides a
`uniform set of semantics across all networks,
`while the translation approach results in
`unanticipated problems due to subtle differ(cid:173)
`ences between protocols. The encapsulation
`approach generally requires that new soft(cid:173)
`ware be written for all hosts on all networks,
`while the translation approach requires new
`software only in the gateways. See also IP.
`interoperability The ability of systems to
`exchange and make use of information in a
`straightfmward and useful way; this is en(cid:173)
`hanced by the use of standards in communi(cid:173)
`cation and data format. For example, a -
`microcomputer conforming to the *SCSI
`standard can be connected to any SCSI pe(cid:173)
`ripheral device - i.e. many different hard
`disks, printers, etc. In software, operating
`systems that run on different CPUs, and Mi(cid:173)
`crosoft *Word's ability to read files created
`using *Excel are both examples of interoper(cid:173)
`ability.
`interpolation A simple means of approxi(cid:173)
`mating a functionj{x) in which the approxi(cid:173)
`mation, say p(x), is constructed by requiring
`that
`p(x;) =fix;), i= 0,1,2,. .. ,n
`Here fix;) are given values p(x;) that fit ex(cid:173)
`actly at the distinct points x; (compare
`SMOOTHING). The value of/can be approxi(cid:173)
`mated by p(x) for x * x;. In practice pis often
`a polynomial, linear and quadratic polyno(cid:173)
`mials providing the simplest examples. In
`addition the idea can be extended to include
`matching of p(x;) with f'(x;); this is Hermite
`interpolation. The process is also widely
`used in the construction of many numerical
`methods, for example in *numerical integra- -
`tion and *ordinary differential equations.
`
`

`
`o and is usually associated with mem(cid:173)
`compaction.
`ge collection SeeGARBAGE.
`e in garbage out (GIGO) An
`ciation of the important computing
`at all input, however absurd, will
`d according to a program's algo(cid:173)
`d appropriate output generated. If
`tis garbage, then the output will in(cid:173)
`also be garbage. This tru.th is often
`recognized, especially by non-computer
`speciali&ts, who tend to blame "the com-
`.• puter" for incorrect results when the fault
`actually lies with mistakes in the input.
`gate See LOGIC GATE.
`gate array A form of *programmable de(cid:173)
`vice in which the component *logic gates
`can be interconnected in an arbitrary man(cid:173)
`ner during manufacture to give a *combina(cid:173)
`tional or•sequential circuit of considerable
`*height.
`Gates, Bill (William Henry G.; 1955-
`US businessman and programmer. Gates
`began programming at school and in 1975,
`while an undergraduate at Harvard, wrote a
`BASIC interpreter with his friend Paul Allen
`for an early microcomputer, the MITS Altair.
`This Gates-Allen partnership was the genesis
`of *Microsoft, and Gates left Harvard to de(cid:173)
`velop the business. While he personally su(cid:173)
`pervised Microsoft's products in the early
`years, he became better known for the busi(cid:173)
`ness acumen that has built Microsoft into
`the world's largest software company, in the
`process making himself the world's richest
`person. Notable successes include securing
`the contract {1980) to supply an operating
`system for the original IBM personal com(cid:173)
`puter while retaining the right to market it
`separately (as *MS-DOS) ; and the exploita(cid:173)
`tion of the success ofWindows 3.x after 1990
`to achieve dominance of the PC market(cid:173)
`place. Gates was CEO of Microsoft until
`2000, then chief software architect until
`2006; he continues as Chairman. He has
`used part of his personal fortune for philan(cid:173)
`thropic purposes, founding the Bill &
`Melinda Gates Foundation with his wife in
`2000.
`gateway A device that interconnects two
`*networks, and whose presence is usually
`visible to network users (as distinct from a
`*bridge, whose presence is generally not vis-
`
`GCD
`
`ible). A gateway may be required to deal with
`one or more of the following differences be(cid:173)
`tween networks it connects:
`(a} change of addressing *domain -where
`the networks have addressing domains man(cid:173)
`aged by separate groups, a gateway may be
`used to handle address transformations for
`messages traversing the gateway;
`(b) control of charging-where the networks
`have different approaches to charging (e.g. a
`local area network that imposes no charges
`connecting to a wide area network that
`charges on a per-packet basis), a gateway
`may be used to handle user authorization
`and usage accounting;
`(c} change ofprotocol-wherethe networks
`use different protocols, a gateway may be
`used to carry out necessary protocol conver(cid:173)
`sion (if practicable) or to intercept attempts
`by a user on one network to use functions
`not available on the other and to supply suit(cid:173)
`able responses.
`The terms bridge, gateway, and *relay are
`among those whose meanings vary between
`different communities of users at a given
`time, and within a given community of users
`at different times.
`gather write The function of writing to
`memory a block of data comprising items of
`data that have been retrieved directly from
`scattered memory locations and/or registers.
`Gaussian distribution Another name for
`normal distribution.
`Gaussian elimination See LINEAR ALGE(cid:173)
`BRAIC EQUATIONS.
`Gaussian noise *Noise whose distribu(cid:173)
`tion of amplitude over time is *Gaussian.
`Gaussian quadrature See NUMERICAL IN(cid:173)
`TEGRATION.
`GB {orGb) Symbolsforgigabyte. SeeGIGA-,
`BYTE.
`Gbps Abbrev. for gigabits per second, i.e.
`usually 109 bits per second. SeeGIGA·, BPS.
`GBS method The Gragg-Burlisch-Stoer
`*extrapolation method based on theoretical
`results obtained by Gragg, implemented by
`Burlisch and Stoer. SeeGRAGG's EXTRAPOLA(cid:173)
`TION METHOD.
`Gbyte Abbrev.forgigabyte. SeeGIGA-, BYTE.
`GCD Abbrev. for greatest common divisor.
`
`

`
`refinement
`
`430
`
`defined outside the function, except for the
`variables passed as parameters.
`refinement The process in programming
`whereby higher-level or abstract ideas are
`progressively reexpressed in terms of Iower(cid:173)
`level or concrete ones. This can involve both
`the implementation of procedures in terms
`of lower-level procedures, and also the rep(cid:173)
`resentation of abstract data in terms of more
`concrete data. Both kinds of refinement can
`involve •specifications, with each step of
`refinement being shown to preserve the
`specified behavior of the procedure or data
`type being refined. Although both terms are
`rather fluid in meaning, there is a possible
`distinction to be made between refinement
`and *program transformation, with the latter
`involving the replacement of one program
`fragment by an equivalent one at the same
`level of abstraction rather than its represen(cid:173)
`tation in terms of a lower level of abstrac(cid:173)
`tion.
`Refinement and transformation are two of
`the main ideas in the increasingly important
`study of the systematic derivation of correct
`programs from specifications.
`reflectance function A function that
`defines the spatial distribution and the
`wavelength composition of the light
`reflected from an object's surface.
`reflectance model A mathematical
`model of how light is reflected from a surface
`based on a *reflectance function. The basic
`reflectance model assumes that all surfaces
`are perfect mirrors. More realistic models
`use reflectance functions that more accu(cid:173)
`rately represent the properties of real sur(cid:173)
`faces (see also SPECULAR REJII.ECTION,
`COOK-TORRANCE MODEL}.
`reflexive closure SeeTRANSITIVE
`CLOSURE.
`reflexive relation A *relation R defined
`on a set Sand having the property that
`xRx
`for all elements xin S
`The relation "is the same age as" defined on
`the set of people is reflexive. Compare IR(cid:173)
`REFLEXIVE RELATION.
`refresh {regenerate) 1. To replenish the
`charge on the storage capacitors used in *dy(cid:173)
`namic memory cells and other similar de(cid:173)
`vices. Some devices are provided with
`
`internal circuitry that automatically re(cid:173)
`freshes dynamic cells whenever these cells
`are read. The word refresh is also used as a
`noun. 2. To repeat at regular intervals the
`display of digital information on a •cathode(cid:173)
`ray tube or television monitor in order that
`the display can appear persistent. See also
`REFRESH FREQUENCY.
`refresh frequency The frequency with
`which a display on a cathode-ray tube is re(cid:173)
`generated. To avoid *flicker this must be
`made as high as possible. See CFF.
`refutation A method of reasoning used in
`logic to refute statements, i.e. to prove them
`false.
`regenerate Another term for refresh.
`register A group of (usually) *bistable de(cid:173)
`vices that are used to store information
`within a computer system for high-speed ac(cid:173)
`cess. A register of n bistables can store a
`word of length n bits, which can represent
`any n bits ofinformation. Different interpre(cid:173)
`tations can be given to the bit configuration
`stored in the register; for example, the
`configuration could represent an instruc(cid:173)
`tion, a binary number, an alphanumeric
`character, etc. A register is often the same
`size as the computer word; it may also be
`byte- or character-size or some other size as
`required. Some registers can behave as
`*counters as well, or they may behave as
`*shift registers. See also MEMORY HIERAilCHY.
`register insertion ring See RING NET(cid:173)
`WORK.
`register optimization SeeoPTIMIZATION.
`register transfer language (RTL) Any of
`several programming languages that allow
`the declaration of-register configurations
`within a structure to perform a computation.
`The timing of transfers between registers, to
`describe the behavior, is specified by the
`order in which such transfers are interpreted
`during the execution of the program. See also
`CHDL.
`regression analysis A statistical tech(cid:173)
`nique that is concerned with fitting relation(cid:173)
`ships between a dependent variable, y, and
`one or more independent variables, Xv x2,. •• ,
`usually by the method of *least squares.
`A linear regression model is one in which
`the theoretical mean value,µ;, ofth.e obser-
`
`

`
`DICTIONARY
`ccccMc+cc'ccCM'Cf 0 f
`COMPUTER
`TERMS
`
`EIGHTH EDITION
`
`The Best Computer Dictionary in Print
`
`C~mpletely revised and updated
`
`Contains extensive Internet coverage
`
`Mvre than 4,000 entries, terms, and acronyms
`
`

`
`Dedication
`
`For Suzanne, always
`
`Webster's New World"' Dictionary of Computer Terms,
`8th Edition
`
`Copyright © 2000 by
`IDG Books Worldwide, Inc.
`An International Data Group Company
`919 E. Hillsdale Blvd.
`Suite 400
`Foster City, CA 94404
`
`All rights reserved including the right of reproduction in whole
`or in part in any form.
`
`For general information on IDG Books Worldwide's books in
`the U.S., please call our Consumer Customer Service depart(cid:173)
`ment at 1-800-762-2974. For reseller information, including
`discounts, bulk sales, customized editions, and premium sales,
`please call our Reseller Customer Service department at
`1-800-434-3422.
`
`A Webster's New World™ Book
`
`WEBSTER'S NEW WORLD DICTIONARY is a registered
`trademark of IDG Books Worldwide, Inc.
`
`Library of Congress Catalog Number: 98-68180
`
`ISBN: 0-02-863777-1
`
`Manufactured in the United States of America
`
`34567
`
`1 02 03 04
`
`

`
`continuous-tone printer 127
`is Symantec's ACT!, which includes a calendar and
`ng. See personal information manager (PIM).
`
`t manager A program designed to help keep track of
`by maintaining a list of addresses, phone numbers, and
`bers. Information is also maintained through the use of a
`pad, automatic telephone dialing with a modem, and search
`sort capabilities.
`
`In local area networks (LANs), a channel access
`od in which access to the communication channel is based
`first-come, first-served policy. See CSA1AICD and device
`
`ensitive help
`In an application program, a user(cid:173)
`ance mode that displays documentation relevant to the
`mmand, mode, or action you are now performing. Context(cid:173)
`itive help reduces the time and keystrokes needed to get
`reen help.
`
`~ontext switching Changing from one program to another
`Without exiting either program. See multiple pro,t.?ram loading.
`
`contiguous Adjacent; placed one next to or after the other. A
`range of cells in a spreadsheet is often, but not always, made up
`of contiguous cells. Its opposite is noncontiguous.
`
`continuous paper Paper manufactured in one long strip, with
`perforations separating the pages, so that you can feed the paper
`into a printer with a tractor-feed mechanism. Synonymous with
`continuous-feed paper. Also called fat!fold paper. The opposite is
`rnt-sheet paper, in which every sheet is a separate piece.
`
`continuous speech recognition The decoding of continu(cid:173)
`ous human speech (without artificial pauses) into transcribed
`text by means of a computer program.
`
`continuous-tone image Printer output in which colors
`and shades of gray blend smoothly together, as they would in
`a chemically printed photograph.
`
`continuous-tone printer A printer that can generate photo(cid:173)
`realistic output, with smooth gradations between colors or
`shades of gray.
`
`

`
`118 Component Object Model
`Component Object Model See COM.
`
`component reusability
`In programming, the capability of
`creating a program module that can perform a specific task and
`be used in another program with little or no modification.
`
`complex instruction set computer (CISC) A type of cen(cid:173)
`tral processing unit (CPU) that can recognize as many as 100
`or more instructions, enough to carry out most computations
`directly. Most microprocessors are CISC chips. The use of
`reduced instruction set computer (RISC) technology, however,
`is becoming increasingly common in professional workstations.
`Apple's Power Macintosh computers use a compromise
`RISC/CISC processor.
`
`compose sequence A series of keystrokes that lets you enter
`a character not found on the computer's keyboard. See ASCII
`character set and extended character set.
`
`composite See comp.
`
`composite color monitor A monitor that accepts a standard
`video signal that mixes red, green, and blue signals to produce
`the color image. Display quality is inferior to that of RGB mon:..
`itors. See composite video.
`
`composite video A method for broadcasting video signals ·
`which the red, green, and blue components, as well as horizo
`and vertical synchronization signals, are mixed together. Regu(cid:173)
`lated by the U.S. National Television Standards Committee
`(NTSC), composite video is used for television. Some compu
`have composite video outputs that use a standard RCA pho
`plug and cable, such as on the backplane of a hi-fi or stereo
`tern. See composite color monitor and RGB monitor.
`
`In multimedia, a device, such as a MID
`compound device
`sequencer, that reproduces sound or other output that you
`recorded in a specific media file.
`
`In object linking and embedding
`compound document
`(OLE), a single file created by two or more applications.
`you use OLE to embed a Microsoft Excel chart into a Mi
`Word document, for example, the resulting file contains
`Word text as well as the Excel object. The object cont ·
`information Excel needs to open the chart for editing. This
`information results in file sizes considerably larger than no
`See OpenDoc.
`
`

`
`encryption 189
`ation The duplication within a device of another
`e's functional capability, or a device designed to work
`like another. In telecommunications, for example, a per(cid:173)
`computer emulates a dumb terminal (a terminal without
`n microprocessor) for online communication with a dis(cid:173)
`mputer. With printers, lesser-known brands emulate
`models such as Hewlett-Packard's LaserJet line.
`
`ation sensing See automatic emulation switching and auto(cid:173)
`network switching.
`
`See automatic emulation switching.
`
`In typesetting, a unit of measurement that equals half the
`of an em space, which is the width of the capital letter M
`a typeface. En dashes are used in place of the English words
`" or "through;' as in January 9-January 23 or Pages 63-68.
`ey also are used as minus signs, as in -30 degrees Fahrenheit.
`mpare to em dash.
`
`capsulated PostScript (EPS) file A high-resolution
`phic image stored in the PostScript page description lan-
`ge. The EPS standard enables users to transfer high-resolution
`hies images between applications. You can size EPS images
`out sacrificing image quality. A major drawback of EPS
`hies is that to print them, you usually need a PostScript(cid:173)
`patible laser printer. A second drawback is that with most
`lication programs, you cannot view the image onscreen
`ess you attach a screen image to it. To provide an alternative
`expensive PostScript printers, developers have created pro(cid:173)
`such as LaserGo, Inc.'s GoScript that interpret and print
`es on standard dot-matrL'\: printers or nonPostScript laser
`inters. See PostScript.
`
`capsulation
`In wide area networks (WANs), the process by
`hich transmitted data is altered as it moves down the comput(cid:173)
`protocol stack. As each layer's protocols alter the data, it is
`nslated into a form that can be sent out over the network. At
`receiving computer, this process is reversed so that the data is
`ored in such a form that it can be passed to an application
`d made intelligible to the user.
`
`encryption
`In cryptography, the process of converting a mes(cid:173)
`sage into a ciphertext (an encrypted message) by using a key so
`that the message appears to be nothing but gibberish. However,
`
`

`
`general format 235
`
`age characters
`In modems, meaningless characters
`by line noise. In printers, meaningless characters caused
`e noise, a faulty printer driver, or some other communica(cid:173)
`problem.
`
`age collection A process by which a program goes
`random access memory (RAM), decides which
`ation stored there is no longer needed, and prepares
`dresses housing the unneeded data for reuse. Garbage
`ction prevents programs from filling RAM with useless
`and causing a cras