Brian overland c++ without fear

Đây là quyển sách tiếng anh về lĩnh vực công nghệ thông tin cho sinh viên và những ai có đam mê. Quyển sách này trình về lý thuyết ,phương pháp lập trình cho ngôn ngữ C và C++.

C++ Without Fear Second Edition

C++ Without Fear Second Edition

A Beginner’s Guide That

Makes You Feel Smart

Brian Overland

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Library of Congress Cataloging-in-Publication Data

Overland, Brian R.

C++ without fear : a beginner's guide that makes you feel smart /

Brian Overland.—2nd ed.

p cm.

Includes index.

ISBN 978-0-13-267326-6 (pbk : alk paper)

1 C++ (Computer program language) I Title

QA76.73.C153O838 2011

005.13'3—dc22

2011004218 Copyright © 2011 Pearson Education, Inc.

All rights reserved Printed in the United States of America This publication is protected by right, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise For information regarding permissions, write to:

copy-Pearson Education, Inc.

Rights and Contracts Department

501 Boylston Street, Suite 900

Interlude How “Smart” Are Computers, Really? 4

Contents

Test the Program 9

Interlude What about the #include and using? 15

Interlude Why Double Precision, Not Single? 22

Interlude What about Artificial Intelligence (AI)? 35

Interlude Why Two Operators (= and ==)? 38

How It Works 47

Interlude Does “for” Always Behave Like “while”? 71

Chapter 4 Functions: Many Are Called 83

Interlude Why Global Variables at All? 95

Interlude Interlude for Math Junkies: Rest of the Proof 105

Zero-Based Indexing 119

Interlude Why Use Zero-Based Indexes? 120

Interlude What Do Addresses Look Like? 147

Pointers and Array Processing 163

Interlude How Does the Computer Translate Programs? 170

Interlude What about Escape Sequences? 177

Chapter 8 Files: Electronic Storage 197

Interlude Are “Binary Files” Really More Binary? 208

Interlude The Virtue of Predefined Constants 226

Interlude Overloading and Object Orientation 228

Handling Exceptions: A First Attempt 238

Interlude Why a “Natural” Integer? 246

Example 10.2 Setting an Array with Range-Based “for” 258

Interlude OOP…Is It Worth It? 278

Interlude Interlude for C Programmers: Structures and Classes 281

Private: Members Only (Protecting the Data) 281

Interlude Is C++ Out to Trick You with the Default Constructor? 312

Interlude The Copy Constructor and References 325

Example 12.3 Fraction Class Copy Constructor 325

Interlude Dealing with Problems in Memory Allocation 368

How It Works 369

Interlude Recursion vs Iteration Compared 401

Interlude Writing Templates in C++ 414

Creating and Using a List Class 415

Interlude Pointers vs Iterators 418

Interlude A Brief History of Polish Notation 424

Interlude Why “public” Base Classes? 437

Interlude What Is the Virtual Penalty? 455

Example 18.2 True Polymorphism: The Printable Class 466

Bitwise Operators (&, |, ^, ~, <<, and >>) 480

Appendix C Syntax Summary 491

Appendix E ASCII Codes 513

Many years ago, when I had to learn C overnight to make a living as a mer (this was before C++), I would have given half my salary to find a mentor, aperson would say, “Here are the potholes in the road errors that you are sure tomake in learning C And here’s how to steer around them.” Instead, I had tosweat and groan through every error a person could make

program-I’m not just talking about programmers who can write or writers who canprogram Each of those is rare enough Much rarer still is the person who is pro-

grammer, writer, and teacher—someone who will steer you around the

elemen-tary gotchas and enthusiastically communicate the “whys” of the language,including why this stuff is not just useful but, in its own way, kind of cool.It’s hard to find such a person But way back then, I swore this is the person I’dbecome

Later, at Microsoft, I started in tech support and testing and worked my wayinto management But my most important job (I felt) was explaining new tech-nology I was sometimes the second or third person in the world to see a new fea-ture of a programming language, and my job was to turn a cryptic spec intoreadable prose for the rest of the universe to understand I took the goal of “makethis simple” as not just a job but a mission

About This Book: How It’s Different

What’s different about this book is that I’m an advocate for you, the reader I’m

on your side, not that of some committee I’m aware of all the ways you are posed” to program and why they are supposed to be better (and I do discuss

“sup-those issues), but I’m mostly concerned about telling you what works.

This book assumes you know nothing at all about programming—that youbasically know how to turn on a computer and use a mouse For those of youmore knowledgeable, you’ll want to breeze through the first few chapters.Preface

The creators of C and C++—Dennis Ritchie and Bjarne Stroustrup, tively—are geniuses, and I’m in awe of what they accomplished But although Cand C++ are great languages, there are some features that beginners (and evenrelatively advanced programmers) never find uses for, at least not for the firstfew years I’m not afraid to tell you that information up front: what language fea-tures you can and should ignore At the same time, I’m also eager to tell youabout the elegant features of C++ that can save you time and energy.

respec-This is a book about practical examples It’s also a book about having fun! Thegreat majority of examples in this book either are useful and practical or—byusing puzzles and games—are intrinsically entertaining

So, have no fear! I won’t bludgeon you to death with overly used (and highly

abused) terms like data abstraction, which professors love but which forever

remain fuzzy to the rest of us At the same time, there are some terms—object

orientation and polymorphism—that you will want to know, and I provide

con-crete, practical contexts for understanding and using them

Onward to the Second Edition

The first edition has sold increasingly well over the years I believe that’s a ment to the variety of learning paths it supplied: complete examples, exercises,and generous use of conceptual art The second edition builds on these strengths

testa-in many ways:

◗ Coverage of new features in C++0x: This is the new specification for C++ that

will be standard by the time you have this book in your hands Compiler vendorseither have brought their versions of C++ up to this standard or are in theprocess of doing so This book covers well over a dozen new features from thisspecification in depth

◗ Examples galore, featuring puzzles and games: By the end of Chapter 2, you’ll

learn how to enter a program, barely a page long, that not only is a completegame but even has an optimal strategy for the computer Just see whether youcan beat it! But this is only the beginning This edition features puzzles andgames, much more so than the first edition

◗ Generous use of conceptual art: The use of clarifying illustrations to address

abstract points was one of the biggest strengths of the first edition This editionhas substantially more of these

◗ Even more exercises: These encourage the reader to learn in the best way by

taking apart an example that works, analyzing it, and figuring out how to modify

it to make it do your own thing

◗ No-nonsense syntax diagrams: Programming and playing games is fun, but

sometimes you need straightforward information The syntax diagrams in thisbook, accompanied by loads of examples, clarify exactly how the languageworks, statement by statement and keyword by keyword

◗ Introduction to Standard Template Library (STL): Although I lacked the space

to do a complete STL manual, this edition (unlike the first) introduces you to thewonders of this exciting feature of C++, showing how it can save you time andenergy and enable you to write powerful applications in a remarkably smallspace

◗ Expanded reference: The appendixes in the back are intended as a mini desk

ref-erence to use in writing C++ programs This edition has significantly expandedthese appendixes

◗ Essays, or “interludes” for the philosophically inclined: Throughout the book, I

detour into areas related to C++ but that impact the larger world, such as puter science, history of programming, mathematics, philosophy, and artificialintelligence But these essays are set aside as sidebars so as not to interfere withthe flow of the subject You can read them at your leisure

com-“Where Do I Begin?”

As I mentioned, this book assumes you know nothing about programming Ifyou can turn on a computer and use a menu system, keyboard, and mouse, youcan begin on page 1 If you already have some familiarity with programming,you’ll want to go through the first two or three chapters quickly

If you already know a lot about C or C++ and are mainly interested in the newfeatures of C++0x, you may want to go straight to Chapter 10, “New Features ofC++0x.”

And if you know C and are now starting to learn about object orientationwith the C++ language, you may want to start with Chapter 11, “IntroducingClasses: The Fraction Class.”

Icons, Icons, Who’s Got the Icons?

Building on the helpful icons used in the first edition, this edition provides evenmore—as signposts on the pages to help you find what you need Be sure to lookfor these symbols

These sections take apart program examples and explain, line by line, how andwhy the examples work You don’t have to wade through long programmingexamples I do that for you! (Or rather, we go through the examples together.)After each full programming example, I provide at least one exercise, and usuallyseveral, that builds on the example in some way These encourage you to alterand extend the programming code you’ve just seen This is the best way to learn.

The answers can be found on the book’s Web site (www.informit.com/title/

This icon indicates a place where a keyword of the language is introduced and itsusage clearly defined

C++0x 䊳 This icon is used to indicate sections that apply only to versions of C++compliant with the new C++0x specification Depending on the version of C++you have, either these sections will apply to you or they won’t If your version isnot C++0x-compliant, you’ll generally want to skip these sections

What Is Not Covered?

Relatively little, as it turns out The two features not covered at all are bit fieldsand unions Although these features are useful for some people, their applicationtends to be highly specialized—limited to a few special situations—and not par-ticularly useful to people first learning the language Of course, I encourage you

to learn about them on your own later

Another area in which I defer to other books is the topic of writing your owntemplate classes, which I touch on just briefly in Chapter 16 Without a doubt,the ability to write new template classes is one of the most amazing features ofstate-of-the-art C++, but it is a very advanced and complex topic For me tocover it adequately and exhaustively could easily have taken another 400 or 500pages!

Fortunately, although templates and the Standard Template Library (STL) areadvanced subjects, there are some good books on the subject—for example,

C++ Templates: The Complete Guide, by David Vandevoorde and Nicolai M.

Josuttis; STL Tutorial and Reference Guide: C++ Programming with the Standard

Template Library, Second Edition, by David R Musser, Gillmer J Derge, and Atul

Saini; and Effective STL: 50 Specific Ways to Improve Your Use of the Standard

Template Library, by Scott Meyers.

And remember that Chapter 16 does introduce you to using STL, which vides extremely useful, existing templates for you to take advantage of

pro-Getting Started with C++: A Free Compiler

Although this edition doesn’t come with a CD with a free compiler on it, that is

no longer necessary You can download some excellent shareware (that is, free)versions of C++ from the Internet that not only have a free compiler (that’s theapplication that translates your programs into machine-readable form) but also

a very good development environment And they install easily

To download this free software, start by going to the book’s Web site:

www.informit.com/title/9780132673266.

As mentioned earlier, you will also find downloadable copies of all the fullprogram examples in the book, as well as answers to exercises

A Final Note: Have Fun!

Once again, there is nothing to fear about C++ Yes, there are those nasty holes I started out discussing, but remember, I’m going to steer you aroundthem Admittedly, C++ is not a language for the weak of heart; it assumes youknow exactly what you’re doing But it doesn’t have to be intimidating I hopeyou use the practical examples and find the puzzles and games entertaining This

pot-is a book about learning and about taking a road to new knowledge, but morethan that, it’s a book about enjoying the ride

Acknowledgments

Brian Overland published his first article in a

pro-fessional math journal at age 14

After graduating from Yale, he began working

on large commercial projects in C and Basic,including an irrigation-control system used allover the world He also tutored students in math,computer programming, and writing, as well aslecturing to classes at Microsoft and at the com-munity-college level On the side, he found an out-let for his lifelong love of writing by publishingfilm and drama reviews in local newspapers Hisqualifications as an author of technical books arenearly unique because they involve so much real programming and teachingexperience, as well as writing

In his 10 years at Microsoft, he was a tester, author, programmer, and ager As a technical writer, he became an expert on advanced utilities, such as thelinker and assembler, and was the “go-to” guy for writing about new technology.His biggest achievement was probably organizing the entire documentation setfor Visual Basic 1.0 and having a leading role in teaching the “object-based” way

man-of programming that was so new at the time He was also a member man-of the VisualC++ 1.0 team

Since then, he has been involved with the formation of new start-up nies (sometimes as CEO) He is currently working on a novel

compa-About the Author

to use it to solve the fundamental programming tasks That’s the approach here.

In the first couple of sections, I review the basic concepts of programming Ifyou’ve programmed in any language, you might want to skip these But if youstick around, I promise to not be too long-winded

Thinking Like a Programmer

Programming may not be exactly like any activity you’ve ever done Basically,you’re just giving instructions—but doing so in a logical, systematic manner

Computers Do Only What You Tell Them

Computers do only what you tell them: This is the most important rule in thisbook, especially if you are new to programming By using a computer language,such as C++, Visual Basic, Pascal, or FORTRAN, you give the computer a list of

things to do; this is the program.

A computer needs information, of course—that’s program data But it also

needs to know what to do with that data The instructions that tell it what to do

are called program code.

Determine What the Program Will Do

So, to get a computer to do anything, it has to be told exactly what to do

So far, you’ve probably used a computer by running programs that other people

have written for you To this extent, you’ve been an end user—or user, for short.

By writing programs yourself, you’ll promote yourself into the next higherechelon of computer people Now, you’ll decide what a program does You’llmake things happen

But a computer—more so than Dustin Hoffman in Rain Man—is the

ulti-mate idiot savant It can never guess what you want It can never make dent judgments It is extremely literal and will carry out precisely what you say,

indepen-no matter how stupid Therefore, you have to be careful to say what you mean.You can’t even give the computer a command that might seem relatively clear

to a human, such as “Convert a number from Celsius to Fahrenheit for me.” Eventhat’s too general Instead, you have to be more specific, writing down steps such

as these:

1 Print the “Enter Celsius temperature:” message

2 Get a number from the keyboard and store it in the variable ctemp.

3 Convert to Fahrenheit by using the formula ftemp = (ctemp * 1.8) + 32.

4 Print the “The Fahrenheit temperature is:” message

5 Print the value of the variable ftemp.

If you have to go through this much trouble just to do something simple, whyeven bother? The answer is that once a program is written, you can run it overand over And though programs take time to write, they usually execute at light-ning speed

Write the Equivalent C++ Statements

After you’ve determined precisely what you want your program to do, step, you need to write down the equivalent C++ statements A statement isroughly the C++ equivalent of a sentence in English

step-by-For example, say you want your program to do the following:

1 Print the “The Fahrenheit temperature is:” message

2 Print the value of the variable ftemp.

You’d translate these steps into the following C++ statements:

cout << "The Fahrenheit temperature is: ";

cout << ftemp;

Remember, the goal of programming is to get the computer to do a series ofspecific tasks But the computer understands only its own native language—

machine code—which consists of 1s and 0s Back in the 1950s, programmers did

write out instructions in machine code, but this was difficult and time-consuming

To make things easier, computer engineers developed programming guages such as FORTRAN, Basic, and C, which enable humans to write pro-grams bearing at least some resemblance to English

lan-To write a program, you may want to start by writing pseudocode—an

approach I often use in this book Pseudocode is similar to English, but itdescribes the action of the program in a systematic way reflecting the logical flow

of the program For example, here’s a simple program written in pseudocode:

If a is greater than bPrint “a is greater than b.”

ElsePrint “a is not greater than b.”

Once you’ve written pseudocode, you’re not far from having a C++ program.All you need to do is look up the corresponding C++ statement for each action:

if (a > b)cout << "a is greater than b.";

elsecout << "a is not greater than b.";

The advantage of a programming language is that it follows rules that allow

no ambiguity C++ statements are so precise that they can be translated into the1s and 0s of machine code without guesswork

It should come as no surprise that programming languages have strict rules ofsyntax These rules are more consistent, and usually simpler, than rules in ahuman language From time to time, I summarize these rules For example,

here’s if-else syntax:

The application that translates C++ statements into machine code is called a

compiler I’ll have a lot more to say about compilers in the upcoming section

“Building a C++ Program.” First, however, let’s review some key definitions

yw

ord

Some Nerdy Definitions—A Review

I like to avoid jargon I really do But when you start learning programming, youenter into a world that requires new terminology The following are some defin-itions you need to survive in this world

Interlude

When I ran a computer lab in Tacoma, Washington, some years ago, I cameacross some interesting characters, some of them right off the street One ofthem was a rotund little man in a straw hat, ill-matching clothes, old shoes,

and a big smile, who carried around a copy of The Daily Racing Form like it

was the Bible

He came up to me every other day with his horse-racing newspaper “I gotthis idea,” he kept saying “We’ll make a million All we have to do is put this

information into the computer and have it pick horses I’ll supply The Daily

Racing Form You write the program We’ll be rich!” I smiled but mumbled

something about feasibility problems

What he forgot—or probably never understood—is that no real edge exists inside the computer itself There’s no magical being inside that

knowl-answers your questions like the ship’s computer in Star Trek Just entering

raw data into a computer does nothing What a computer needs first is the

right program a series of instructions that tells it how to move, copy, add,

subtract, multiply, or otherwise evaluate data

The real trick in getting a computer to properly pick winning horses at

the racetrack, of course, would be to come up with the right algorithm an

algorithm being a systematic, step-by-step technique for evaluating data andgetting a result, that is to say, the right formula If you could come up withthe right algorithm for picking horses, I don’t deny it could make you rich.But in that case, finding a computer would be the least of your problems.You could use any computer as long as it could hold the data required

As for finding a programmer, well, if you could get such a person tobelieve you really had the right algorithm, it would simply be a matter ofoffering to split the first 10 million dollars in winnings I know any number

of people who would go for that

Or better yet, you could use the techniques in this book to write the gram yourself

pro-How “Smart” Are Computers, Really?

application

Essentially the same thing as a program but seen from a user’s point of view Anapplication is a program that a user runs to accomplish some task A wordprocessor is an application; so is an Internet browser or a database manager

Even a compiler (defined in a moment) is an application, but of a very special

kind, because it’s used by programmers To put the matter simply, when yourprogram is written, built, and tested, it’s an application

code

Another synonym for “the program,” but from the programmer’s point of view

The use of the term code stems from the days in which programmers wrote in

machine code Each machine instruction is encoded into a unique combination

of 1s and 0s and is therefore the computer’s code for doing some action

Programmers have continued to talk about “code” even when using languages

such as C++, Java, FORTRAN, or Visual Basic (See the definition of source

code.) Also, the term code is used to differentiate between the passive

informa-tion in a program (its data) and the part of the program that performs acinforma-tions(its code)

compiler

The language translator that takes C++ statements (that is, C++ source code) asinput and outputs the program in machine-code form This is necessary,because the computer itself—its central processing unit (CPU)—only under-stands machine code

data

Information operated on by a program At its most basic level, this informationconsists of words and/or numbers

machine code

The CPU’s native language, in which each computer instruction consists of a

unique combination (or code) of 1s and 0s It is still possible to program in

machine code, but this requires looking up each instruction, as well as havingelaborate knowledge of the CPU’s architecture

Languages such as C++ provide a way to write programs that is closer to lish but still logically precise enough to be translated into machine code

A series of instructions to be carried out by a computer along with initial data

As I mentioned earlier, a program can take time to write, but once it’s completed,

it usually executes at lightning-fast speed and can be run over and over

source code

A program written out in a high-level language such as C++ Source code needs

to be translated into machine code before it can actually be run on a computer.Machine code is typically represented in hexadecimal (base 16), so it lookssomething like this:

resem-if (salary < 0)print_error_message();

statement

A simple statement usually corresponds to one line of a C++ program, and it isterminated by a semicolon (just as an English statement is terminated by aperiod) But C++ supports compound statements, just as English does, andthese can take up multiple lines Most C++ statements perform an action,although some perform many actions

user

The person who runs a program—that is, the person who utilizes the computer

to do something useful, such as edit a text file, read email, explore the Internet,

or balance a checkbook The more official name for user is end user.

When I was at Microsoft, the user was the person who caused most of thetrouble in the world, but he or she was also the person who paid the bills Even ifthis hypothetical person was a nontechnical “bozo,” there would be no Microsoftwithout users buying its products So when you start designing serious pro-grams, it’s important that you carefully consider the needs of the user

What’s Different About C++?

Most of the things I’ve just said about C++ apply to other programming

guages such as Pascal, Java, FORTRAN, and Basic These are all high-level

lan-guages, meaning they do not correspond closely to machine code but use

keywords (such as “if ” and “while”) that bear some resemblance to English.Each language was developed for a different purpose Basic was designed to beeasy to learn and to use As a result, it permitted loose syntax that unfortunatelycan lead to bad programming habits Still, Microsoft developed Visual Basic into

a powerful, convenient, quick application-building tool for Microsoft Windowsand cleaned up some of its sloppiness

Pascal was developed for use in academic environments, to teach cated programming concepts Pascal is more elaborate than Basic, but it cannot

sophisti-do everything that C or C++ can

The legendary computer scientist Dennis Ritchie originally designed C forhelp in writing operating systems It’s a clean language that supports shortcutsand makes it possible to write more concise programs The straightforward butcomprehensive syntax of C has proven popular with programmers throughoutthe world Another advantage of C is that it imposes fewer restrictions thanother languages do

So what about C++?

The major difference between C and C++ is that C++ adds the ability to do

object-oriented programming This is an approach especially well-suited to

work-ing with complex systems, such as graphical user interfaces and network ronments As an object-oriented programmer, you would ask the following:

envi-1 What are the major kinds of data (that is, information) in the problem to be solved?

2 What operations should be defined for each kind of data?

3 How do the data objects interact with each other?

In learning object-oriented programming, I’ve found it’s easier if you’ve tered basic statement syntax first Therefore, I don’t focus on object orientationuntil Chapter 11

mas-But I do introduce some objects—pieces of data that can respond to

opera-tions—early in the book For example, in this chapter, I use cout, a data object

not part of the C language In C, you’d print information by calling a function,

which is a predefined series of statements But when you use cout, you’re sending

data to an object that—in a real sense—knows how to display information.