Table Of Content

DICTIONARY OF COMPUTER SCIENCE, ENGINEERING, AND TECHNOLOGY EDITOR-IN-CHIEF Phillip A. Laplante CRC Press Boca Raton London New York Washington, D.C. Library of Congress Cataloging-in-Publication Data Dictonary of computer science, engineering, and technology / edited by Phillip Laplante. p. cm. Includes bibliographical references and index. ISBN 0-8493-2691-5 (alk. paper) 1. Computer science—Dictionaries. 2. Engineering—Dictionaries. 3. Technology—Dictionaries. I. Laplante, Phillip A. QA76.15.D5258 2000 004'.03—dc21 00-052882 This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. All rights reserved. Authorization to photocopy items for internal or personal use, or the personal or internal use of specific clients, may be granted by CRC Press LLC, provided that $.50 per page photocopied is paid directly to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923 USA The fee code for users of the Transactional Reporting Service is ISBN 0-8493-2691-5/01/$0.00+$.50. The fee is subject to change without notice. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Visit the CRC Press Web site at www.crcpress.com © 2001 by CRC Press LLC No claim to original U.S. Government works International Standard Book Number 0-8493-2591-5 Library of Congress Card Number 00-052882 2 3 4 5 6 7 8 9 0 PREFACE One can only appreciate the magnitude of effort required to develop a dictionary by actually experiencing it. Although I had written nine other books, I certainly did not know what I was getting into when in January of 1996 I agreed to serve as Editor-in-Chief of CRC Press's Comprehensive Dictionary of Electrical Engineering. Published 2 1/2 years later in 1999,1 finally understood what I had gotten myself into. Unlike other books that I had written, creating that dictionary was more a test of will and stamina and an exercise in project management than in mere writing. And although I have managed organizations of up to 80 academics, nothing is more like "herding cats" than motivating an international collection of more than 100 distinguished engineers, scientists, and educators scattered around the globe, almost entirely via email. Yet, I think there is no other way to develop a dictionary. I still marvel at how Noah Webster must have managed to construct his English Dictionary without the benefits of modern communication. But I learned many lessons from the Electrical Engineering Dictionary project that made the development of this dictionary far easier. For example, I put the development schedule on a much faster track, and I didn't burden the contributors with excessive formatting guidelines. Neverthe- less, like the Electrical Engineering Dictionary, this dictionary, as much as it is an organizational achievement, is really the collaborative work of many brilliant and dedicated men and women. This is their dictionary and your dictionary. I hope you refer to it regularly and enjoy it. Phillip A. Laplante, PE, Ph.D. Editor-in-Chief President Pennsylvania Institute of Technology Media, Pennsylvania FOREWORD How Was the Dictionary Constructed As I knew this project would require a divide-and-conquer approach with fault-tolerance, I sought to partition the dictionary by defining areas that covered all aspects of Computer Science, Computer Engineering, and Computer Technology. The partitions I selected were based largely on the Denning report on the Computer Science Curriculum (Peter Denning, et al, "Computing as a Discipline," IEEE Computer Journal, 22,63-70, Feb. 1989), with some additions. The partitioning was made with intentional overlap, since I knew that many terms needed to be defined several different ways depending on usage, and I needed to ensure that every term would be defined at least once. The resultant areas were: • Algorithms, Data Structures, and Problems • Artificial Intelligence • Communications and Information Processing • Computer Engineering (Processors) • Computer Engineering (I/O and Storage) • Computer Graphics • Database Systems • Numerical Computing • Operating Systems • Programming Languages • Software Engineering • Robotics and Synthetic Environments • Computer Performance Analysis While sufficient hardware terms were included to understand the basics of digital electronics, those interested in additional electrical engineering terms should consult CRC's Comprehensive Dictionary of Electrical Engineering which includes many more such terms. Given the area editor structure, constructing the dictionary then consisted of the following steps: 1. Creating a terms list for each area 2. Defining terms in each area 3. Cross-checking terms within areas 4. Cross-checking terms across areas 5. Compiling and proofing the terms and definitions 6. Reviewing the compiled dictionary 7. Final proofreading The first and most important task undertaken by the area editors was to develop a terms list to be defined. A terms list is a list of terms (without definitions), proper names (such as important historical figures or companies), or acronyms relating to their areas. What went into each terms list was left to the discretion of the area editor based on the recommendations of the contributing authors. However, lists were to include all technical terms that related to the area (and subareas). Technical terms of an historical nature were only included if it was noted in the definition that the term is "not used" in modern engineering or that the term is "historical" only. Although the number of terms in each list varied somewhat, each area's terms list consisted of approximately 700 items. The dictionary includes contributions from over 100 contributors from 17 countries. Once the terms lists were created, they were merged and scrutinized for any obvious omissions. These missing terms were then picked up from other sources including CRC handbooks and dictionaries. These included The Control Handbook, Electronics Handbook, Image Processing Handbook, Circuits and Filters Handbook, and The Electrical Engineering Handbook. About 1000 terms were taken from the CRC handbooks. We also borrowed, with permission from IEEE, about 40 definitions that could not be found elsewhere or could not be improved upon. The process of developing and collecting the terms took 1 1/2 years. Once all of the terms and their definitions were collected, the process of converting, merging, and editing began. This process took an additional six months. Although authors were provided with a set of guidelines to write terms definitions, they were free to exercise their own judgment and to use their own style. As a result, the entries vary widely in content from short, one-sentence definitions to rather long dissertations. While I tried to provide some homogeneity in the process of editing, I neither wanted to tread on the feet of the experts and possibly corrupt the meaning of the definitions, nor did I want to interfere with the individual styles of the authors. As a result, I think the dictionary contains a diverse and rich exposition that collectively provides good insights into the areas intended to be covered by the dictionary. Moreover, I was pleased to find the resultant collection much more lively, personal, and user-friendly than typical dictionaries. But despite the incredible support from my area editors, individual contributors, and staff at CRC Press, the final task of arbitrating conflicting definitions, rewording those that did not seem descriptive enough, and identifying missing ones was left to me. I hope that I have not failed you in my task. How to Use the Dictionary The dictionary is organized like a standard language dictionary except that not every word is defined (this would necessitate a complete embedding of an English dictionary). However, I tried to define most nonobvious technical terms used in the definition of another term. In some cases, more than one definition is given for a term. These are denoted (1), (2), (3), ..., etc. Multiple definitions were given in cases where the term has multiple distinct meanings in differing applications areas, in which case the definition is preceded by an identifier (e.g., "in robotics") to indicate the relevant area, except when the area is obvious or readily determined from the definition itself. When more than one equivalent but uniquely descriptive definition was available, to help increase understanding I included both. In most cases, the possible definitions are ordered according to their most likely usage. But I leave it to the reader to pick the definition that seems to fit your situation most closely. The notations 1., 2., etc. are used to itemize certain elements of a definition and are not to be confused with multiple definitions. All noun terms are defined in the singular form, except for collective nouns or where the singular form is not used. Acronym terms are listed by their expanded name. Under the acronym the reader is referred to that term. For example, if you look up "RISC" you will find "See reduced instruction set computer," where the definition can be found. The only exceptions are in the cases where the expanded acronym might not make sense, or where the acronym itself has become a word (such as "Fortran" or "Basic"). Finally, I tried to avoid proprietary names and trade names where possible. Some crept in because of their importance, however. Acknowledgments A project of this scope literally requires hundreds of participants. I would like to take this moment to thank these participants both collectively and individually. I thank, in no particular order: • The editorial board members and contributors. • Ron Powers, CRC President of Book Publishing, for conceiving this dictionary and believing in me. • Nora Konopka, Acquisitions Editor from CRC, for providing incredible editorial support. • The many other people at CRC who provided all kinds of support in the development and production of this book. • My wife Nancy for converting, typing, and/or entering many of the terms. • Susan Fox for providing excellent copy editing of the final manuscript. This achievement is as much theirs as it is mine. Please accept my apologies if anyone was left out — this was not intentional and will be remedied in future printings of this dictionary. Finally, thank you to my wife Nancy and children Christopher and Charlotte for their incredible patience and endurance while I literally spent hundreds of hours giving birth to this dictionary. How to Report Errors/Omissions Because of the magnitude of this undertaking and because I attempted to develop new definitions completely from scratch, I have surely omitted (though not deliberately) many terms. In addition, some definitions are possibly incomplete, weak, or even incorrect. I want to evolve and improve this dictionary in subsequent printings and editions. You are encouraged to participate in this collaborative, global process. Please send any suggested corrections, improvements, or new terms (along with suggested definitions) to me at EDITOR-IN-CHIEF Phil Laplante is President of the Pennsylvania Institute of Technology, a two-year, private college that focuses on technology training and re-training. Prior to this, he was the founding dean of the BCC/NJIT Technology and Engineering Center in Southern New Jersey. He was also Professor of Computer Science and Chair of the Mathematics, Computer Science, and Physics Department at Fairleigh Dickinson University, New Jersey. In addition to his academic career, Dr. Laplante spent almost eight years as a software engineer designing avionics systems, a microwave CAD engineer, a software systems test engineer, and a consultant. He has written dozens of articles for journals, newsletters, magazines, and conferences, mostly on real-time computing and image processing. He has authored 13 other technical books and co-founded the journal Real-Time Imaging, as well as two book series including the CRC Press Series on Image Processing. Dr. Laplante received his B.S., M. Eng., and Ph.D. in Computer Science, Electrical Engineering, and Computer Science, respectively, from Stevens Institute of Technology and an MBA from the University of Colorado. He is a senior member of IEEE and a member of numerous other professional societies, program committees, and boards. He is a licensed professional engineer in New Jersey and Pennsylvania and actively consults to high-tech start-ups, established technology firms, investors, and venture capitalists on technology and business strategy. Dr. Laplante is married with two children and resides in Pennsylvania.