C primer plus, 4th ed 2002

C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents... C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents... C Primer Plus, Fourth EditionBy Stephen Prata Table

Publisher : Sams Publishing Pub Date : September 19, 2001 ISBN : 0-672-32222-6

The for Loop

More Assignment Operators: +=, -=, *=, /=, %=

Adding else to the if Statement

Let's Get Logical

A Word-Count Program

The Conditional Operator: ?

Loop Aids: continue and break

Multiple Choice: switch and break

The goto Statement

Altering Variables in the Calling Function

Pointers: A First Look

Communicating with Files

Standard I/O

A Simple-Minded File-Condensing Program

File I/O: fprintf() , fscanf() , fgets() , and fputs()

Adventures in Random Access: fseek() and ftell()

Manifest Constants: #define

Using Arguments with #define

Index

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

Copyright © 2002 by Sams Publishing

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

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Figures and illustrations clarify concepts that are

difficult to grasp in words alone

Highlight boxes summarize the main features of Cfor easy reference and review

improve your understanding of C

To gain the greatest benefit, you should take as active

a role as possible in studying the topics in this book.Don't just read the examples, enter them into your

system and try them C is a very portable language,but you may find differences between how a programworks on your system and how it works on ours

Experimentchange part of a program to see what theeffect is Modify a program to do something slightlydifferent Ignore the occasional warnings and see whathappens when you do the wrong thing Try the

questions and exercises The more you do yourself,the more you will learn and remember

I hope that you'll find this newest edition an enjoyableand effective introduction to the C language

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C99 It was adopted by the International Organizationfor Standardization (ISO) and the International

Expanded character support

Boolean support

Variable-length arrays

consolidated and expanded, and Chapter 12, "StorageClasses, Linkage, and Memory Management,"

incorporates dynamic memory allocation into the

discussion of C storage classes and memory

management Numerous other changes and additionshave been incorporated in response to reader requests

to make this edition an even more effective learningtool

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

Stephen Prata is a professor of physics and

astronomy at the College of Marin in Kentfield,

California, where he teaches astronomy, physics, andprogramming He received his B.S from the

California Institute of Technology and his Ph.D fromthe University of California, Berkeley His associationwith computers began with the computer modeling ofstar clusters Stephen has authored or coauthored over

a dozen books, including C++ Primer Plus and Unix Primer Plus.

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

welcome your comments You can fax, email, or write

me directly to let me know what you did or didn't likeabout this bookas well as what we can do to make ourbooks stronger

share them with the author and editors who worked on

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

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Most languages aim to be useful, but they often have

other concerns The main goal for Pascal, for instance,was to provide a sound basis for teaching good

programming principles BASIC, on the other hand,

was developed to resemble English so that it could belearned easily by students unfamiliar with computers.These are important goals, but they are not always

compatible with pragmatic, workaday usefulness C'sdevelopment as a language designed for

modern-day languages of choice

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

Chapter 1 Getting Ready

Why C?

During the past three decades, C has become one ofthe most important and popular programming

languages It has grown because people try it and like

it In the past decade, many have moved from C to themore ambitious C++ language, but C is still an

C is a modern language incorporating the control

features found desirable by the theory and practice ofcomputer science Its design makes it natural for users

to use top-down planning, structured programming,and modular design The result is a more reliable,

understandable program

Efficiency

of an operating system¡ªsuch as Windows or OS

X¡ªtypically are not portable

Because of C's close ties with UNIX, UNIX systemstypically come with a C compiler as part of the

packages Linux installations also usually include a Ccompiler Several C compilers are available for

personal computers, including PCs running variousversions of Windows and Macintoshes So whetheryou are using a home computer, a professional

workstation, or a mainframe, the chances are goodthat you can get a C compiler for your particular

result, when you use FORTRAN on a UNIX machine,ultimately a C program has done the work of

producing the final executable program C programshave been used for solving physics and engineering

movies such as Gladiator.

Programmer Oriented

C is oriented to fulfill the needs of programmers Itgives you access to hardware, and it enables you tomanipulate individual bits in memory It has a richselection of operators that allow you to express

yourself succinctly C is less strict than, say, Pascal, inlimiting what you can do This flexibility is both anadvantage and a danger The advantage is that manytasks, such as converting forms of data, are much

simpler in C The danger is that with C, you can makemistakes that are impossible in some languages Cgives you more freedom, but it also puts more

responsibility on you

Also, most C implementations have a large library ofuseful C functions These functions deal with manyneeds that a programmer commonly faces

Shortcomings

C does have some faults Often, as with people, faultsand virtues are opposite sides of the same feature Forexample, we've mentioned that C's freedom of

of pointers (something you can look forward to

learning about in this book), in particular, means thatyou can make programming errors that are very

difficult to trace As one computer preliterate oncecommented, the price of liberty is eternal vigilance

C's conciseness combined with its wealth of operatorsmake it possible to prepare code that is extremely

difficult to follow You aren't compelled to write

obscure code, but the opportunity is there After all,what other language has a yearly Obfuscated Codecontest?

There are more virtues and, undoubtedly, a few morefaults Rather than delve further into the matter, let'smove on to a new topic

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

C as the preferred language for producing word

processing programs, spreadsheets, compilers, andother products These companies know that C

What's good for companies and C veterans is good forother users, too More and more computer users haveturned to C to secure its advantages for themselves.

Despite the popularity of newer languages, such asC++ and Java, C remains a core skill in the softwarebusiness, typically ranking in the top ten of desiredskills In particular, C has become popular for

programming embedded systems That is, it's used toprogram the increasingly common microprocessorsfound in automobiles, cameras, DVD players, and

other modern conveniences Also, C has been makinginroads in FORTRAN's long dominance of scientificprogramming Finally, as befits a language created todevelop an operating system, it plays a strong role inthe development of Linux Thus, the first decade ofthe twenty-first century finds C still going strong

In short, C is one of the most important programminglanguages and will continue to be so If you want ajob writing software, one of the first questions youshould be able to answer yes to is "Oh say, can youC?"

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

Chapter 1 Getting Ready

What Computers Do

Now that you are about to learn how to program in C,you probably should know a little about how

computers work This knowledge will help you

understand the connection between writing a program

in C and what eventually takes place when you runthat program

Modern computers have several components Thecentral processing unit, or CPU, does most of the

computing work The random-access memory, or

RAM, serves as a workspace to hold programs andfiles The permanent memory, typically a hard disk,remembers those programs and files, even if the

computer is turned off And various peripherals¡ªsuch

as the keyboard, mouse, and monitor¡ªprovide forcommunication between the computer and you TheCPU processes your programs, so let's concentrate onits role

and executes it It fetches the next instruction from

memory and executes it, and so on (A gigahertz CPUcan do this about a billion times a second, so the CPUcan lead its boring life at a tremendous pace.) The

CPU has its own small workspace, consisting of

several registers, each of which can hold a number.

One register holds the memory address of the next

instruction, and the CPU uses this information to fetchthe next instruction After it fetches an instruction, theCPU stores the instruction in another register and

instruction code, or what is called machine language.

One consequence of how computers work is that ifyou want a computer to do something, you have tofeed a particular list of instructions (a program) telling

it exactly what to do and how to do it You have tocreate the program in a language that the computerunderstands directly (machine language) This is adetailed, tedious, exacting task Something as simple

as adding two numbers together would have to be

broken down into several steps:

1 Copy the number in memory location 2000 to register 1.

And you would have to represent each of these

instructions with a numeric code!

something you'd like to do, you'll be sad to learn thatthe golden age of machine-language programming islong past But if you prefer something a little moreenjoyable, open your heart to high-level programminglanguages

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C Primer Plus, Fourth EditionBy Stephen Prata Table of Contents

Chapter 1 Getting Ready

High-Level Computer Languages and Compilers

High-level programming languages, such as C,

simplify your programming life in several ways First,you don't have to express your instructions in a

numeric code Second, the instructions you use aremuch closer to how you might think about a problemthan they are to the detailed approach a computer

uses Rather than worry about the precise steps a

particular CPU would have to take to accomplish aparticular task, you can express your desires on a

more abstract level To add two numbers, for

example, you might write the following:

total = mine + yours;

Seeing code like this, you have a good idea what itdoes; looking at the machine-language equivalent ofseveral instructions expressed in numeric code is

easier to program in than are machine languages

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at that process soon, and you'll see that it is straightforward andsensible First, to give you an overview of programming, let'sbreak down the act of writing a C program into seven steps (see

Figure 1.3) Note that this is an idealization In practice,

particularly for larger projects, you would go back and forth,using what you learned at a later step to refine an earlier step

Figure 1.3 The seven steps of programming.

Naturally enough, you should start with a clear idea of what youwant the program to do Think in terms of the information yourprogram needs, the feats of calculation and manipulation theprogram needs to do, and the information the program shouldreport back to you At this level of planning, you should be

thinking in general terms, not in terms of some specific

computer language

Step 2: Design the Program

to do, you should decide how the program will go about it

What should the user interface be like? How should the program

be organized? Who will the target user be? How much time doyou have to complete the program?

You also need to decide how to represent the data in the

program and, possibly, in auxiliary files, and which methods touse to process the data When you first learn programming in C,the choices will be simple, but as you deal with more complexsituations, you'll find that these decisions require more thought.Choosing a good way to represent the information can often

Step 3: Write the Code

Now that you have a clear design for your program, you canbegin to implement it by writing the code That is, you translateyour program design into the C language Here is where youreally have to put your knowledge of C to work You can sketch

your programming environment We'll present the details forsome common environments soon In general, you use a text

printf("So you have %d dog(s)!\n", dogs); return 0;

a particular machine language C compilers also incorporatecode from C libraries into the final program; the libraries

contain a fund of standard routines, such as printf() and

scanf(), for your use (More accurately, a program called a

linker brings in the library routines, but the compiler runs the

linker for you on most systems.) The end result is an executablefile containing code that the computer understands and that youcan run

The compiler also checks that your program is valid C If thecompiler finds errors, it reports them to you and doesn't produce

an executable file Understanding a particular compiler's

complaints is another skill you will pick up

Step 5: Run the Program