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Macmillan Dictionary of Data Communications PDF

536 Pages·1985·63.768 MB·English
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OO&CC~ )])IICCilll@W~ @IF DATA COMMUNICATIONS Second Edition OOACCOOII111LA~ WIICCJTII@WAill~ (Q)JF DATA COMMUNICATIONS Second Edition CHARLES J. SIPPL M © The Macmillan Press Ltd, 1985 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No paragraph of this publication may be reproduced, copied, or transmitted save with written permission or in accordance with the provisions of the Copyright, Designs and Patents Act 1988, or under the terms of any licence permitting limited copying issued by the Copyright Licensing Agency, 33-4 Alfred Place, London WC1E7DP. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. First edition published 1976 Second edition first published 1985 by THE MACMILLAN PRESS LTD London and Basingstoke Associated companies in Auckland, Delhi, Dublin, Gaborone, Hamburg, Harare, Hong Kong, Johannesburg, Kuala Lumpur, Lagos, Manzini, Melbourne, Mexico City, Nairobi, New York, Singapore, Tokyo. Paperback reprinted 1991 British Library Cataloguing in Publication Data Sippi, Charles J. Dictionary of data communications. 1. Electronic data processing - case studies I. Title 001.6'03'21 QA76.15 ISBN 978-0-333-37083-4 ISBN 978-1-349-17845-2 (eBook) DOI 10.1007/978-1-349-17845-2 The paperback edition of this book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, resold, hired out, or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser. A A AND NOT 8 gate: A binary logic coinci absolute loader: A routine that uses abso dence (twoinput) circuit used to complete lute coding to load a program into memory the logic operations of A AND NOT B, i.e., at fixed numerical addresses. result is true only if statement A is true and statement B is false. absolute-value device: A transducer that produces an output signal equal in magni abend: Contraction for abnormal end. An tude to the input signal but always of one unexpected halt in a program due to a polarity. logical error, data that the program cannot process (such as division by zero, or the absolute-value sign: A sign using the sym addition of a number and a letter), or other bol as follows @abv indicating that the similar bugs. Abend, also referred to as absolute value of a number is to be taken, "bomb," is used as both a noun and a verb. i.e., the value of the number irrespective of the sign. abnormal end: See abend. abstract symbol: 1. (ISO) A symbol abnormal statement: An element of whose meaning and use have not been FORTRAN IV which specifies that certain determined by a general agreement but function subroutines must be called every have to be defined for each application of time they are referred to. Abnormal declar the symbol. 2. In optical character recogni ations enable the compiler to optimize the tion, a symbol whose form does not suggest calling of other (nonabnormal) function its meaning and use. These should be subroutines. defined for each specific set of applications. abort: A procedure to terminate execu ac bias (magnetic tape) : The alternating tion of a program when an irrecoverable current, usually of a frequency several times error, mistake, or malfunction occurs. higher than the highest signal frequency, that is fed to a record head in addition to the absolute alarm: An audio or visual alarm signal current. AC bias serves to linearize set off by the detection of a variable which the recording process and is used uni has exceeded high or low limit conditions. versally in analog recording. Generally, a large ac bias is necessary to achieve max absolute coding: Coding in the numeric imum long-wavelength output and linear language form acceptable to the computer ity, but a lower value of bias is required to arithmetic and control unit. obtain maximum short-wavelength output. absolute delay: The real-time interval ac communication: Light, radio waves, from the transmission to reception of a sound, and data-transmission signals in signal over a circuit. Also called transmis alternating-current (ac) form are all sion time or circuit delay. described in terms of frequencies. In these various transmission forms the instant absolute instruction: A particular com aneous amplitude of the signal at a given puter instruction which specifies completely point in time varies rapidly, in a manner a specific computer operation and is capable similar to the displacement of a string on a of absolute instruction causing the execu musical instrument. The rate of this fluctu tion of that operation. ation is referred to as the frequency and 1 2 ac coupled flip-flop is expressed in terms of cycles per second or access scan: A procedure for receiVmg hertz. The term "hertz" (abbreviated Hz) data from files by searching each data item has by international agreement replaced the until the desired one is obtained. earlier term "cycles per second," thus honoring one of the early pioneers in the access time: 1. The time interval between field of electrical transmission, Heinrich the instant at which a control unit initiates a Hertz. call for data and the instant delivery of the data is completed. Access time equals ac coupled flip-flop: A flip-flop made up of latency plus transfer time. 2. The time electronic circuits in which the active interval between the instant at which data elements, either tubes or transistors, are are requested to be stored and the instant at coupled with capacitors. which storage is started. accelerating anode: An electrode given a accounting checks: Refers to accuracy high positive potential to speed up the controls on input data that are based on moving electrons in the beam of a writing such accounting principles as control totals, tube. cross totals, or hash totals. acceleration time: The time between the accounting function: The system of keep interpretation of instructions to read or ing track of machine usage and recording it. write on tape and the transfer of informa tion to or from the tape into storage, or accounting machine: 1. A machine that from storage into tape, as the case may be. prepares accounting records. 2. A machine accentuation: A technique for emphasiz that reads data from external storage ing particular bands in an audio-amplifier. media, such as cards or tapes, and automa tically produces accounting records or tabu accept ion: An atom in a doped semicon lations, usually on continuous forms. ductor crystal which accepts an electron or gives up a hole. accumulator register: The part of the arithmetic unit in which the results of an acceptance cone: The imaginary cone at operation remain, and into which numbers the end of an optic fibre whose half-angle is are brought to and from storage. the angle of incidence of the core/cladding interface. Any beam of light entering the accumulator shift instruction: A com fibre that is inside this cone (at an angle less ter instruction which causes the contents of than the half-angle) will reflect and be an accumulator register to shift to the left or propagated inside the fibre to the other end. right. accepted signal call: Using data channel accuracy: 1. (ISO) A qualitative assess signalling transmission, a signal sent in a ment of freedom from error, a high assess backward direction indicating a specific call ment corresponding to a small error. 3. can be completed. (ISO) A quantitative measure of the magni tude of error, preferably expressed as a acceptor circuit: Tuned circuit responding function of the relative error, a high value of to a signal of one specific frequency. this measure corresponding to a small error. access arm: A part of a disc storage unit Contrast with precision. that is used to hold one or more reading and writing heads. accuracy control character: A specific character designed with a function to con access mode: Used in COBOL program trol a given block of data, to indicate if the ming, the name of a technique used to dataare in error, to indicate if they are to be obtain a record from, or to place a recording disregarded or whether they can or cannot in a file contained in a storage device. be represented on a particular device. active element 3 ACH: See automated clearinghouse. acoustic coupler: A device which provides the facility to transmit and receive messages ACK: See acknowledgment. using the standard telephone handset as the coupling to the line. ACK (ARPANET): A short transmission between interface message processors acoustic delay line: A device used to store (IMP) to indicate the successful reception digital information cyclically in the form of of a message segment (referred to as a sound pulses. It consists of (1) a piezoelec packet). tric transmitter which converts normal digital information into an acoustic wave, ACKO, ACKl, Affirmative, Acknowledg (2) the acoustic transmission path, and (3) a ment: These replies indicate the previous piezoelectric receiving unit which converts block was accepted without error and the the acoustic data back into its original form. receiver is ready to accept the next block. Alternating these replies assists in the acoustic-sonic storage: Sonic delay line error-recovery procedures ACK1 is the storage types and techniques. response to the first transmission and suc cessive odd blocks. ACKO is the response to acquisition time: The interval time a the second block and all even-numbered sample-hold circuit needs to acquire the blocks, and is the positive response to input signal to within the stated accuracy. In selection (multipoint) or line bid (point-to conservative specifications, it includes the point) (BSC). settling time of the output amplifier. In some cases a signal can be acquired fully acknowledgment (ACK): In data trans (and the circuit switched into hold) before mission, data are usually grouped into the output has settled. The output of the fixed-length blocks. After transmitting a sample-hold is not meaningful until it has data block, the transmitting terminal sends settled. a check character, calculated from the con tent of the data block. The receiving termi action line: When a cathode ray storage nal compares this character with its own tube is operating in a serial mode, it refers computation of the check character. If the to that tine of the raster which is used during values agree, then no transmission error has the active period. occurred and the receiving terminal sends the control character ACK to the trans mitter to signify that no error occurred. The action spot: The spot of the raster on the transmitting terminal then continues trans face of an electrostatic storage tube which mission of another data block. If the check stores the digits and holds a charge. characters differ, then an error occurred and the receiver sends a NAK (negative activate key (button): A primary switch on acknowledgment) character to indicate an various control panels which when pressed error to the transmitter. The transmitter or initiated will cause the first part or step of then repeats transmission of the same data a program cycle or a procedure to begin. block and the process repeats. Same as Same as start key (button or switch) and acknowledge character. initiate button. acknowledgment character (AKC): A active element: 1. An element in use or in specific character for communications con its excited state, i.e., a tube, transistor or trol transmitted in an affirmative response device which is on or alive rather than off, from a message-receiving program. Most dead or in a ground state. 2. A file, record, often used as an accuracy control character or routine which is being used contacted, or transmitted after a string of characters has referred to. Computing components are been received with proper vertical and active when they are directed by the control longitudinal redundancy check characters. unit. 4 active me active me: A file which is being used in adaptive tree walk protocol: A limited which entries or references are made on a contention protocol with stations organized current basis. in a binary tree. active intruder: An intruder who can add time (in microseconds): The time record messages to hear later, send his own required to acquire from memory and exe messages on the desired communication cute one fixed-point add instruction using channel, or alter legitimate messages before all features such as overlapped memory they reach the intended receiver. banks, instruction look-ahead and parallel execution. active master file: A specific master file add-to-storage concept: The process in that contains items relatively active or which the sum of two numbers is calculated frequently used as contrasted to static or by adding the first number to the second and reference items. the results replace the second number (all in one operation). active master item: The most active items on a master file by usage data. adder-subtracter: (ISO) A device that acts as an adder or subtracter depending active network: A electronic network upon the control signal received. The which contains any sources of power other adder-subtracter may be constructed so as than signal inputs. to yield the sum and the difference at the same time. active state: The state of an interrupt level that is the result of the central processor addition without carry: A logical opera starting to process an interrupt condition. tion applied to two operands that produce a result relying on the bit patterns of the active transducer: Any transducer in operands and according to rules for each bit which the applied power controls or modu position. lates locally supplied power, which becomes the transmitted signal, as in a additional character: A character which is modulator, radio transmitter. neither a letter nor a number, but which is usually a punctuation mark,%,-,#; i.e., activity level: The value taken by a struc a member of a specialized alphabet. A specific meaning is assigned to this charac tural variable in an intermediate or final solution to a programming problem. ter to use it to convey special information. additional label processing: The use of the actuating signal: A particular input pulse input/output label system to verify or create in the control circuitry of computers. a standard label and then, by user's routines, verify or insert additional ADAPSO: An association of U.S. and information in the optional field of the Canadian data processing service organ standard label. izations. address: 1. A character or group of add-on: Hardware attached to a computer characters that identifies a register, a parti to increase performance or memory. cular part of storage, or some other data source or destination. 2. To refer to a device add/subtract time: The time required to or an item of data by its address. perform an addition or subtraction, exclu sive of the time required to obtain the address, control data, and cbeeksulll quantities from storage and put the sum or ftelds: Four kinds of fields in bit oriented difference back into storage. protocol frames. AFIPS 5 address comparator: A device used to location where the address of the operand verify that the correct address is being read. may be found. The comparison is made between the address being read and the specified adjacent channel: The channel whose fre address. quency band is adjacent to that of the reference channel. address conversion: The translation of the adjacent channel interference: The pres relative or symbolic addresses into absolute ence of undesirable energy in a channel addresses by use of a computer, or caused by one or both sidebands of modu manually. lated carrier channels in close frequency proximity extending from one into another address field: The portion of an instruc through electrostatic or electromagnetic tion word that contains the operand coupling. address. adjoint system: A method of computation address format: 1. The arrangement of based on the reciprocal relation between a the address parts of an instruction. The system of ordinary linear differential equa expression "plus-one" is frequently used to tions and its adjoint. indicate that one of the addresses specifies the location of the next instruction to be administrative data processing: An ex executed. Such as one-plus-one, two-plus pression usually meaning business data pro one, threeplus-one, four-plus-one. 2. The cessing such as the recording, classifying, or arrangement of the parts of a single address summarizing of transactions, activities, such as those required for identifying chan events, etc. Usually of a financial nature, or nel, module, track, etc. in a disk system. the collection, retrieval, or control of such items. address generation: A number or symbol generated by instructions in a program and admissible mark: Specific rules or con used as an address part, i.e., a generated ventions determine which marks, symbols, address. and numerals or characters are permitted in various areas of computing for all install address immediate instruction: Specific ations and for various languages. instructions designed to contain the value of the operand in its address part rather than advanced data communication control pro cedure (ADCCP): A version of synchro the address of the operand. It is used most often for incrementing a count by a fixed nous data link control (SDLC) modified by amount or masking a partial-word field of the American National Standards Institute data, or for testing a special character for (ANSI). identical characteristics with the immediate Advanced Research Project Agency Net· character in the instruction. work (ARPANET): The long-haul com munications network maintained by an address register: A register in a computer agency (ARPA) of the United States Fed where an address is stored. eral Government. ARPANET is one of America's most important networks addressing level: A determination of the because it links not only government number of steps of indirect address which computers, but research computers at have been applied to a particular program. virtually every major American university First level is direct addressing, i.e., the as well. address part of the instruction word has the address of the operand in storage. In second AFIPS: An organization of computer level addressing (indirect), the address part related societies. Its members include: The of the instruction word gives the storage Association for Computer Machinery; The 6 air movement data Institute of Electrical and Electronic algorithm: A prescribed set of well Engineers Computer Group; Simulation defined rules or processes for the solution of Councils, Inc.; American Society for a problem in a finite number of steps, for Information Science. Its affiliates include: example, a full statement of an arithmetic American Institute of Certified Public procedure for evaluating sin x to a stated Accountants; American Statistical Associ precision. Contrast with heuristic. ation; Association for Computational Linguistics; Society for Industrial and algorithm translation: A specific, effec Applied Mathematics; Society for Informa tive, essentially computational method for tion Display. Headquarters-Montvale, N.J. obtaining a translation from one language to another. agenda: The set of control-language statements used to prescribe a solution path algorithmic language (computer): An or run procedures; an ordered list of the arithmetic language by which numerical major operations constituting a procedure procedures may be precisely presented to a for a solution or computer run. (This usage computer in a standard form. The language corresponds roughly to the ordinary is intended not only as a means of directly "agenda" for a meeting.) presenting any numerical procedure to any suitable computer for which a compiler agent: A process whose job is to provide a exists, but also as a means of communicat uniform interface to all hosts in a network ing numerical procedures among individ operating system. uals. The language itself is the result of international cooperation to obtain a stan air movement data: Data presented most dardized algorithmic language. The Inter often with digital displays relating to flight national Algebraic Language is the forerun plan information such as present position, ner of ALGOL. future position, estimated time of arrival, algorithmic routine: That specific routine etc. which directs the computer in a program to solve a problem in a finite or specified alertor: A device which consists of a small number of steps, but not rely on a trial and box connected to a large floor pad laced error procedure. The solution and solution with with wires. It sounds an alarm when method are exact and must always reach the the operator has not operated the pad for a specific answer. specific period of time. alias: 1. An alternate label. For example, algebraic language: An algorithmic lan a label and one or more aliases may be used guage many of whose statements are struc to refer to the same data element or point in tured to resemble the structure of algebraic a computer program. 2. An alternate name expression, e.g., ALGOL, FORTRAN. for a member of a partitioned data set. 3. In pulse code modulation telecommunication ALGOL (ALGOrithmic Language): An links, a spurious signal resulting from beats international algebraic procedural language between the signal frequencies and the for a computer programming system. sampling frequency. ALGOL-Dartmouth: The Dartmouth alien tones: Frequencies, harmonics and ALGOL is essentially ALGOL-60 with other products introduced in sound repro only a few restrictions and extensions made duction because of nonlinearity in some to allow operation within the BASIC part of the transmission path. system timesharing framework. alignment: See boundary alignment. algoristic: A step-by-step methodology; an exact answer; a systematic computation allocate storage: To assign storage loca guaranteeing accurate solution. tions or areas of storage for specific

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