Linda Null and Julia Lobur
JONES AND BARTLETT COMPUTER SCIENCE
the essentials of
Pennsylvania State University
Pennsylvania State University
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Copyright © 2003 by Jones and Bartlett Publishers, Inc. Cover image © David Buffington / Getty Images Illustrations based upon and drawn from art provided by Julia Lobur Library of Congress Cataloging-in-Publication Data Null, Linda. The essentials of computer organization and architecture / Linda Null, Julia Lobur. p. cm. ISBN 0-7637-0444-X 1. Computer organization. 2. Computer architecture. I. Lobur, Julia. II. Title. QA76.9.C643 N85 2003 004.2’2—dc21 2002040576 All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilized in any form, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without written permission from the copyright owner. Chief Executive Officer: Clayton Jones Chief Operating Officer: Don W. Jones, Jr. Executive V.P. and Publisher: Robert W. Holland, Jr. V.P., Design and Production: Anne Spencer V.P., Manufacturing and Inventory Control: Therese Bräuer Director, Sales and Marketing: William Kane Editor-in-Chief, College: J. Michael Stranz Production Manager: Amy Rose Senior Marketing Manager: Nathan Schultz Associate Production Editor: Karen C. Ferreira Associate Editor: Theresa DiDonato Production Assistant: Jenny McIsaac Cover Design: Kristin E. Ohlin Composition: Northeast Compositors Text Design: Anne Flanagan Printing and Binding: Courier Westford Cover Printing: Jaguar Advanced Graphics This book was typeset in Quark 4.1 on a Macintosh G4. The font families used were Times, Mixage, and Prestige Elite. The first printing was printed on 45# Highland Plus. Printed in the United States of America 07 06 05 04 03 10 9 8 7 6 5 4 3 2 1
In memory of my father, Merrill Cornell, a pilot and man of endless talent and courage, who taught me that when we step into the unknown, we either find solid ground, or we learn to fly. —L. M. N. To the loving memory of my mother, Anna J. Surowski, who made all things possible for her girls. —J. M. L.
TO THE STUDENT
Tfunction and design of the various components necessary to process informa-
his is a book about computer organization and architecture. It focuses on the
tion digitally. We present computing systems as a series of layers, starting with low-level hardware and progressing to higher-level software, including assemblers and operating systems. These levels constitute a hierarchy of virtual machines. The study of computer organization focuses on this hierarchy and the issues involved with how we partition the levels and how each level is implemented. The study of computer architecture focuses on the interface between hardware and software, and emphasizes the structure and behavior of the system. The majority of information contained in this textbook is devoted to computer hardware, and computer organization and architecture, and their relationship to software performance. Students invariably ask, “Why, if I am a computer science major, must I learn about computer hardware? Isn’t that for computer engineers? Why do I care what the inside of a computer looks like?” As computer users, we probably do not have to worry about this any more than we need to know what our car looks like under the hood in order to drive it. We can certainly write high-level language programs without understanding how these programs execute; we can use various application packages without understanding how they really work. But what happens when the program...