When a program is compiled, the time-consuming task of translating the source code into machinelanguage has already been accomplished.. The word program is used in two ways: to describe
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What’s New with This Edition
Teach Yourself ANSI C++ in 21 Days, Premier Edition, is a new edition of the international bestseller, Teach Yourself C++ in 21 Days This Premier Edition offers
more than just 21 days of learning ANSI/ISO C++
Major changes throughout this edition have been made to reflect the latest ANSI/ISO C++ draft standard In addition, seven new lessons, referred to as “Bonus Days,”have been added to provide you with additional information for creating moresophisticated programs The Bonus Day lessons are not required reading in orderfor you to learn to program in C++ As a matter of fact, on the very first day you willwrite a simple C++ program
On Bonus Day 22, “Advanced C++ Features,” you learn to use a collection ofspecialized ANSI C++ tools that many programmers don’t even realize exist Thesetools are not essential for every C++ programmer to know but are indispensable inmany circumstances
Bonus Day 23, “More About Streams,” covers some of the more advanced streamsprogramming techniques After completing this lesson, you will have all you need
to create new manipulators for the stream classes you learn to create on Day 16 Youwill also learn a great deal about other streams programming techniques that spacewould not allow us to cover on Day 16
On Bonus Day 24, “Object-Oriented Design,” you learn more about this importantsubject Without object-oriented design techniques, C++ is “just another C” withfew advantages over its predecessor This lesson helps you think in a way that builds
on the object-oriented design paradigm
Bonus Days 25 and 26, “Data Structures” and “Simple Sorting and SearchingAlgorithms,” respectively, introduce you to the inner sanctum of computer science
On these two days you learn how to solve several common categories of problems
“Common Mistakes and Basic Debugging,” on Bonus Day 27, is designed to helpyou avoid some of the common mistakes that many beginning programmers make.Not all errors can be avoided, but with this lesson you should more quickly recognizemany errors by their categories and more quickly find their solutions
The final day of the bonus week, “What’s Next?,” gives you some insight on where
to turn when you run into a question that this book doesn’t seem to answer It alsoprovides the resources you need to further improve your C++ programming skills
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teach yourself
ANSI C++
in 21 days, Premier Edition
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Technical Reviewer
Justin Bell John W Charlesworth
SA Springer, Tim Taylor, Andrew Stone, Mark Walchle Todd Wente, Colleen Williams
Copyright 1996 by Sams Publishing
PREMIER EDITION
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
responsi-bility for errors or omissions Neither is any liaresponsi-bility assumed for damages
resulting from the use of the information contained herein For
informa-tion, address Sams Publishing, 201 W 103rd St., Indianapolis, IN 46290.
International Standard Book Number: 0-672-30887-6
Library of Congress Catalog Card Number: 95-72920
99 98 97 96 4 3 2 1
Interpretation of the printing code: the rightmost double-digit number is
the year of the book’s printing; the rightmost single-digit, the number of the
book’s printing For example, a printing code of 96-1 shows that the first
printing of the book occurred in 1996.
Composed in Agaramond and MCPdigital by Macmillan Computer Publishing
Printed in the United States of America
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.
Publisher and President Richard K Swadley
Acquisitions Manager Greg Wiegand
Managing Editor Cindy Morrow
Marketing Manager Gregg Bushyeager
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Overview
21 Working with Multiple Files for Large Programs 609
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Bonus Days At A Glance 635
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Contents
A Note to C Programmers 2
Where You Are Going 2
Day 1 Getting Started 3 A Brief History of C++ 3
ANSI/ISO C++ 5
What Is a Program? 5
Sophisticated Tools for Sophisticated Programming 6
Procedural, Structured, and Object-Oriented Programming 6
C++ and Object-Oriented Programming 8
How C++ Evolved 9
Should I Learn C First? 10
Preparing to Program 10
Your Development Environment 11
Compiling the Source Code 12
Creating an Executable File with the Linker 12
The Development Cycle 13
HELLO.CPP: Your First C++ Program 14
Compile Errors 15
Summary 16
Q&A 16
Quiz 17
Exercises 17
2 The Parts of a C++ Program 19 The Parts of a Simple Program 19
A Brief Look at cout 21
Comments 22
Types of Comments 23
Using Comments 23
Comments at the Top of Each File 24
A Final Word of Caution About Comments 25
Functions 26
Using Functions 27
Summary 29
Q&A 29
Quiz 29
Exercises 30
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3 Variables and Constants 31
What Is a Variable? 31
Setting Aside Memory 32
Size of Integers 33
Signed and Unsigned 34
Fundamental Variable Types 35
Defining a Variable 36
Case Sensitivity 37
Keywords 38
Creating More Than One Variable at a Time 39
Assigning Values to Your Variables 39
typedef 40
Choosing Between short and long 41
Wrapping Around in Unsigned Integers 42
Wrapping Around a Signed Integer 43
Characters 43
chars and Numbers 44
Special Printing Characters 44
Constants 46
Literal Constants 46
Symbolic Constants 46
Enumerated Constants 49
Summary 50
Q&A 51
Quiz 52
Exercises 53
4 Expressions and Statements 55 Statements 56
Whitespace 56
Blocks and Compound Statements 57
Expressions 57
Operators 59
Assignment Operator 59
Mathematical Operators 60
Integer Division and Modulus 60
Combining the Assignment and Mathematical Operators 61
Increment and Decrement 62
Prefix and Postfix 62
Precedence 64
Nesting Parentheses 64
The Bitwise Operators 65
Operator AND 66
Operator OR 67
Operator Exclusive OR 67
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The Complement Operator 67
Shift Operators 67
Setting Bits 67
Clearing Bits 68
Flipping Bits 68
Fast Math Through the Power of the Bit 68
The Nature of Truth 69
Relational Operators 69
The if Statement 70
else 73
Advanced if Statements 75
Using Braces in Nested if Statements 76
Logical Operators 79
Logical AND 79
Logical OR 80
Logical NOT 80
Relational Precedence 80
More About Truth and Falsehood 81
Conditional (Ternary) Operator 82
Summary 84
Q&A 84
Quiz 85
Exercises 85
5 Functions 87 What Is a Function? 88
Declaring and Defining Functions 88
Declaring the Function 89
Function Prototypes 89
Defining the Function 91
Execution of Functions 93
Local Variables 93
Global Variables 95
More on Local Variables 97
Function Statements 99
Function Arguments 99
Using Functions as Parameters to Functions 99
Parameters Are Local Variables 100
Return Values 101
Default Parameters 103
Overloading Functions 106
Special Topics 108
Inline Functions 109
Recursion 111
Summary 114
Q&A 114
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Quiz 115
Exercises 115
Extra Credit 116
How Functions Work 117
Levels of Abstraction 117
Partitioning RAM 117
The Stack and Functions 120
6 Basic Classes 123 Creating New Types 124
Why Create a New Type? 124
Classes and Members 124
Declaring a Class 125
Classes Versus Objects 126
Defining an Object 126
Accessing Class Members 126
Assign to Objects, Not to Classes 126
If It’s Not Declared, Your Class Won’t Have It 127
Private Versus Public 128
Make Member Data Private 130
Privacy Versus Security 132
Implementing Class Methods 134
Constructors and Destructors 136
Default Constructors and Destructors 137
const Member Functions 140
Interface Versus Implementation 141
Where to Put Class Declarations and Method Definitions 143
Inline Implementation 145
Classes with Other Classes as Member Data 147
Structures 150
Why Two Keywords Do the Same Thing 151
Summary 152
Q&A 152
Quiz 153
Exercises 154
7 More Program Flow 155 Looping 156
The Roots of Looping goto 156
Why goto Is Shunned 157
while Loops 157
More Complicated while Statements 159
continue and break 160
The while (true) Loop 163
do…while Loops 164
The do…while Loop 165
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for Loops 167
Advanced for Loops 169
Empty for Loops 172
Nested Loops 173
Scoping in Loops 174
Summing Up Loops 174
switch Statements 177
Using a switch Statement with a Menu 180
Summary 183
Q&A 183
Quiz 184
Exercises 184
Week 1 In Review 187 Week In Review 192
Week 2 At A Glance 193 Where You Are Going 193
Day 8 Pointers 195 What Is a Pointer? 195
Storing the Address in a Pointer 197
The Indirection Operator 199
Pointers, Addresses, and Variables 200
Manipulating Data by Using Pointers 201
Examining the Address 202
Why Would You Use Pointers? 204
The Stack and the Free Store 204
new 206
delete 206
Memory Leaks 208
Creating Objects on the Free Store 209
Deleting Objects 210
Accessing Data Members 211
Member Data on the Free Store 212
The this Pointer 213
Stray or Dangling Pointers 215
const Pointers 218
const Pointers and const Member Functions 218
const this Pointers 220
Summary 220
Q&A 221
Quiz 221
Exercises 221
9 References 223 What Is a Reference? 223
Requesting the Address of a Reference 225
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What Can Be Referenced? 228
Null Pointers and Null References 230
Passing Function Arguments by Reference 230
Making swap() Work with Pointers 231
Implementing swap() with References 233
Understanding Function Headers and Prototypes 234
Returning Multiple Values 235
Returning Values by Reference 237
Passing by Reference for Efficiency 238
Passing a const Pointer 241
References as an Alternative 243
Choosing Between References and Pointers 245
Pointer References 246
Mixing References and Pointers 248
Don’t Return a Reference to an Object that Isn’t in Scope! 249
Returning a Reference to an Object on the Heap 251
Who Has the Pointer? 253
Summary 253
Q&A 254
Quiz 254
Exercises 254
10 Advanced Functions 257 Overloaded Member Functions 257
Using Default Values 260
Choosing Between Default Values and Overloaded Functions 262
The Default Constructor 262
Overloading Constructors 263
Initializing Objects 264
The Copy Constructor 265
Operator Overloading 270
Writing an Increment Function 271
Overloading the Prefix Operator 272
Returning Types in Overloaded Operator Functions 273
Returning Nameless Temporaries 274
Using the this Pointer 276
Overloading the Postfix Operator 277
operator+ 279
Overloading operator+ 281
Issues in Operator Overloading 282
Limitations on Operator Overloading 283
What to Overload 283
operator= 284
Conversion Operators 286
Operator unsigned short() 288
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Summary 289
Q&A 290
Quiz 291
Exercises 291
11 Arrays 293 What Is an Array? 293
Array Elements 294
Writing Past the End of an Array 295
Fence Post Errors 298
Initializing Arrays 298
Declaring Arrays 299
Arrays of Objects 301
Multidimensional Arrays 302
Initializing Multidimensional Arrays 303
A Word About Memory 304
Arrays of Pointers 305
Declaring Arrays on the Free Store 306
A Pointer to an Array Versus an Array of Pointers 307
Pointers and Array Names 307
Deleting Arrays on the Free Store 309
char Arrays 310
strcpy() and strncpy() 312
String Classes 313
Linked Lists and Other Structures 320
Array Classes 325
Summary 326
Q&A 327
Quiz 327
Exercises 328
12 Inheritance 329 What Is Inheritance? 329
Inheritance and Derivation 330
The Animal Kingdom 331
The Syntax of Derivation 331
Private Versus Protected Class Members 333
Constructors and Destructors 335
Passing Arguments to Base Constructors 337
Overriding Functions 341
Hiding the Base Class Method 343
Calling the Base Method 345
Virtual Methods 346
You Can’t Get There from Here 351
Slicing 351
Virtual Destructors 353
Virtual Copy Constructors 354
The Cost of Virtual Methods 357
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Summary 357
Q&A 358
Quiz 359
Exercises 359
13 Multiple Inheritance 361 Problems with Single Inheritance 361
Percolating Upward 365
The Parts of a Multiple Inheritance Object 368
Constructors in Multiple Inheritance Objects 369
Ambiguity Resolution 371
Inheriting from a Shared Base Class 372
Virtual Inheritance 376
Problems with Multiple Inheritance 379
Mixins and Capabilities Classes 380
Abstract Data Types 381
Pure Virtual Functions 384
Implementing Pure Virtual Functions 385
Complex Hierarchies of Abstraction 389
Which Types Are Abstract? 392
Summary 393
Q&A 393
Quiz 394
Exercises 394
14 Special Classes and Functions 395 Static Member Data 395
Static Member Functions 400
Pointers to Functions 402
Why Use Function Pointers? 406
Arrays of Pointers to Functions 408
Passing Pointers to Functions to Other Functions 410
Using typedef with Pointers to Functions 412
Pointers to Member Functions 413
Arrays of Pointers to Member Functions 415
Summary 417
Q&A 418
Quiz 418
Exercises 419
Week 2 In Review 421 Week 3 At A Glance 431 Where You Are Going 431
Day 15 Advanced Inheritance 433 Containment 433
Accessing Members of the Contained Class 439
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Filtering Access to Contained Members 439
Cost of Containment 440
Copying by Value 442
Delegation Versus Implemented in Terms of 443
Delegation 444
Private Inheritance 449
Friend Classes 453
friend Functions 460
friend Functions and Operator Overloading 460
Overloading the Insertion Operator 463
Summary 465
Q&A 465
Quiz 466
Exercises 466
16 Streams 469 Overview of Streams 469
Encapsulation 470
Buffering 471
Streams and Buffers 473
Standard I/O Objects 474
Redirection 474
Input Using cin 475
Strings 476
String Problems 477
operator>> Returns a Reference to an istream Object 479
Other Member Functions of cin 480
Single Character Input 480
Getting Strings from Standard Input 482
Using cin.ignore() 485
peek() and putback() 486
Output with cout 487
Flushing the Output 487
Related Functions 488
Manipulators, Flags, and Formatting Instructions 489
Using cout.width() 490
Setting the Fill Characters 491
Set Flags 491
Streams Versus the printf() Function 493
File Input and Output 495
ofstream 495
Condition States 496
Opening Files for Input and Output 496
Changing the Default Behavior of ofstream on Open 498
Binary Versus Text Files 500
Command-Line Processing 502
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Summary 505
Q&A 506
Quiz 506
Exercises 507
17 The Preprocessor 509 The Preprocessor and the Compiler 509
Seeing the Intermediate Form 510
Using #define 510
Using #define for Constants 510
Using #define for Tests 511
The #else Precompiler Command 511
The #error Directive 512
The #pragma Directive 513
Inclusion and Inclusion Guards 513
Defining on the Command Line 514
Undefining 514
Conditional Compilation 516
Macro Functions 516
Why All the Parentheses? 517
Macros Versus Functions and Templates 519
Inline Functions 519
String Manipulation 521
Stringizing 521
Concatenation 521
Predefined Macros 522
assert() 522
Debugging with assert() 524
assert() Versus Exceptions 524
Side Effects 525
Class Invariants 525
Printing Interim Values 529
Debugging Levels 531
Summary 534
Q&A 535
Quiz 535
Exercises 536
18 Creating Reusable Code 537 Remember Code Reuse 538
Avoid Literal Constants 538
Encapsulate the Details 539
Comment on the Logic 539
Remember Code Maintenance 541
The Power of Seven 541
Document the Initial Code and Changes 541
Develop a Consistent Coding Style 542
Develop a Maintenance Strategy 545
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Remember Code Portability 546
Adhere to the ANSI/ISO Standard 547
Think Globally 548
Summary 549
Q&A 549
Quiz 550
Exercises 550
19 Templates 551 What are Templates? 551
Parameterized Types 552
Template Definition 552
Using the Name 554
Implementing the Template 554
Template Functions 558
Templates and Friends 558
Nontemplate Friend Classes and Functions 559
General Template Friend Class or Function 561
A Type-Specific Template Friend Class or Function 563
Using Template Items 564
Specialized Functions 567
Static Members and Templates 573
The Standard Template Library 575
Summary 576
Q&A 577
Quiz 578
Exercises 578
20 Exceptions and Error Handling 581 Bugs, Errors, Mistakes, and Code Rot 582
Exceptions 583
A Word About Code Rot 583
Preparing for Exceptions With C++ 584
How Exceptions Are Used 584
Using try Blocks and catch Blocks 589
Catching Exceptions 590
More Than One catch Specification 590
Exception Hierarchies 593
Data in Exceptions and Naming Exception Objects 594
Exceptions and Templates 600
Exceptions Without Errors 603
Bugs and Debugging 603
Breakpoints 604
Watch Points 604
Examining Memory 604
Assembler 605
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Summary 605
Q&A 605
Quiz 606
Exercises 607
21 Working With Multiple Files for Large Programs 609 Basic Concepts 610
Header Files 610
Precompiled Header Files 612
Variable Names and Function Prototypes 613
Implementation Files and Variable Scope 613
Interdependency of Variables Between Files 615
More About extern 618
Hiding Variables and Global Scope Resolution 618
Avoiding Multiple Declarations 620
Summary 621
Q&A 621
Quiz 622
Exercises 622
Week 3 In Review 625 Bonus Week At A Glance 635 Day 22 Advanced C++ Features 637 Namespaces and Class Libraries 638
Namespaces 638
Class Library Design 640
How Polymorphism Works 643
Casting and Run-Time Type Identification 644
Const Cast 645
Dynamic Cast 646
Static Cast 649
Reinterpret Cast 650
Type Info 651
Explicit Constructors 651
Data Alignment and Assembly Language 652
Packing Data by Understanding Data Alignment 653
Spiking with Assembly Language 653
Summary 654
Q&A 655
Quiz 655
Exercises 656
23 More About Streams 659 The Streams Hierarchy 659
Using istrstream 660
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Using ostrstream 662
Stream Position 663
Format Specification Flags 664
Creating Manipulators and Custom Stream Operators 664
Multiple Streams 667
Summary 671
Q&A 671
Quiz 672
Exercises 672
24 Object-Oriented Design 673 What OOD Is Not 673
Structured Programming 674
Structured Programming Drawbacks 674
OOD Steps 675
Identify the Objects 675
Identify the Methods 676
Establish the Visibility 677
Establish the Interface 677
Implement the Objects 678
Maintain or Iterate the Design 678
Other OOD Descriptions 679
When Not to Use OOD 679
Summary 680
Q&A 681
Quiz 681
Exercises 681
25 Data Structures 683 Looking Back at Arrays 683
Queues and Stacks 684
A Simple Queue Example 684
A Simple Stack Example 688
Trees 689
Summary 698
Q&A 698
Quiz 699
Exercises 699
26 Simple Sorting and Searching 701 Sorting 702
The Bubble Sort 703
The Selection Sort 706
The Shell Sort 707
The Quick Sort 710
Sorting Disk Files 712
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Searching 712The Straightforward String Search 712The Binary Search 714Summary 717Q&A 717Quiz 718Exercises 718
27 Common Mistakes and Basic Debugging 721
Class Explosion 721Boundary Violations and Off-by-One Errors 725Increment and Decrement Errors 726Pointer Problems 726Bracket or Parenthesis Mismatch 727Test and Assignment Confusion 728Debugging Tips 728Asking for Help 729Summary 729Q&A 730Quiz 730Exercises 731
28 What’s Next? 733
The Standard Libraries 734String 735Localization Library 735Containers, Iterators, and Algorithms 735Bit Fields and Bitset 736Numerics Library 737Next Steps 737Sharpening Your Skills 737Other Great Books 737Magazines 738Internet and the World Wide Web 738Electronic Mail 739Summary 739Q&A 739Quiz 740
Appendixes
A Operator Precedence 741
B C++ Keywords 745
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C Binary and Hexadecimal 747
Other Bases 748Around the Bases 749Binary 750Why Base 2? 751Bits, Bytes, and Nibbles 751Binary Numbers 752Hexadecimal 752
D Answers 757
Day 1 758Quiz 758Exercises 758Day 2 758Quiz 758Exercises 759Day 3 760Quiz 760Exercises 761Day 4 761Quiz 761Exercises 762Day 5 764Quiz 764Exercises 765Day 6 767Quiz 767Exercises 768Day 7 770Quiz 770Exercises 771Day 8 772Quiz 772Exercises 773Day 9 774Quiz 774Exercises 775Day 10 777Quiz 777Exercises 778Day 11 782Quiz 782Exercises 782Day 12 783Quiz 783Exercises 784
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Day 13 785Quiz 785Exercises 786Day 14 787Quiz 787Exercises 788Day 15 793Quiz 793Exercises 794Day 16 798Quiz 798Exercises 799Day 17 800Quiz 800Exercises 801Day 18 803Quiz 803Exercises 804Day 19 805Quiz 805Exercises 806Day 20 810Quiz 810Exercises 811Day 21 816Quiz 816Exercises 816Day 22 818Quiz 818Exercises 819Day 23 821Quiz 821Exercises 822Day 24 823Quiz 823Exercises 823Day 25 824Quiz 824Exercises 824Day 26 826Quiz 826Exercises 827Day 27 828Quiz 828Exercises 829Day 28 830Quiz 830
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Acknowledgments
I would like to acknowledge the many people who contributed to this book, both directly andindirectly First and foremost, Stacey and Robin Liberty, whose support, encouragement,and patience made it possible Also, Mike Kraley, Ed Belove, and Patrick Johnson, who create
an intellectual atmosphere at the Interchange Online Network, which makes it a gas to come
to work every day, and the many, many developers at Ziff from whom I learned whatever it
is I know about C++
I must particularly acknowledge those who taught me how to program, Skip Gilbrech andDavid McCune, and those who taught me C++, including Steve Rogers and especially StevenZagieboylo Others who contributed directly or indirectly to this book include Scott Boag,David Bogartz, Gene Broadway, Drew and Al Carlson, Frank Childs, Jim Culbert, FranDaniels, Thomas Dobbing, James Efstratiou, June Goldstein, Basha Goldstein-Weiss,Michael Griffin, David Heath, Eric Helliwell, Gisele and Ed Herlihy, Mushtaq Khalique,Matt Kingman, Steve Leland, Sangam Pant, Mike Rothman, Michael Smith, Frank Tino,Seth Weiss, Donovan White, Mark Woodbury, and Alan Zeitchek Special thanks go toWayne Wylupski and Steven Zagieboylo
Programming is as much a business and creative experience as it is a technical one, and I musttherefore acknowledge Tom Hottenstein, Jay Leve, David Rollert, David Shnaider, andRobert Spielvogel I also want to thank the many people at Sams Publishing who worked
so hard to create this book If any of what I’ve written is especially clear, it is thanks to theeditors
Finally, I’d like to thank Mrs Kalish, who taught my sixth-grade class how to do binaryarithmetic in 1965, when neither she nor we knew why
—Jesse Liberty
The first people that come to mind are my family They’ve been there through thick and thin,shared my enthusiasm and bore the brunt of my frustrations Praise God for their love anddevotion
Maggie, if I had to do it all again, I’d still say “I do.” Timmy, you’re everything I couldever want for a son; I’m very proud Heather, thank you for your kindness and gentle spirit,and for always loving Daddy even when he was cranky Alicia, though you are small, yourlove has always been big; you have been a wonderful daughter Amber, thank you for yourgift of joy and fun that helped me keep focus on the things that really matter
—J Mark Hord
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About the Authors
Jesse Liberty
Jesse Liberty has been programming computers professionally for more than 11 years He is
a Software Architect at AT&T Interchange Online Network where he was a foundingmember of the Software Development Team He is also president of The Liberty Group,Inc., and a former vice president of Citibank’s Development Division Jesse lives with hiswife, Stacey, and his daughter, Robin, in the suburbs of Cambridge, Massachusetts He can
be reached via the Internet at jl@Ichange.com, or as jl on Interchange
J Mark Hord
J Mark Hord is a C++ programmer for Musicam USA He has worked in the computerindustry since his first exposure while enlisted in the U.S Navy submarine fleet Hisexperience spans both commercial and defense companies Mark lives in New Jersey with hiswife and four children
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As you prepare for your first week of learning how to program in ANSI C++, you
will need a few things: a compiler, an editor, and this book If you don’t have a
C++ compiler and an editor, you can still use this book, but you won’t get as much
out of it as you would if you were to do the exercises
The best way to learn to program is by writing programs! At the end of each day
you will find a quiz and some exercises Be sure to take the time to answer all the
questions and to evaluate your work as objectively as you can The later lessons
build on the lessons in the earlier lessons, so be sure you fully understand the
material before moving on
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Week 1
A Note to C Programmers
The material in the first five days will be familiar to you Be sure to skim the material and to
do the exercises, to make sure you are fully up to speed before going on to Day 6 If you havehad some exposure to C++ but not object-oriented programming, you might want to skipahead and skim through Bonus Days 23 and 24 after Day 5 If you’re convinced that C++
is simply a “better C” and nothing else, then you’ll miss the point altogether To be a goodC++ programmer, you have to break out of the design paradigm used in C programming andstart thinking in objects
Where You Are Going
The first week covers the material you need to get started with programming in general, andwith C++ in particular Day 1, “Getting Started” and Day 2, “The Parts of the Program,”introduce you to the basic concepts of programming and program flow On Day 3, “Variablesand Constants,” you learn about variables and constants and how to use data in yourprograms On Day 4, “Expressions and Statements,” you learn how programs branch, based
on the data provided and the conditions encountered when the program is running On Day
5, “Functions,” you learn what functions are and how to use them, and on Day 6, “BasicClasses,” you learn about classes and objects Day 7, “More Program Flow,” teaches moreabout program flow, and by the end of the first week, you will be writing real object-orientedprograms
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Getting Started
Welcome to Teach Yourself ANSI C++ in 21 Days, Premier Edition! Today you
will get started on your way to becoming a proficient C++ programmer You’ll
learn the following topics:
■ Why C++ is the emerging standard in software development
■ The steps to develop a C++ program
■ How to enter, compile, and link your first working C++ program
A Brief History of C++
Computer languages have undergone dramatic evolution since the first
elec-tronic computers were built to assist in telemetry calculations during World
War II Early on, programmers worked with the most primitive computer
instructions, machine language These instructions were represented by long
strings of ones and zeros Soon, assemblers were invented to map machine
instructions to humanly readable and manageable mnemonics, such as ADD and
MOV
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to work with something approximating words and sentences, such as Let I = 100 Theseinstructions were translated back into machine language by interpreters and compilers Aninterpreter translates a program as it reads it, turning the programmer’s program instructions,
or code, directly into actions Compilers translate the code into an intermediary form This step is called compiling, and produces an object file The compiler then invokes a linker, which
turns the object file into an executable program Most modern compilers and linkers aredesigned to work together as a team, and the transition between the two is invisible to theprogrammer
Because interpreters read the code as it is written and execute the code on the spot, they areeasy for the programmer to work with Compilers introduce the extra steps of compiling andlinking the code, which are inconvenient, but they produce a program that runs faster When
a program is compiled, the time-consuming task of translating the source code into machinelanguage has already been accomplished
Another advantage of many compiled languages is that you can distribute the executableprogram to people who don’t have the compiler With an interpretive language, you musthave the interpreter to run the program
For many years, the principal goal of computer programmers was to write short pieces of codethat would execute quickly The program needed to be small because memory was expensive,and it needed to be fast because processing power was also expensive As computers havebecome smaller, cheaper, and faster, and as the cost of memory has fallen, these priorities havechanged Today the cost of a programmer’s time far outweighs the cost of most of thecomputers in use by businesses Well-written, easy to maintain code is at a premium “Easy
to maintain” means that as business requirements change, the program can be extended andenhanced without great expense
In the 1970s, some programmers at AT&T were working to develop tools that would maketheir jobs easier One of the members of that team, Dennis Ritchie, created a new compiled
language and called it C C became popular partially because it provided low-level ality, along with a high-level control structure A computer language is said to be a high-level
function-language if it hides the details of the computer architecture from the programmer and is
referred to as a low-level language if it does not Because C did not fit either category well, it became known as a medium-level language.
In the late 1980s, more and more computer scientists began to change the way theyapproached problems, and they began to realize that the languages they were using did notfit well with their new problem-solving paradigm Yet, because C was so popular, many wereunwilling to throw out all the old in order to start solving problems differently Instead, newversions of C began to appear that were designed with the new paradigm as their measure.Bjarne Stroustrup at AT&T invented one of those new versions of the C language Mr.Stroustrup’s new C language became known as C++
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ANSI/ISO C++
Programming languages, much like human languages, tend to change with time and even
diversify into various dialects Programmers have to learn the local version of a particular
language wherever they happen to work, only to have to learn a different version at the next
job Employers have to spend time training new programmers for the programming language
eccentricities at their company So it benefits many to strive to standardize computer
languages and limit the extent of those differences These concerns are part of the drive for
a single programming language for the United States Department of Defense, which gave
birth to the programming language, Ada
Similar concerns caused a push for the ANSI C standard some years ago Today, there is an
international effort to standardize the C++ language between the American National
Standards Institute (ANSI) and the International Standards Organization (ISO)
commit-tees The purpose of this effort, in the words of the draft standard, is “to promote portability,
reliability, maintainability, and efficient execution of C++ language programs on a variety of
computing systems.” Though the ANSI/ISO C++ standard is currently in draft form and not
yet approved as final, future changes to the draft should be minor for the most part In Teach
Yourself ANSI C++ in 21 Days we attempt to document the C++ language as it is defined in
the ANSI/ISO draft at the time of this writing
Because the ANSI/ISO standard is still in a state of change, compilervendors have not fully implemented it in their products Compilersimplement the draft standard in varying degrees, so shop around Thismeans that there might be some programs in this book that you cannotuse with your compiler
You can obtain a copy of the latest ANSI/ISO C++ draft and other useful C++ information
through the C++ Virtual Library World Wide Web (WWW) site at
http://info.desy.de/user/projects/C++.html
What Is a Program?
The word program is used in two ways: to describe individual instructions, or source code,
created by the programmer; and to describe an entire piece of executable software This
distinction can cause enormous confusion, so we will try to distinguish between the source
code on one hand, and the executable on the other
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programmer or as an executable piece of software
Source code can be turned into an executable program in two ways: Interpreters translate thesource code into computer instructions, and the computer acts on those instructionsimmediately Alternatively, compilers translate source code into a program that you can run
at a later time Although interpreters are easier to work with, most serious programming isdone with compilers because compiled code runs much faster C++ is a compiled language
Sophisticated Tools for Sophisticated
Programming
The problems programmers are asked to solve have been changing Twenty years ago,programs were created to manage large amounts of raw data The people writing the code andthe people using the program were all computer professionals Today, computers are in use
by far more people, and many know very little about how computers and programs work.These people are more interested in using computers to solve their business problems anddon’t want using the computer to get in the way of doing that
Ironically, in order to become easier to use for this new audience, programs have become farmore sophisticated Gone are the days when users typed in cryptic commands at esoteric
prompts, only to see a stream of raw data Today’s programs use sophisticated user-friendly interfaces involving multiple windows, menus, dialog boxes, and all the myriad metaphors
with which we’ve all become familiar The programs written to support this new approachare far more complex than those written just 10 years ago
As programming requirements have changed, both languages and the techniques used forwriting programs have evolved Although the complete history is fascinating, the part thatconcerns us is the transformation from procedural programming to object-oriented pro-gramming
Procedural, Structured, and Object-Oriented Programming
Until recently, programs were thought of as a series of procedures that acted upon data A
procedure, or function, was a set of specific computer instructions executed one after the
other The data was quite separate from the procedures, and the trick in programming was
to keep track of which functions called which other functions, and what data was changed
It was considered good programming practice to isolate data and the functions or proceduresthat operated on them To make sense of this potentially confusing situation, structuredprogramming was created
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A computer function or procedure is a logical collection of instructions for performing
one part of the problem being solved by the computer program A program is the
whole; a procedure or function is one part in that whole
The principal idea behind structured programming is as simple as the idea of divide and
conquer A computer program can be thought of as consisting of a set of tasks Any task that
is too complex to be described simply is broken down into a set of smaller component tasks,
until the tasks are sufficiently small and self-contained so that they can be easily understood
As an example, computing the average salary of every employee of a company is a rather
complex task You can, however, break it down into these subtasks:
1 Find out what each person earns
2 Count how many people you have
3 Total all the salaries
4 Divide the total by the number of people you have
Totaling the salaries can, itself, be broken down into more simple tasks:
1 Get each employee’s record
2 Access the salary
3 Add the salary to the running total
4 Get the next employee’s record
In turn, obtaining each employee’s record can be broken down into simpler steps as well:
1 Open the file of employees
2 Find the employee’s data in the file
3 Read the data from disk
Structured programming remains an enormously successful approach for dealing with
complex problems By the late 1980s, however, some of its deficiencies became all too clear
First, the separation of data from the tasks that manipulate the data became harder and harder
to comprehend and maintain It is natural to think of your data (employee records, for
example) and what you can do with your data (sort, edit, and so on) as related ideas
Second, programmers often had difficulty structuring a program to solve a problem while
solving the problem at the same time It was a classic inability to see the forest for the trees
Instead of solving problems, they often spent their time reinventing new ways to fit the
problem to the structure
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more interactive, event-driven approach to computer programming Event-driven means
that an event happens (the user presses a button or chooses from a menu), and the programmust respond Programs are becoming increasingly interactive, making it important todesign for that kind of functionality
Old-fashioned programs forced the user to proceed step-by-step through a series of
screens Modern event-driven programs present all the choices at once and respond
to the user’s actions
Object-oriented programming attempts to respond to these needs, providing techniques formanaging enormous complexity, achieving reuse of software components, and coupling datawith the tasks that manipulate that data
The essence of object-oriented programming is to treat data and the procedures that act upon
the data as a single object—a self-contained entity with an identity and certain characteristics
of its own
C++ and Object-Oriented Programming
C++ fully supports oriented programming, including the four pillars of
object-oriented development: encapsulation, data hiding, inheritance, and polymorphism.
Encapsulation and Data Hiding
Encapsulation and data hiding are object-oriented design techniques that programmers canuse to make interchangeable software parts The goal behind these techniques is to build self-contained objects that can be used as parts in a variety of programs Now, instead ofspecialized functions and procedures that work on a narrow collection of data, we can buildobjects that can be used to build larger objects To accomplish interchangeability, underlyingdata inside the object must be hidden so that it cannot be accidentally changed in anunexpected way Another reason for data hiding is to allow programmers to use an objectwithout needing to know all the details about how the object does what it does
The property of being a self-contained unit is called encapsulation The fact that the encapsulated unit can be used without regard to how it works is called data hiding.
When a radio enthusiast builds a radio and needs a volume control, she doesn’t create a newvolume control from scratch Instead, she simply pulls a volume control from a shelf in hergarage or at the local electronics store All the properties of the control are encapsulated inthe control object; they are not spread out through the circuits It is not necessary tounderstand how the volume control works in order to use it effectively; its data is hiddeninside its casing
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C++ supports the properties of encapsulation and data hiding through the creation of
user-defined types, called classes You’ll see how to create classes on Day 6, “Basic Classes.” After
it is created, a well-defined class acts as a fully encapsulated entity It is used as a whole unit
The actual inner workings of the class should be hidden; users of a well-defined class do not
need to know how the class works They just need to know how to use it
Inheritance and Reuse
When the engineers at Acme Motors want to build a new car, they have two choices: They
can start from scratch, or they can modify an existing model Perhaps their Star model is
nearly perfect, but they want to add a turbocharger and a six-speed transmission The chief
engineer would prefer not to start from the ground up, but rather to say, “Let’s build another
Star, but let’s add these additional capabilities We’ll call the new model a Quasar.” A Quasar
is a kind of Star, but one with new features A Quasar inherits all that a Star is and has
additional features, as well
As with other fields of engineering, software engineers have invented a name for the design
technique of making new objects from old They call this design technique inheritance The
initial object in this technique is called the base object, and the new object is called a derived
object The Quasar is derived from the Star, and thus inherits all its qualities, but it can add
to them as needed Inheritance and its application in C++ is discussed on Day 12,
“Inheritance” and Day 15, “Advanced Inheritance.”
Inheritance, in computer science, is the creation of new objects from other objects
that are similar The new object is said to inherit all that the original object contains.
The new Quasar might respond differently than a Star does when you press down on the
accelerator The Quasar might engage fuel injection and a turbocharger, while the Star would
simply let gasoline into its carburetor A user, however, does not have to know about these
differences; she can just “floor it,” and the right thing will happen depending on which car
she’s driving
How C++ Evolved
Since Bjarne Stroustrup created C++ less than a decade ago, it has gone from being used by
only a handful of developers at AT&T to being the programming language of choice for an
estimated one million developers worldwide It is expected that, by the end of the decade,
C++ will be the predominant language for commercial software development
Although it is true that C++ is a superset of C, and that virtually any legal C program is a legal
C++ program, the leap from C to C++ is very significant C++ benefited from its relationship
to C for many years because C programmers could ease into their use of C++ To really get
the full benefit of C++, however, many programmers found they had to unlearn much of what
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The question inevitably arises: Because C++ is a superset of C, should you learn C first?Stroustrup and most other C++ programmers agree that not only is it unnecessary to learn
C first, but it might be advantageous not to do so This book attempts to meet the needs ofpeople like you, who come to C++ without prior experience of C In fact, this book assumes
no programming experience of any kind
Preparing to Program
C++, perhaps more than other languages, demands that the programmer design the programbefore writing it Trivial problems, such as the ones discussed in the first few lessons of thisbook, don’t require much design However, complex problems, such as the ones professionalprogrammers are challenged with every day, do require design; and the more thorough thedesign, the more likely it is that the program will solve the problems it is designed to solve,
on time and on budget A good design also makes for a program that is relatively bug-free andeasy to maintain It has been estimated that fully 90 percent of the cost of software is thecombined cost of debugging and maintenance To the extent that good design can reducethose costs, it can have a significant impact on the bottom-line cost of the project.The first question you need to ask when preparing to design any program is, “What is theproblem I’m trying to solve?” Every program should have a clear, well-articulated goal, andyou’ll find that even the simplest programs in this book do so
The second question every good programmer asks is, “Can this be accomplished withoutresorting to writing custom software?” Reusing an old program, using pen and paper, orbuying software off the shelf are often better solutions to a problem than writing somethingnew The programmer who can offer these alternatives will never suffer from lack of work;finding less expensive solutions to today’s problems will always generate new opportunitieslater
Assuming you understand the problem, and it requires writing a new program, you are ready
to begin your design
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Your Development Environment
This book makes the assumption that your computer has a mode in which you can write
directly to the screen, without worrying about a graphical environment such as the ones in
Windows or on the Macintosh
Your compiler might have its own built-in text editor, or you might be using a commercial
text editor or word processor that can produce text files The important thing is that whatever
you write your program in, it must save simple, plain-text files with no word processing
commands embedded in the text Examples of safe editors include the Windows Notepad,
the DOS Edit command, Brief, Epsilon, EMACS, and vi Many commercial word
processors, such as WordPerfect, Word, and dozens of others, also offer a method for saving
simple text files
The files you create with your editor are called source files, and for C++, they typically are
named with the extension cpp, cp, or c In this book, all source code files are named with
the cpp extension, but check your compiler documentation for what it needs
Most C++ compilers don’t care what extension you give your sourcecode, but if you don’t specify otherwise, many will use cpp by default
Don’t Do
DO use a simple text editor to create your source code, or use the built-in editor
that comes with your compiler
DON’T use a word processor that saves special formatting characters If you do use
a word processor, save the file as ASCII text
DO save your files with the c, cp, or cpp extension.
DO check your documentation for specifics about your compiler and linker to
ensure that you know how to compile and link your programs
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Although the source code in your file may seem cryptic in the beginning, and anyone who
doesn’t know C++ will struggle to understand what it is for, it is still in what is called readable form Your source code file is not an executable program, so you cannot run it like
human-you can human-your word processor program
To turn your source code into an executable program, you use a compiler How you invokeyour compiler, and how you tell it where to find your source code, will vary from compiler
to compiler; check your documentation
After your source code is compiled, an object file is produced This file is often named withthe extension obj This is still not an executable program, however To turn this into anexecutable program, you must run your linker
Creating an Executable File with the
Linker
C++ programs are typically created by linking one or more obj files with one or more
libraries A library is a collection of linkable files that you created, that were supplied with
your compiler, or that you purchased separately All C++ compilers come with a library ofuseful functions—or procedures—and classes that you can include in your program Afunction is a block of code that performs a service, such as adding two numbers or printing
to the screen A class is a collection of data and related functions; we’ll be talking about classes
a lot, starting on Day 5, “Functions.” Libraries are the general-purpose, reusable objects youcan use for building more specialized objects We will be using an ANSI-defined standard set
of libraries throughout this book
A library is a reusable collection of data and functions, typically entire object
definitions, that you can use as interchangeable parts in your programs They are notcomplete in themselves, and they may have additional parts in them that your program doesnot use However, they are provided as general solutions to typical problems that program-mers like you have needed to solve in the past
The steps to create an executable file are as follows:
1 Create a source code file with a cpp extension
2 Compile the source code into a file with the obj extension
3 Link your obj file with any needed libraries to produce an executable program
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The Development Cycle
If every program worked the first time you tried it, that would be the complete development
cycle: Write the program, compile the source code, link the program, and run it
Unfortu-nately, almost every program—no matter how trivial—can and will have errors, or bugs, in
it Some bugs cause the compile to fail, some cause the link to fail, and some only show up
when you run the program
Whatever the type of bug you find, you must fix it This involves editing your source code,
recompiling and relinking, and then rerunning the program This cycle is represented in
Figure 1.1, which diagrams the steps in the development cycle
Compile
Compile Errors
Link
Link Errors
?
Run Program
Time Errors
Trang 40HELLO.CPP: Your First C++ Program
Traditional C programming books begin by writing the words Hello World to the screen, or
a variation on that statement This time-honored tradition is carried on here
Type the first program directly into your editor, exactly as shown When you are certain it
is correct, save the file, compile it, link it, and run it It will print the words Hello World toyour screen Don’t worry too much about how it works; this is really just to get youcomfortable with the development cycle Every aspect of this program will be covered overthe next couple of days
The listings in this book contain line numbers on the left Thesenumbers are for reference within the book They should not be typedinto your editor For example, in line 1 of Listing 1.1, you should enterthe following:
5: cout << “Hello World!\n”;
6: }
Make sure you enter this exactly as shown The only typing liberty you should take right now
is to enter any number of spaces or tabs you prefer before the cout on line 5 Pay carefulattention to the special characters The double less-than arrow symbol (<<) in line 5 is the
redirection symbol, produced on most keyboards by holding the shift key and pressing the
comma key twice Line 5 ends with a semicolon; don’t leave this off !Also, check to make sure you are following your compiler directions properly Mostcompilers link automatically, but check your documentation If you get errors, look over yourcode carefully and determine how it is different from Listing 1.1 If you see an error on line
1, such as cannot find file iostream.h, check your compiler documentation for directions
on setting up your include path or environment variables If you receive an error that there
is no prototype for main, add the line void main(); just before line 3 You need to add thisline to every program in this book before the beginning of the main function Most compilersdon’t require this, but a few do
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