Primer Plus. Fourth Edition. Stephen Prata. 800 East 96th St., Indianapolis, Indiana, USA

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2 C Primer Plus Fourth Edition Stephen Prata 800 East 96th St., Indianapolis, Indiana, USA

3 C Primer Plus, Fourth Edition Copyright 2002 by Sams Publishing All rights reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. No patent liability is assumed with respect to the use of the information contained herein. Although every precaution has been taken in the preparation of this book, the publisher and author assume no responsibility for errors or omissions. Nor is any liability assumed for damages resulting from the use of the information contained herein. International Standard Book Number: Library of Congress Catalog Card Number: Printed in the United States of America First Printing: September Trademarks All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Sams Publishing cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Apple is a registered trademark of Apple Computer, Inc. Borland C++ is a registered trademark of Borland International, Inc. CodeWarrior is a registered trademark of Metrowerks, Inc. Cray is a registered trademark of Cray Computer, Inc. IBM and PC are registered trademarks and PC DOS is a trademark of the International Business Machines Company. Macintosh is a registered trademark of Macintosh Laboratory, Inc., licensed by Apple Computer, Inc. Microsoft and MS-DOS are registered trademarks of Microsoft Corporation. Primer Plus is a registered trademark of The Waite Group, Inc. Think C is a registered trademark of Symantec Corporation. Turbo C is a registered trademark of Borland International, Inc. Unix is a trademark of American Telephone and Telegraph Corporation. VAX is a registered trademark and VMS is a trademark of Digital Equipment Corporation. Windows is a registered trademark of Microsoft Corporation. WordPerfect is a registered trademark of WordPerfect Corporation. WordStar is a registered trademark of MicroPro International Corporation. Warning and Disclaimer Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information provided is on an as is basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the Web site or programs accompanying it. ASSOCIATE PUBLISHER Linda Engelman ACQUISITIONS EDITORS Linda Scharp Karen Wachs DEVELOPMENT EDITOR Karen Wachs MANAGING EDITOR Charlotte Clapp PROJECT EDITOR Sheila Schroeder COPY EDITOR Pat Kinyon INDEXER Sandra Henselmeier PROOFREADER Plan-It Publishing TECHNICAL EDITOR Jeff Perkins Chris Maunder TEAM COORDINATORS Chris Feather Lynne Williams MEDIA DEVELOPER Dan Scherf INTERIOR DESIGNER Gary Adair PAGE LAYOUT Tim Osborn

4 CONTENTS AT A GLANCE PREFACE xx CHAPTER 1 Getting Ready CHAPTER 2 Introducing C CHAPTER 3 Data and C CHAPTER 4 Character Strings and Formatted Input/Output CHAPTER 5 Operators, Expressions and Statements CHAPTER 6 C Control Statements: Looping CHAPTER 7 C Control Statements: Branching and Jumps CHAPTER 8 Character Input/Output and Redirection CHAPTER 9 Functions CHAPTER 10 Arrays and Pointers CHAPTER 11 Character Strings and String Functions CHAPTER 12 Storage Classes, Linkage, and Memory Management CHAPTER 13 File Input/Output CHAPTER 14 Structures and Other Data Forms CHAPTER 15 Bit Fiddling CHAPTER 16 The C Preprocessor and the C Library CHAPTER 17 Advanced Data Representation APPENDIX A Answers to the Review Questions APPENDIX B Reference Section INDEX 871

5 TABLE OF CONTENTS CHAPTER 1: Getting Ready Whence C? Why C? Design Features Efficiency Portability Power and Flexibility Programmer Oriented Shortcomings Whither C? What Computers Do High-Level Computer Languages and Compilers Using C: Seven Steps Step 1: Define the Program Objectives Step 2: Design the Program Step 3: Write the Code Step 4: Compile Step 5: Run the Program Step 6: Test and Debug the Program Step 7: Maintain and Modify the Program Commentary Programming Mechanics Object Code Files, Executable Files, and Libraries UNIX System Linux System Integrated Development Environments (Windows) DOS Compilers for the IBM PC C on the Macintosh Language Standards The First ANSI/ISO C Standard The C99 Standard Book Organization Some Conventions Typeface Screen Output Summary Review Questions Programming Exercise

6 CONTENTS v CHAPTER 2: Introducing C A Simple Sample of C The Explanation Pass 1 Quick Synopsis Pass 2 Details The Structure of a Simple Program Tips on Making Your Programs Readable Taking Another Step Documentation Multiple Declarations Multiplication Printing Multiple Values While You re at It Multiple Functions Debugging Syntax Errors Semantic Errors Program State Keywords and Reserved Identifiers Key Concepts Summary Review Questions Programming Exercises CHAPTER 3: Data and C A Sample Program What s New in This Program? Data Variables and Constants Data: Data-Type Keywords Integer Versus Floating-Point Types The Integer The Floating-Point Number C Data Types The int Type Other Integer Types Using Characters: Type char The _Bool Type Portable Types: inttypes.h Types float, double, and long double Complex and Imaginary Types Other Types Type Sizes

7 vi C PRIMER PLUS Using Data Types Arguments and Pitfalls One More Example What Happens Flushing the Output Key Concepts Summary Review Questions Programming Exercises CHAPTER 4: Character Strings and Formatted Input/Output Introductory Program Character Strings: An Introduction Type char Arrays and the Null Character Using Strings The strlen() Function Constants and the C Preprocessor The const Modifier Manifest Constants on the Job Exploring and Exploiting printf() and scanf() The printf() Function Using printf() Conversion Specification Modifiers for printf() The Meaning of Conversion Using scanf() The * Modifier with printf() and scanf() Usage Tips Key Concepts Summary Review Questions Programming Exercises CHAPTER 5: Operators, Expressions, and Statements Introducing Loops Fundamental Operators Assignment Operator: = Addition Operator: Subtraction Operator: Sign Operators: and Multiplication Operator: * Division Operator: / Operator Precedence Precedence and the Order of Evaluation

8 CONTENTS vii Some Additional Operators The sizeof Operator and the size_t Type Modulus Operator: % Increment and Decrement Operators: ++ and Decrementing: Precedence Don t Be Too Clever Expressions and Statements Expressions Statements Compound Statements (Blocks) Type Conversions The Cast Operator Function with Arguments A Sample Program Key Concepts Summary Review Questions Programming Exercises CHAPTER 6: C Control Statements: Looping An Initial Example Program Comments C-Style Reading Loop The while Statement Terminating a while Loop When a Loop Terminates while: An Entry-Condition Loop Syntax Points Which Is Bigger: Using Relational Operators and Expressions What Is Truth? What Else Is True? Troubles with Truth The New _Bool Type Precedence of Relational Operators Indefinite Loops and Counting Loops The for Loop Using for for Flexibility More Assignment Operators: +=, -=, *=, /=, %= The Comma Operator Zeno Meets the for Loop

9 viii C PRIMER PLUS An Exit-Condition Loop: do while Which Loop? Nested Loops Program Discussion A Nested Variation Arrays Using a for Loop with an Array A Loop Example Using a Function Return Value Program Discussion Using Functions with Return Values Key Concepts Summary Review Questions Programming Exercises CHAPTER 7: C Control Statements: Branching and Jumps The if Statement Adding else to the if Statement Another Example: Introducing getchar() and putchar() The ctype.h Family of Character Functions Multiple Choice else if Pairing else with if More Nested ifs Let s Get Logical Alternate Spellings: the iso646.h header file Precedence Order of Evaluation Ranges A Word-Count Program The Conditional Operator:? Loop Aids: continue and break The continue Statement The break Statement Multiple Choice: switch and break Using the switch Statement Reading Only the First Character of a Line Multiple Labels switch and if else The goto Statement Avoiding goto

10 CONTENTS ix Key Concepts Summary Review Questions Programming Exercises CHAPTER 8: Character Input/Output and Input Validation Single-Character I/O: getchar() and putchar() Buffers Terminating Keyboard Input Files, Streams, and Keyboard Input The End of File Redirection and Files Unix, Linux, and DOS Redirection Creating a Friendlier User Interface Working with Buffered Input Mixing Numeric and Character Input Input Validation Analyzing the Program The Input Stream and Numbers Menu Browsing Tasks Toward a Smoother Execution Mixing Character and Numeric Input Key Concepts Summary Review Questions Programming Exercises CHAPTER 9: Functions Reviewing Functions Creating and Using a Simple Function Analyzing the Program Function Arguments Defining a Function with an Argument: Formal Parameters Prototyping a Function with Arguments Calling a Function with an Argument: Actual Arguments The Black Box Viewpoint Returning a Value from a Function with return Function Types ANSI C Function Prototyping The Problem The ANSI Solution

11 x C PRIMER PLUS No Arguments and Unspecified Arguments Hooray for Prototypes Recursion Recursion Revealed Recursion Fundamentals Tail Recursion Recursion and Reversal Recursion Pros and Cons All C Functions Are Created Equal Compiling Programs with Two or More Source Code Files UNIX Linux DOS Command-Line Compilers Windows and Macintosh Compilers Using Header Files Finding Addresses: The & Operator Altering Variables in the Calling Function Pointers: A First Look The Indirection Operator: * Declaring Pointers Using Pointers to Communicate Between Functions Key Concepts Summary Review Questions Programming Exercises CHAPTER 10: Arrays and Pointers Arrays Initialization Designated Initializers (C99) Assigning Array Values Array Bounds Specifying an Array Size Multidimensional Arrays Initializing a Two-Dimensional Array More Dimensions Pointers and Arrays Functions, Arrays, and Pointers Using Pointer Arguments Comment: Pointers and Arrays Pointer Operations

12 CONTENTS xi Protecting Array Contents Using const with Formal Parameters More About const Pointers and Multidimensional Arrays Pointers to Multi-Dimensional Arrays Pointer Compatibility Functions and Multidimensional Arrays Variable-Length Arrays (VLAs) Compound Literals Key Concepts Summary Review Questions Programming Exercises CHAPTER 11: Character Strings and String Functions Defining Strings Within a Program Character String Constants (String Literals) Character String Arrays and Initialization Array Versus Pointer Arrays of Character Strings Pointers and Strings String Input Creating Space The gets() Function The fgets() Function The scanf() Function String Output The puts() Function The fputs() Function The printf() Function The Do-It-Yourself Option String Functions The strlen() Function The strcat() and strncat() Functions The strcmp() and strncmp() Functions The strcpy() and strncpy() Functions The sprintf() Function Other String Functions A String Example: Sorting Strings Sorting The ctype.h Character Functions and Strings

13 xii C PRIMER PLUS Command-Line Arguments Command-Line Arguments in Integrated Environments Command-Line Arguments with the Macintosh String to Number Conversions Key Concepts Summary Review Questions Programming Exercises CHAPTER 12: Storage Classes, Linkage, and Memory Management Storage Classes Scope Linkage Storage Duration Automatic Variables Register Variables Static Variables with Block Scope Static Variables with External Linkage Static Variables with Internal Linkage Multiple Files Storage-Class Specifiers Storage Classes and Functions Which Storage Class? A Random Number Function and a Static Variable Roll Em Allocated Memory: malloc() and free() The Importance of free() The calloc() Function Dynamic Memory Allocation and Variable-Length Arrays Storage Classes and Dynamic Memory Allocation ANSI C Type Qualifiers The const Type Qualifier The volatile Type Qualifier The restrict Type Qualifier New Places for Old Keywords Key Concepts Summary Review Questions Programming Exercises

14 CONTENTS xiii CHAPTER 13: File Input/Output Communicating with Files What Is a File? Levels of I/O Standard Files Standard I/O Checking for Command-Line Arguments The fopen() Function The getc() and putc() Functions End of File The fclose() Function Standard Files A Simple-Minded File-Condensing Program File I/O: fprintf(), fscanf(), fgets(), and fputs() The fprintf() and fscanf() Functions The fgets() and fputs() Functions Adventures in Random Access: fseek() and ftell() How fseek() and ftell() Work Binary Versus Text Mode Portability The fgetpos() and fsetpos() Functions Behind the Scenes with Standard I/O Other Standard I/O Functions The int ungetc(int c, FILE *fp) Function The int fflush(file *fp) Function The int setvbuf(file *fp, char *buf, int mode, size_t size) Function Binary I/O: fread() and fwrite() The size_t fwrite(void *ptr, size_t size, size_t nmemb, FILE *fp) Function The size_t fread(void *ptr, size_t size, size_t nmemb, FILE *fp) Function The int feof(file *fp) and int ferror(file *fp) Functions An Example Random Access with Binary I/O Key Concepts Summary Review Questions Programming Exercises CHAPTER 14: Structures and Other Data Forms Sample Problem: Creating an Inventory of Books Setting Up the Structure Declaration

15 xiv C PRIMER PLUS Defining a Structure Variable Initializing a Structure Designated Initializers for Structures Gaining Access to Structure Members Arrays of Structures Declaring an Array of Structures Identifying Members of an Array of Structures Program Discussion Nested Structures Pointers to Structures Declaring and Initializing a Structure Pointer Member Access by Pointer Telling Functions About Structures Passing Structure Members Using the Structure Address Passing a Structure as an Argument More on Structure Features Structures or Pointer to Structures? Character Arrays or Character Pointers in a Structure Structure, Pointers, and malloc() Compound Literals and Structures (C99) Flexible Array Members (C99) Functions Using an Array of Structures Saving the Structure Contents in a File Program Points Structures: What Next? Unions: A Quick Look Enumerated Types enum Constants Default Values Assigned Values Usage Shared Namespaces typedef: A Quick Look Fancy Declarations Functions and Pointers Key Concepts Summary Review Questions Programming Exercises

16 CONTENTS xv CHAPTER 15: Bit Fiddling Binary Numbers, Bits, and Bytes Binary Integers Signed Integers Binary Floating Point Other Bases Octal Hexadecimal C s Bitwise Operators Bitwise Logical Operators Usage: Masks Usage: Turning Bits On Usage: Turning Bits Off Usage: Toggling Bits Usage: Checking the Value of a Bit Bitwise Shift Operators Programming Example Another Example Bit Fields Bit-Field Example Bit Fields and Bitwise Operators Key Concepts Summary Review Questions Programming Exercises CHAPTER 16: The C Preprocessor and the C Library First Steps Manifest Constants: #define Tokens Redefining Constants Using Arguments with #define Creating Strings from Macro Arguments: The # Operator Preprocessor Glue: the ## Operator Variadic Macros:... and VA_ARGS Macro or Function? File Inclusion: #include Header Files: An Example Uses for Header Files

17 xvi C PRIMER PLUS Other Directives The #undef Directive Being Defined the C Preprocessor Perspective Conditional Compilation Predefined Macros #line and #error #pragma Inline Functions The C Library Gaining Access to the C Library Using the Library Descriptions The Math Library The General Utilities Library The exit() and atexit() Functions The qsort() Function The Assert Library memcpy() and memmove() from the string.h Library Variable Arguments: stdarg.h Key Concepts Summary Review Questions Programming Exercises CHAPTER 17: Advanced Data Representation Exploring Data Representation Beyond the Array to the Linked List Using a Linked List Afterthoughts Abstract Data Types (ADTs) Getting Abstract Building an Interface Using the Interface Implementing the Interface Getting Queued with an ADT Implementing the Interface Data Representation Testing the Queue Simulating with a Queue The Linked List Versus the Array Binary Search Trees A Binary Tree ADT The Binary Search Tree Interface The Binary Tree Implementation

18 CONTENTS xvii Trying the Tree Tree Thoughts Other Directions Key Concepts Summary Review Questions Programming Exercises APPENDIX A: Answers to the Review Questions hapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter Chapter APPENDIX B: Reference Section Section I Additional Reading Magazine Online Resources C Language Books Programming Reference C++ Books Section II C Operators Arithmetic Operators Relational Operators Assignment Operators Logical Operators The Conditional Operator Pointer-Related Operators

19 xviii C PRIMER PLUS Sign Operators Structure and Union Operators Bitwise Operators Miscellaneous Operators Section III Basic Types and Storage Classes Summary: The Basic Data Types Summary: How to Declare a Simple Variable Summary: Qualifiers Section IV Expressions, Statements, and Program Flow Summary: Expressions and Statements Summary: The while Statement Summary: The for Statement Summary: The do while Statement Summary: Using if Statements for Making Choices Summary: Multiple Choice with switch Summary: Program Jumps Section V The Standard ANSI C Library with C99 Additions Diagnostics: assert.h Complex Numbers: complex.h (C99) Character Handling: ctype.h Error Reporting: errno.h Floating-Point Environment: fenv.h (C99) Format Conversion of Integer Types: inttypes.h (C99) Localization: locale.h Math Library: math.h Non-Local Jumps: setjmp.h Signal Handling: signal.h Variable Arguments: stdarg.h Boolean Support: stdbool.h (C99) Common Definitions: stddef.h Integer Types: stdint.h Standard I/O Library: stdio.h General Utilities: stdlib.h String Handling: string.h Type-Generic Math: tgmath.h (C99) Date and Time: time.h Extended Multibyte and Wide Character Utilities: wchar.h (C99) Wide Character Classification and Mapping Utilities: wctype.h (C99) Section VI Extended Integer Types Exact Width Types Minimum Width Types

20 CONTENTS xix Fastest Minimum Width Types Maximum Width Types Integers That Can Hold Pointer Values Extended Integer Constants Section VII Expanded Character Support Trigraph Sequences Digraphs Alternative Spellings: iso646.h Multibyte Characters Universal Character Names (UCNs) Wide Characters Wide Characters and Multibyte Characters Section VIII C99 Numeric Computational Enhancements The IEC Floating-Point Standard The fenv.h Header File The STDC FP_CONTRACT Pragma Additions to the math.h Library Support for Complex Numbers Section IX Differences Between C and C Function Prototypes char Constants The const Modifier Structures and Unions Enumerations Pointer to void Boolean Types Alternative Spellings Wide Character Support Complex Types Inline Functions C++ Doesn t Have It INDEX

21 PREFACE C was a relatively little-known language when the first edition of C Primer Plus was written in Since then, the language has boomed, and many people have learned C with the help of this book. In fact, over 500,000 people have purchased C Primer Plus throughout its various editions. With the emergence of a new standard for C, it s time for a 4 th edition. As with all the editions, my aim has been to create an introduction to C that is instructive, clear, and helpful. Approach and Goals My goal is for this book to serve as a friendly, easy-to-use, self-study guide. To accomplish that objective, C Primer Plus employs the following strategies: Programming concepts are explained, along with details of the C language; the book does not assume that you are a professional programmer. Many short, easily-typed examples illustrate just one or two concepts at a time, because learning by doing is one of the most effective ways to master new information. Figures and illustrations clarify concepts that are difficult to grasp in words alone. Highlight boxes summarize the main features of C for easy reference and review. Review questions and programming exercises at the end of each chapter allow you to test and improve your understanding of C. To gain the greatest benefit, you should take as active a role as possible in studying the topics in this book. Don t just read the examples, enter them into your system and try them. C is a very portable language, but you may find differences between how a program works on your system and how it works on ours. Experiment change part of a program to see what the effect is. Modify a program to do something slightly different. Ignore the occasional warnings and see what happens when you do the wrong thing. Try the questions and exercises. The more you do yourself, the more you will learn and remember. I hope that you ll find this newest edition an enjoyable and effective introduction to the C language. Changes in the 4 th Edition There is a new standard for the C language. It s called the ISO/IEC 9899:1999 International Standard, but among friends it often goes by the simpler name of C99. It was adopted by the International Organization for Standardization (ISO) and the International Electrotechnical

22 Committee (IEC) in 1999 and approved as the American standard by the American National Standards Institute (ANSI) in This new edition of C Primer Plus incorporates the new standard. Here are some of the new features covered: Extended integer types Expanded character support Boolean support Variable-length arrays Compound literals Designated initializers Expanded computational support Inline functions This edition also reorganizes the presentation of some topics. For example, the discussion of pointers in Chapter 10, Arrays and Pointers, has been consolidated and expanded, and Chapter 12, Storage Classes, Linkage, and Memory Management, incorporates dynamic memory allocation into the discussion of C storage classes and memory management. Numerous other changes and additions have been incorporated in response to reader requests to make this edition an even more effective learning tool.

23 ABOUT THE AUTHOR Stephen Prata is a professor of physics and astronomy at the College of Marin in Kentfield, California, where he teaches astronomy, physics, and programming. He received his B.S. from the California Institute of Technology and his Ph.D. from the University of California, Berkeley. His association with computers began with the computer modeling of star clusters. Stephen has authored or coauthored over a dozen books, including C++ Primer Plus and Unix Primer Plus.

24 DEDICATION With love to Vicky and Bill Prata, who, for more than 65 years, have been showing how rewarding a marriage can be. SP

The Waite Group's. New. Primer Plus. Second Edition. Mitchell Waite and Stephen Prata SAMS

The Waite Group's. New. Primer Plus. Second Edition. Mitchell Waite and Stephen Prata SAMS The Waite Group's New Primer Plus Second Edition Mitchell Waite and Stephen Prata SAMS PUBLISHING A Division of Prentice Hall Computer Publishing 11711 North College, Carmel, Indiana 46032 USA Contents