write great code volume 1

www.it-ebooks.info www.it-ebooks.info WRITE GREAT CODE Volume I: Understanding the Machine by Randall Hyde San Francisco www.it-ebooks.info WRITE GREAT CODE. Copyright © 2004 by Randall Hyde. All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. Printed on recycled paper in the United States of America 1 2 3 4 5 6 7 8 9 10 – 07 06 05 04 No Starch Press and the No Starch Press logo are registered trademarks of No Starch Press, Inc. Other product and company names mentioned herein may be the trademarks of their respective owners. Rather than use a trademark symbol with every occurrence of a trademarked name, we are using the names only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. Publisher: William Pollock Managing Editor: Karol Jurado Cover and Interior Design: Octopod Studios Developmental Editor: Hillel Heinstein Technical Reviewer: Mark de Wever Copyeditor: Andy Carroll Compositor: Riley Hoffman Proofreader: Stephanie Provines For information on book distributors or translations, please contact No Starch Press, Inc. directly: No Starch Press, Inc. 555 De Haro Street, Suite 250, San Francisco, CA 94107 phone: 415-863-9900; fax: 415-863-9950; info@nostarch.com; http://www.nostarch.com The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has been taken in the preparation of this work, neither the author nor No Starch Press, Inc. shall have any liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the information contained in it. Library of Congress Cataloguing-in-Publication Data Hyde, Randall. Write great code : understanding the machine / Randall Hyde. p. cm. ISBN 1-59327-003-8 1. Computer programming. 2. Computer architecture. I. Title. QA76.6.H94 2004 005.1 dc22 2003017502 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info BRIEF CONTENTS Chapter 1 What You Need to Know to Write Great Code 1 Chapter 2 Numeric Representation 9 Chapter 3 Binary Arithmetic and Bit Operations 39 Chapter 4 Floating-Point Representation 65 Chapter 5 Character Representation 103 Chapter 6 Memory Organization and Access 133 Chapter 7 Composite Data Types and Memory Objects 161 Chapter 8 Boolean Logic and Digital Design 191 Chapter 9 CPU Architecture 225 Chapter 10 Instruction Set Architecture 259 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info vi Brief Contents Chapter 11 Memory Architecture and Organization 295 Chapter 12 Input and Output (I/O) 329 Thinking Low-Level, Writing High-Level 405 Appendix A ASCII Character Set 407 Index 411 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info CONTENTS IN DETAIL 1 WHAT YOU NEED TO KNOW TO WRITE GREAT CODE 1.1 The Write Great Code Series 1 1.2 What This Volume Covers 3 1.3 Assumptions This Volume Makes 5 1.4 Characteristics of Great Code 6 1.5 The Environment for This Volume 7 1.6 For More Information 7 2 NUMERIC REPRESENTATION 2.1 What Is a Number? 10 2.2 Numbering Systems 11 2.2.1 The Decimal Positional Numbering System 11 2.2.2 Radix (Base) 12 2.2.3 The Binary Numbering System 13 2.2.4 The Hexadecimal Numbering System 15 2.2.5 The Octal (Base-8) Numbering System 18 2.3 Numeric/String Conversions 19 2.4 Internal Numeric Representation 21 2.4.1 Bits 21 2.4.2 Bit Strings 22 2.5 Signed and Unsigned Numbers 24 2.6 Some Useful Properties of Binary Numbers 25 2.7 Sign Extension, Zero Extension, and Contraction 27 2.8 Saturation 30 2.9 Binary-Coded Decimal (BCD) Representation 31 2.10 Fixed-Point Representation 33 2.11 Scaled Numeric Formats 35 2.12 Rational Representation 38 2.13 For More Information 38 3 BINARY ARITHMETIC AND BIT OPERATIONS 3.1 Arithmetic Operations on Binary and Hexadecimal Numbers 39 3.1.1 Adding Binary Values 40 3.1.2 Subtracting Binary Values 41 3.1.3 Multiplying Binary Values 42 3.1.4 Dividing Binary Values 43 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info viii Contents in Detail 3.2 Logical Operations on Bits 46 3.3 Logical Operations on Binary Numbers and Bit Strings 47 3.4 Useful Bit Operations 48 3.4.1 Testing Bits in a Bit String Using AND 48 3.4.2 Testing a Set of Bits for Zero/Not Zero Using AND 49 3.4.3 Comparing a Set of Bits Within a Binary String 49 3.4.4 Creating Modulo-n Counters Using AND 51 3.5 Shifts and Rotates 52 3.6 Bit Fields and Packed Data 55 3.7 Packing and Unpacking Data 60 3.8 For More Information 64 4 FLOATING-POINT REPRESENTATION 4.1 Introduction to Floating-Point Arithmetic 66 4.2 IEEE Floating-Point Formats 71 4.2.1 Single-Precision Floating-Point Format 72 4.2.2 Double-Precision Floating-Point Format 74 4.2.3 Extended-Precision Floating-Point Format 74 4.3 Normalization and Denormalized Values 75 4.4 Rounding 77 4.5 Special Floating-Point Values 78 4.6 Floating-Point Exceptions 79 4.7 Floating-Point Operations 80 4.7.1 Floating-Point Representation 80 4.7.2 Floating-Point Addition and Subtraction 81 4.7.3 Floating-Point Multiplication and Division 92 4.8 For More Information 100 5 CHARACTER REPRESENTATION 5.1 Character Data 104 5.1.1 The ASCII Character Set 104 5.1.2 The EBCDIC Character Set 107 5.1.3 Double-Byte Character Sets 108 5.1.4 The Unicode Character Set 109 5.2 Character Strings 110 5.2.1 Character String Formats 111 5.2.2 Types of Strings: Static, Pseudo-Dynamic, and Dynamic 116 5.2.3 Reference Counting for Strings 117 5.2.4 Delphi/Kylix Strings 118 5.2.5 Creating Your Own String Formats 119 5.3 Character Sets 119 5.3.1 Powerset Representation of Character Sets 120 5.3.2 List Representation of Character Sets 120 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info Contents in Detail ix 5.4 Designing Your Own Character Set 121 5.4.1 Designing an Efficient Character Set 122 5.4.2 Grouping the Character Codes for Numeric Digits 124 5.4.3 Grouping Alphabetic Characters 124 5.4.4 Comparing Alphabetic Characters 126 5.4.5 Other Character Groupings 128 5.5 For More Information 131 6 MEMORY ORGANIZATION AND ACCESS 6.1 The Basic System Components 134 6.1.1 The System Bus 134 6.1.2 The Address Bus 135 6.1.3 The Control Bus 136 6.2 Physical Organization of Memory 137 6.2.1 8-Bit Data Buses 139 6.2.2 16-Bit Data Buses 140 6.2.3 32-Bit Data Buses 142 6.2.4 64-Bit Buses 143 6.2.5 Small Accesses on Non-80x86 Processors 143 6.3 Big Endian Versus Little Endian Organization 144 6.4 The System Clock 149 6.4.1 Memory Access and the System Clock 151 6.4.2 Wait States 152 6.4.3 Cache Memory 153 6.5 CPU Memory Access 157 6.5.1 The Direct Memory Addressing Mode 158 6.5.2 The Indirect Addressing Mode 158 6.5.3 The Indexed Addressing Mode 159 6.5.4 The Scaled Indexed Addressing Modes 160 6.6 For More Information 160 7 COMPOSITE DATA TYPES AND MEMORY OBJECTS 7.1 Pointer Types 162 7.1.1 Pointer Implementation 163 7.1.2 Pointers and Dynamic Memory Allocation 164 7.1.3 Pointer Operations and Pointer Arithmetic 164 7.2 Arrays 169 7.2.1 Array Declarations 169 7.2.2 Array Representation in Memory 172 7.2.3 Accessing Elements of an Array 173 7.2.4 Multidimensional Arrays 174 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info x Contents in Detail 7.3 Records/Structures 181 7.3.1 Records in Pascal/Delphi 181 7.3.2 Records in C/C++ 182 7.3.3 Records in HLA 182 7.3.4 Memory Storage of Records 183 7.4 Discriminant Unions 185 7.4.1 Unions in C/C++ 186 7.4.2 Unions in Pascal/Delphi/Kylix 186 7.4.3 Unions in HLA 187 7.4.4 Memory Storage of Unions 187 7.4.5 Other Uses of Unions 188 7.5 For More Information 189 8 BOOLEAN LOGIC AND DIGITAL DESIGN 8.1 Boolean Algebra 192 8.1.1 The Boolean Operators 192 8.1.2 Boolean Postulates 192 8.1.3 Boolean Operator Precedence 194 8.2 Boolean Functions and Truth Tables 194 8.3 Function Numbers 197 8.4 Algebraic Manipulation of Boolean Expressions 198 8.5 Canonical Forms 199 8.5.1 Sum of Minterms Canonical Form and Truth Tables 200 8.5.2 Deriving the Sum of Minterms Canonical Form Algebraically 202 8.5.3 Product of Maxterms Canonical Form 203 8.6 Simplification of Boolean Functions 204 8.7 What Does This Have to Do with Computers, Anyway? 212 8.7.1 Correspondence Between Electronic Circuits and Boolean Functions 213 8.7.2 Combinatorial Circuits 214 8.7.3 Sequential and Clocked Logic 220 8.8 For More Information 224 9 CPU ARCHITECTURE 9.1 Basic CPU Design 225 9.2 Decoding and Executing Instructions: Random Logic Versus Microcode 228 9.3 Executing Instructions, Step by Step 229 9.3.1 The mov Instruction 230 9.3.2 The add Instruction 232 9.3.3 The jnz Instruction 234 9.3.4 The loop Instruction 234 9.4 Parallelism — The Key to Faster Processing 235 9.4.1 The Prefetch Queue 238 9.4.2 Conditions That Hinder the Performance of the Prefetch Queue 242 9.4.3 Pipelining — Overlapping the Execution of Multiple Instructions 243 9.4.4 Instruction Caches — Providing Multiple Paths to Memory 247 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info [...]... %10 01 $9 %10 10 $A %10 11 $B %11 00 $C %11 01 $D %11 10 $E %11 11 $F To convert the hexadecimal representation of a number into binary, substitute the corresponding four binary bits for each hexadecimal digit For example, to convert $ABCD into the binary form %10 10 _10 11_ 110 0 _11 01, convert each hexadecimal digit according to the values in Table 2 -1: A B C D Hexadecimal 10 10 10 11 110 0 11 01 Binary To convert... 328 12 I NP U T A N D O U T P U T ( I / O ) 12 .1 12.2 12 .3 12 .4 12 .5 12 .6 12 .7 12 .8 12 .9 12 .10 12 .11 12 .12 12 .13 12 .14 12 .15 12 .16 12 .17 12 .18 xii Connecting a CPU to the Outside World 330 Other Ways to Connect Ports to the System 333 I/O Mechanisms 334 12 .3 .1 Memory-Mapped I/O 334 12 .3.2 I/O and the Cache 335 12 .3.3 I/O-Mapped Input/Output 335 12 .3.4... Hierarchy 314 Run-Time Memory Organization 316 11 .9 .1 Static and Dynamic Objects, Binding, and Lifetime 317 11 .9.2 The Code, Read-Only, and Constant Sections 319 11 .9.3 The Static Variables Section 319 11 .9.4 The Uninitialized Storage (BSS) Section 319 11 .9.5 The Stack Section 320 11 .9.6 The Heap Section and Dynamic Memory Allocation 3 21 11. 10 For More Information... corresponding three bits from Table 2-2 For example, when converting 12 3q into a binary value the final result is %0_ 010 1_0 011 : 1 2 3 0 01 010 011 18 C ha pt er 2 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info Table 2-2: Binary/Octal Conversion Chart Binary Octal %000 0 %0 01 1 % 010 2 % 011 3 %10 0 4 %10 1 5 %11 0 6 %11 1 7 To convert a binary number into octal, you break up the binary... easier to read and comprehend than 10 23435208 We’ll adopt a 14 C ha pt er 2 No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info similar convention in this book for binary numbers We will separate each group of four binary bits with an underscore For example, we will write the binary value 10 1 011 111 011 0 010 2 as 10 10 _11 11_ 1 011 _0 010 2 2.2.3.3 Binary Representation in Programming Languages... in code, hexadecimal notation is also popular because it is easy to convert between the binary and hexadecimal representations By memorizing a few simple rules, you can mentally convert between these two representations Consider Table 2 -1 Table 2 -1: Binary/Hexadecimal Conversion Chart Binary Hexadecimal %0000 $0 %00 01 $1 %0 010 $2 %0 011 $3 % 010 0 $4 % 010 1 $5 % 011 0 $6 % 011 1 $7 %10 00 $8 %10 01 $9 %10 10... 293 11 M E M O R Y AR C HI T E C T U R E A ND O R G A N IZ A T I O N 11 .1 11. 2 11 .3 11 .4 The Memory Hierarchy .295 How the Memory Hierarchy Operates 298 Relative Performance of Memory Subsystems 300 Cache Architecture 302 11 .4 .1 Direct-Mapped Cache 303 11 .4.2 Fully Associative Cache 304 11 .4.3 n-Way Set Associative Cache .304 11 .4.4 Matching... by Randall Hyde www.it-ebooks.info 12 .19 12 .20 12 . 21 12.22 12 .23 12 .24 12 .25 12 .26 12 .27 SCSI Devices and Controllers 367 The IDE/ATA Interface .372 File Systems on Mass Storage Devices 374 12 . 21. 1 Maintaining Files Using a Free-Space Bitmap 377 12 . 21. 2 File Allocation Tables 378 12 . 21. 3 List-of-Blocks File Organization 3 81 Writing Software That Manipulates... Data Access .305 11 .4.5 Cache Line Replacement Policies 306 11 .4.6 Writing Data to Memory 307 11 .4.7 Cache Use and Software 308 C ont en t s in D et a il No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info xi 11 .5 11 .6 11 .7 11 .8 11 .9 Virtual Memory, Protection, and Paging 309 Thrashing 312 NUMA and Peripheral Devices 313 Writing Software... given the binary number 10 110 010 10, the first step would be to add two zero bits to the left of the number so that it contains 12 bits without changing its value The result is Num er ic Re pr es en ta t ion No Starch Press, Copyright © 2004 by Randall Hyde www.it-ebooks.info 17 0 010 110 010 10 The next step is to separate the binary value into groups of four bits: 0 010 _11 00 _10 10 Finally, look up these . 347 12 .11 Exploring Specific PC Peripheral Devices 347 12 .12 The Keyboard 348 12 .13 The Standard PC Parallel Port 349 12 .14 Serial Ports 3 51 12 .15 Disk Drives 352 12 .15 .1 Floppy Drives 352 12 .15 .2. REPRESENTATION 5 .1 Character Data 10 4 5 .1. 1 The ASCII Character Set 10 4 5 .1. 2 The EBCDIC Character Set 10 7 5 .1. 3 Double-Byte Character Sets 10 8 5 .1. 4 The Unicode Character Set 10 9 5.2 Character Strings 11 0 5.2 .1. Memory Organization 316 11 .9 .1 Static and Dynamic Objects, Binding, and Lifetime 317 11 .9.2 The Code, Read-Only, and Constant Sections 319 11 .9.3 The Static Variables Section 319 11 .9.4 The Uninitialized