IBM DICTIONARY
`OF COMPUTING
`
`Compiled and edited by
`" GEORGE MCDANIEL
`
`
`
`MCGRAW-HILL, INC.
`New York San Francisco Washington, i.'J.C. Auckland Bogota
`Caracas Lisbon London Madrid Mexico City Milan
`Montreai New Delhi San Juan Singapore
`Sydney Tokyo Toronto
`
`

`
`While the Editor and Pubiisher of this book have made reasonable efforts to
`ensure the accuracy and timeliness of the information contained herein, nei-
`ther the Editor nor the Publisher shall have any liability with respect to loss or
`damage caused or alleged to be caused by reliance on any information con-
`tained herein.
`
`Copyright © 1994 by International Business Machines Corporation. All rights
`reserved. Printed in the United States of America. Except as permitted under
`the United States Copyright Act of 1976, no part of this publication may be
`reproduced or distributed in any form or by any means, or stored in a data
`base or retrieval system, without the prior written perrnisssion of the pub-
`lisher.
`’
`
`1234567890 DOC/DOC 99876543
`
` Limitation of Liability
`
`ISBN 0—07—O31488-8 (HC)
`ISBN 0-07~03-I489-6 (PBK)
`
`The sponsoring editor for this book was Daniel A. Gonneau and the
`production supervisor was Thomas G. Kowalczyk.
`
`Printed and bound by R. R. Donnelley & Sons Company.
`
`Tenth Edition (August 1993)
`
`This is a major revision of the IBM Dictionary of Computing, SC20-1699-8,
`which is made obsolete by this edition. Changes are made periodically to the
`information provided herein.
`
`It is possible that this material may contain reference to, or information about,
`IBM products (machines and programs), programming, or services that are
`not announced in your country. Such references or information must not be
`construed to mean that IBM intends to announce such IBM products, pro-
`gramming, or services in your country. Cornments may be addressed to IBM
`Corporation, Department E37/656, P. O. Box 12195, Research Triangle Park,
`NC27709.
`
`International Edition
`
`Copyright © 1994 by International Business Machines Corporation. Exclusive
`rights by McGraw«I-Iill, Inc. for manufacture and export. This book cannot be
`re-exported from the country to which it is consigned by McGraw-Hill. The
`International Edition is not available in North America.
`
`When ordering this title, use ISBN 0-07-113383—6.
`
`This book is printed on acicbfree paper.
`
`
`
`

`
`round down
`
`[588]
`
`_______K
`
`routine
`
`tied rule. The purpose of rounding is usually to limit
`the precision of a numeral or to reduce the number of
`characters in the numeral, or both. The most common
`forms of rounding are rounding down, rounding up,
`and rounding off.
`(I)
`(A)
`(2) Contrast with trun-
`cation.
`
`(A)
`(I)
`become 12.64 and 15.07, respectively.
`(2) On a calculator, the increase by one of the least
`significant digit
`in the result of a calculation if the
`highest decimal place dropped off has a value of more
`than zero. (T)
`
`
`
`route An ordered sequence of nodes and trans-
`mission groups (TGs) that represent a path from an
`origin node to a destination node traversed by the
`traffic exchanged between them.
`
`route addition resistance (RAR) A value that indi.
`cates a network node's capacity to perfonn interme_
`diate session routing.
`
`the path control
`route extension (REX) In SNA,
`network components, including a peripheral link, that
`make up the portion of a path between a subarea node
`and a network addressable unit (NAU) in an adjacent
`peripheral node.
`See also explicit route (ER), path,
`virtual route (VR).
`
`router (I) A computer that determines the path of
`network traffic flow. The path selection is made from
`several paths based on information obtained from spe-
`cific protocols, algorithms that attempt to identify the
`shortest or best path, and other criteria such as metrics
`or protocol-specific destination addresses.
`(2) An
`attaching device that connects two LAN segments,
`which use similar or different architectures, at the ref-
`erence mcdel network layer. Contrast with bridge,
`gateway.
`(3)
`In OSI terminology,
`a- function that
`determines a path by which an entity can be reached.
`(4) See Internet router.
`
`Route Selection control vector (RSCV) A control
`vector that describes a route within an APPN network.
`The RSCV consists of an ordered sequence of control
`vectors that identify the TGs and nodes that make up
`the path from an origin node to a destination node.
`
`route selection services (RSS) A subcomponent of
`the topology and routing services component
`that
`determines the preferred route between a specified pair
`of nodes for a given class of service.
`
`Route Table Generator (RTG) IBM-supplied field
`developed program that assists the user in generating
`path tables for SNA networks.
`
`route weight A value computed for the set of TGs
`and intermediate nodes interconnecting an origin and
`destination node; route weight determines which route
`is preferred during the route selection process.
`
`that
`routine (1) A program, or part of a program,
`may have some general or frequent use. (T)
`(2) In
`REXX, a series of instructions called with the CALL
`instruction or as a function. A routine can be either
`internal or external
`to a user’s program.
`(3) See
`
`
`
`round down (1) To round, making no adjustment to
`the part of numeral retained.
`If a numeral is rounded
`down, its absolute value is not increased. Rounding
`down is a form of truncation;
`for example, numerals
`12.6374 and 15.0625, when rounded down to two
`decimal
`places,
`become
`12.63
`and
`15.06,
`respectively. (I)
`(A)
`(2) On a calculator, elimi-
`nation in result of a calculation of all digits beyond
`least significant digit. (T)
`
`rounding error (1) An error due to rounding.
`(A)
`(2) Contrast with truncation error.
`
`(I)
`
`round off (1) To round, adjusting part of numeral
`retained by adding I
`to die least significant of its
`digitsand executing any necessary carries, if and only
`if the most significant of digits deleted is equal to or
`greater than half the radix of its digit place;
`for
`example,
`numerals
`12.6375
`and
`15.0625, when
`rounded off to two decimal places, become 12.64 and
`15.06,
`respectively.
`(I)
`(A)
`(2) On a calculator,
`increase of the least significant digit in result of a cal-
`culation to the next higher number where the subse-
`quent digit
`in result
`is
`5 or above. Where the
`subsequent digit
`is 4 or below,
`the least significant
`digit remains unchanged. (T)
`
`operating
`the OS/2
`scheduling In
`round-robin
`system, a process that allows each thread to run for a
`specified amount of time.
`
`round-trip message delay The sum of the one-way
`message delays from the origin to the destination and
`back, not including application processing time.
`
`round-trip propagation time Twice the time required
`for a bit to travel between the two most distant data
`stations in a bus network.
`
`In a network using carrier sense, each trans-
`Note:
`mission frame must be long enough so that a collision
`or jam signal may be detected by the transmitting
`station while this transmission frame is being trans-
`mitted.
`lts min.imum length is therefore determined by
`the round-trip propagation time.
`(T)
`
`round up (1) To round, adjusting the part of the
`numeral that is retained by adding 1 to the least signif-
`icant of its digits and executing any necessary carries,
`if and only if one or more nonzero digits have been
`deleted.
`If a numeral is rounded up, its absolute value
`is not decreased;
`for example, the numerals 12.6374
`and 15.0625, when rounded up to two decimal places,