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`Cisco v. TQ Delta
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`CSCO-1018
`Cisco v. TQ Delta
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`This dictionary is one of a series
`dents of computer science, but we
`and to anyone who uses computer
`in the series are The Facts On File
`nary of Chemistry, The Facts On
`tionary of Mathematics, The Fac
`Facts On File Dictionary of Astra
`
`This book is based on a Minidictix
`Oxford University Press in 1986 a
`dictionary now contains over 230
`computer science. An extensive A
`bols, file extensions, domain nam«
`
`We would like to thank all the pec
`A list of contributors is given on t]
`the many people who have given :
`
`The Facts On File Dictionary of Computer Science
`
`Fourth Edition
`
`Copyright © 2001 by Market House Books Ltd
`
`All rights reserved. No part of this book may be reproduced or utilized in any
`form or by any means, electronic or mechanical, including photocopying,
`recording, or by any information storage or retrieval systems, without
`permission in writing from the publisher. For information contact:
`
`Checkmark Books
`An imprint of Facts On File, Inc
`11 Penn Plaza
`New York NY 10001
`
`Library of Congress Cataloging-in-Publication Data
`The Facts on File dictionary of computer science. / [edited by]
`Valerie Illingworth and John Daintith.
`p.
`cm.
`2 acid-free paper)
`ISBN 0-8160-4285-3 (he.
`.: ;acid—free paper)
`ISBN 0-8160-4286-1 (pbk.
`1. Computer Science—Dictionaries.
`I. Illingworth, Valerie.
`John.
`III. Facts on File, Inc.
`IV. Title: Dictionary
`of computer science.
`QA76.15 F345 2000
`004‘.03—dc2l
`
`00-055555
`
`II Daintith,
`
`Checkmark Books are available at special discounts when purchased in bulk
`quantities for businesses, associations, institutions, or sales promotions. Please call
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`
`Compiled and typeset by Market House Books Ltd, Aylesbury, UK
`
`Cover design by Cathy Rincon
`
`Printed in the United States of America
`
`765431
`765431
`
`This book is printed on acid-free paper
`
`Page 2 of 4
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`

`
`logic OPERANDS have to be placed in a spe-
`cial register called the ACCUMULATOR, while
`in other processors any register may be
`used. The result of the operation is subse—
`quently transferred back to the main store.
`The movement of data between main store
`and ALU is under the direction of the CON-
`TROL UNIT. The arithmetic or logic opera-
`tions to be performed in the ALU are
`specified in the operation part of MACHINE
`INSTRUCTIONS. The control unit interprets
`each instruction as it is fetched from main
`store and directs the ALU as to which op-
`eration (if any) is required.
`
`arithmetic instruction A machine in-
`struction specifying an ARITHMETIC OPERA-
`TION and the OPERAND or operands on p
`which the arithmetic operation is to be per-
`formed. An example, expressed in ASSEM-
`ELY LANGUAGE, might be
`ADDI 3 4
`This is an instruction to add 4 to contents
`of register 3, placing the result in register 3
`and setting the carry bit if the result is too
`big to fit.
`See also logic instruction.
`
`arithmetic/logic unit
`and logic unit.
`
`See arithmetic
`
`arithmetic operation An operation
`that follows the rules of arithmetic,
`the
`most commonly occurring examples being
`addition, subtraction, multiplication, and
`division. In computing, arithmetic opera-
`tions may be carried out on signed or un-
`signed INTEGERS or REAL NUMBERS. They are
`normally performed in the ARITHMETIC AND
`LOGIC UNIT of a computer. See also arith-
`metic operator; operand.
`
`arithmetic operator A symbol repre-
`senting a simple arithmetic operation (e.g.
`addition or multiplication) that is to be
`performed on numerical data, quantities,
`etc. The operators used in a particular pro-
`gramming language may differ from those
`in general use, as shown in the table. The
`operations i
`
`7 multiplied by 2
`6 divided by 3
`
`ARITHMETIC OPERATORS
`
`Operators
`
`In general use
`+
`
`In Basic
`+
`
`Operation
`
`addition
`
`subtraction
`
`multiplication
`division
`
`exponentiation
`
`would thus be written as 7=»Z and 6/3 in
`most high—level languages. Some languages
`have separate operators for integer division
`and remaindering (see integer arithmetic).
`Some languages do not have an operator
`for EXPONENTIATTON.
`A11 example of how arithmetic opera-
`tors are used, in Basic, is as follows:
`10
`D = SQR((X(1) — X(0)) T 2 +
`X(2)>i-3)
`This is equivalent to
`D = v(<Xi — X0? + 3X2)
`
`arithmetic shift
`
`See shift.
`
`arithmetic unit
`logic unit.
`
`See
`
`arithmetic
`
`and
`
`ARI’
`
`See address resolution protocol.
`
`ARPANET (Advanced Research Project
`Agency Network) A network introduced
`in 1969 connecting a small number of re-
`search institutions, funded by the US De-
`partment of Defense. ARPANET used
`PACKET SWITCHING and pioneered many of
`the protocols used in network operation. It
`was the forerunner of the INTERNET.
`
`array One form in which a collection of
`data items can be stored in computer mem-
`ory. The data items
`in an array are
`arranged in a particular order or pattern
`and are all of the same type, for example all
`integers or all real numbers. This collection
`of data items is referred to as an array.
`More usually, however,
`the word array
`
`refers to the set of storage LOCATIONS in
`which the data items are placed, keeping
`their original arrangement.
`The set of locations forming an array is
`referenced by a single IDENTIFIER, chosen by
`the programmer. Each element in an array
`(i.e. a location or its contents) can be spec-
`ified by combining one or more subscript
`values with the identifier. Subscripts are
`usually integers and are generally placed in
`brackets after the identifier. The number of
`subscripts required to specify an element
`gives the dimension of the array.
`The simplest array is a single sequence
`of elements. This is a one-dimensional
`army, only one subscript being necessary
`to select a particular element. For example,
`a list of peoples’ ages could form an array
`named AGE; the age of the eighth person in
`the list is found by specifying AGE(8). The
`subscript may be a VARIABLE. A one—dimen—
`sional array is also known as a vector.
`In a two-dimensional array (also called
`a matrix), the elements are arranged in the
`form of a table with a fixed number of
`rows and a fixed number of columns. Each
`element is distinguished by a pair of sub-
`scripts;
`the first subscript gives the row
`number, the second gives the column num-
`ber. For example, A(3 7) refers to the ele-
`ment in row three and column seven of the
`array A. Again, the subscripts may be vari-
`ables.
`,
`The values of a subscript range from a
`lower limit (usually 1 or 0 unless otherwise
`specified) to an upper limit. These limits
`specify the total number of elements in an
`
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