C++编程基础：计算机科学与工程导论

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"C++ for Computer Science and Engineering, 4th Edition" 是一本面向计算机科学与工程领域的C++编程教程，由Vic Broquard撰写。本书覆盖了从基础编程概念到高级特性的广泛主题，旨在帮助初学者逐步掌握C++语言。在书中，作者首先介绍了编程的基本概念，让读者理解编程语言的基础知识。第二章“数值处理”讲解了如何在C++中进行数学运算和数据处理。第三章“额外的处理细节”深入探讨了更复杂的编程技巧和细节，如内存管理和错误处理。第四章“决策”涵盖了条件语句（如if-else）和逻辑操作，这些都是编写有选择性行为的程序所必需的。第五章“文件和循环”介绍输入/输出操作以及如何使用循环结构（如for, while）来重复执行代码。第六章和第七章“编写自己的函数”和“更多关于函数”的内容，详细解释了函数的定义、调用以及如何利用函数模块化程序。第八章“字符处理和do case”则关注字符操作和基于字符的控制流（如switch-case语句）。第九章至第十三章是数组、字符串、多维数组和结构体的深入研究，这些是C++中处理数据集合的关键工具。在这些章节中，读者将学习如何声明、初始化和操作这些数据类型。书中的三个附录分别提供了使用不同版本的Microsoft Visual C++编译器的指南，包括2005、2002和6.0版本，这对于使用Windows环境下的C++开发至关重要。最后，书后附有索引，方便读者查找特定主题。这本书是学习C++编程的全面教程，适合计算机科学和工程专业的学生，或者对C++感兴趣的初学者。它不仅讲解了语言的基础，还涉及了实际编程中可能遇到的各种问题，包括文件操作、循环控制、函数编程和数据结构，以及如何使用流行的C++开发环境。通过本书，读者可以系统地学习并掌握C++编程技能，为未来在计算机科学和工程领域的工作打下坚实基础。

Introduction to Programming

Chapter 1 — Introduction to Programming

Section A: Basic Theory

Introduction

There are few areas of study that have more specialized terms and abbreviations to know than in

the computer field. As you study the text, key words and abbreviations are given good action

definitions as they occur. If a section of a chapter is blank in your mind, stop and look back

earlier and see if you can find a word or abbreviation that is not fully understood. Once the word

is fully understood, reread that blank section and it should now make sense.

At the end of each chapter are two practice sections designed to solidify the theory just

studied. The “Design Exercises” enhance your problem solving skills. The “Stop! Do These

Exercises Before Programming” exercises illustrate many of the common errors that a

programmer can make. Thus, if you work these exercises before you begin the actual

programming problems, you should make far fewer goofs, should have a much more enjoyable

time doing the programming, should greatly reduce the amount of time it takes to do your

assignments and should definitely lower the frustration level.

What is a Computer?

A definition of a computer is an electronic device that can input data, process data and output

data, accurately and at great speed. Data are any kind of information that can be codified in some

manner and input into the computer. Normally, we think of data as facts and numbers such as a

person’s name and address or the quantity or cost of an item purchased. However, data can also

be graphical images, sound files, movies and more.

A computer is capable of inputting information such as the quantity ordered and the cost

of that item. Processing data means to do something with it. Often we think of processing as

performing some kind of calculations. If the quantity and cost have been input, then the obvious

calculation would be to multiply cost times quantity to produce the total cost. However,

processing data can mean more than just calculations. Perhaps you have entered the series of

friends and their phone numbers. Processing the data can also mean sorting the friends’

information into alphabetical order by last names. Finally, to be useful, the computer needs to be

able to output information, the results, to the user in an accurate and timely manner. The user is

anyone that is making use of the results that the computer is producing.

Introduction to Programming

However, an abacus can input, process and output data. There must be more in this

definition. It is the qualifier, accurately and at great speed, that makes computers so powerful.

Let’s look at each of these in turn.

A computer is accurate and reliable; they do not make mistakes. But it did not used to be

this way. Back in the first generation of computers in the early 1950's, computers were built from

some 18,000 vacuum tubes. And tubes frequently burned out forcing their replacement.

Statistically, when one has 18,000 of these tubes in one machine, one expects one tube failure

every fifteen seconds! This is where the idea that computers are not reliable has its genus. There

was no reliability in those days. However, with modern computers now built from silicon and

germanium integrated circuits or chips (a device consisting of a number of connected electronic

circuit elements such as transistors fabricated on a single chip of silicon crystal), the failure rate

is about one chip failure ever thirty-three million hours of operation. Of course, if you drop a

computer or run it during an electrical storm, you can significantly shorten its lifetime. Thus,

modern computers are reliable. However, the software that runs on them is not necessarily error

proof.

The other qualifier is at great speed. Just how fast is a computer? Let’s compare the time

that it takes various computers to add two integer whole numbers. The unit of time measurement

is the nanosecond which is 10 of a second, or 1/1,000,000,000 of a second. Electricity travels

-9

approximately 11.4 inches down a copper wire in a nanosecond. The following chart is an

approximation of how long it takes some computers to add two numbers. (MHz is short for

megahertz or a million cycles per second, GHz is gigahertz (1024 MHz), and ns is

nanoseconds.)

IBM-PC 4.77 MHz 600 ns

386 33 MHz 60 ns

486 100 MHz 10 ns

Pentium 200 MHz 5 ns

P-3 500 MHz 2 ns

P-4 2 GHz .5 ns

In other words, if you have one of the newer Pentium-3 500 MHz machines, in one

second the computer could perform many billions of additions. (Note that the addition instruction

is one of the fastest instructions the computer has. Many other instructions take substantially

longer to perform.)

Thus, it is the ability of the modern computer to perform reliably and to perform at great

speed that has made it so powerful.

Introduction to Programming

Computers have a fixed set of instructions that they can perform for us. The specific

instruction set depends upon the make and model of a computer. However, these instructions can

be broadly grouped into four basic categories:

Math instructions

Comparison instructions

Movement of data instructions

Input and output instructions

When one thinks of math instructions, the add, subtract, multiply and divide operations

immediately come to mind. However, for a mathematician, there are more complex math

operations as well, such as finding the trigonometric sine of an angle or the square root of a

number. Comparison instructions permit the computer to tell if one number is greater than, less

than or equal to another number. The computer can move data from one location in its memory

to another area. And of course, the computer can input and output data.

And that is all that a computer knows how to do. I sometimes joke that a computer is

basically a “moronic idiot.” That is, it is an “idiot” because of its limited instruction set, in other

words, what it knows how to do. The “moronic” adjective comes from the fact that the computer

always attempts to do precisely what you tell it to do. Say, for example, you tell the computer to

divide ten by zero, it tries to do so and fails at once. If you tell the computer to calculate a

person’s wages by multiplying their hours worked by their hours worked, say, forty hours this

week, the computer accurately and at great speed does the multiply instruction, and outputs their

pay as $1600!

Thus, we have this rule: If you tell the computer to do something stupid, the computer

accurately and at great speed does that stupid action! Your idea of a computer either

malfunctioning or making a mistake is likely coming from this aspect.

What is a program? A computer program is a series of instructions that tell the computer

every step to take in the proper sequence in order to solve a problem for a user. A programmer

is one who writes the computer program. When the computer produces a wrong or silly result, it

can be traced to an improper sequence of instructions or incorrect data being input to the

program. That is, the responsibility or blame lies on either the original programmer who wrote

out the instructions for the computer to follow or the user who has entered incorrect data.

For example, the latest Mars explorer satellite, after flawlessly traveling all the way to

Mars, disintegrated on attempting to go into orbit around the planet. The reason NASA

discovered is that the computer program controlling the satellite expected measurements to be in

English units and someone supplied those measurements in the metric system.

Thus, I have a new term for programs that have one or more errors in them — “mostly

working software.” When a program has an error in it, that error is often called a “bug.” And the

process of getting all of the errors out of a program is called debugging. The term originates in

Introduction to Programming

the first generation of computers when someone removed a fly that had gotten into the computer

circuitry and shorted it out - they were “debugging” the computer. In fact, mostly working

software is a pet peeve of mine. Mostly working software — a program with one or more errors

in it — is indicative of a programmer who has not done their job thoroughly for whatever

reason. What would you think about having an operation done by a mostly working surgeon?

Designing Solutions — the Cycle of Data Processing

Perhaps the single most important aspect of solving a problem on the computer is the initial

design phase in which one lays out with paper and pencil the precise steps the computer must

take. Nearly every significant program follows the same fundamental design and it is called the

Cycle of Data Processing, Figure 1.1.

The Cycle of Data Processing is Input, Process, Output. First the computer must input a

set of data on which to work. Once the data has been input into the computer, it can then process

that data, often performing some calculations on that information. When the calculations are

finished, the computer outputs that set of data and the results.

For example, suppose that we wanted to write a program that would calculate someone’s

wages. First, the computer must be instructed to input the person’s hours worked and their pay

rate. Next, the computer uses the values it has just input to calculate the wages. Now that the

wages are known, the computer can output the answer.

The Cycle of Data Processing is called IPO for short. IPO is the most basic design of a

program. Thus, when you are confronting a computer problem to solve, IPO is the starting point!

Input a set of information first. Then do the requisite processing steps using that information.

Last, output the results.

Also notice that in general, once that set of data and results have been output, the program

would repeat the entire process on the next set of data until there are no more sets of data to be

processed. It will be several chapters before we can implement all these steps.

Introduction to Programming

Any deviation from the IPO sequence generally yields silly results. Suppose that someone

tried to write a program to calculate a person’s wages by doing OPI instead? That is, have the

program output the answer before it knew what the hours that were worked or who was the

person for whom the wages were to be found! Nonsense. Have the program calculate the pay

before it has input the hours worked? How can it? You see, worked in reverse, it just makes no

sense at all.

Occasionally, by accident someone writes an IP program. That is, it inputs the data and

does the calculations, but fails to output the result. For example, you want a soda, so you input

your quarters into the pop machine, Input. You press the button and the internal machinery makes

lots of noise as it processes your request. But no can of soda ever appears, no Output! Or take a

PO program. You walk by the soda machine and all of a sudden you hear it making noises and a

can of soda appears! Or you walk by a piano and it starts playing — spooky when there is no

input! Occasionally, someone writes an O program by accident. Suppose the program needed to

print some headings at the top of a page and suppose the programmer made a booboo and

continually printed headings over and over and over. You would have an O program. Or take a P

program, the program just calculates, calculates, calculates, endlessly. This is sometimes called

an infinite processing loop.

Whenever you are trying to design a program, remember that it usually must follow the

IPO cycle. Now there are some exceptions, but they are rare. A possible exception might be

producing a mathematical table of trigonometric function values. For example, suppose that you

wanted to produce a table of the values of the sine and cosine of all angles from zero to ninety

degrees. In such a case, there would be no input, just a process-output series as the program

calculated each set of results and displayed them.

Building a Program

The computer internally operates on the binary number system. In the binary number system,

the only valid digits are 0 and 1. For example, if you add in binary 1 plus 1, you get 10, just as if

you added 9 + 1 => 10 in the decimal or base 10 system.

Why does the computer use binary? Electronic circuits can either have some electricity in

them or not. If a circuit element, such as a transistor, has electricity, it can be said to contain a 1;

if none, then a 0. This is the basis for computer operations. The actual instructions that make up a

program are all in binary, long strings of binary digits. But no one wants to try to write out these

long tedious series of 1's and 0's to try to direct the computer to solve a problem. Rather a high-

level language is used. In this case, we use the C++ language.

In a high-level language, we use various symbols and mathematical notations to create the

program which is called the source program. A source program is the precise series of high-

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