C语言编程基础

需积分: 0 88 浏览量更新于2024-07-29 收藏 733KB PDF 举报

"The C programming Language" 《C程序设计语言》是一本由Brian W. Kernighan和Dennis M. Ritchie共同撰写的经典教材，于1988年由Prentice-Hall出版社出版，是C语言学习者的必备参考书。书中的内容涵盖了C语言的基础到进阶知识，旨在提供一个教程式的引导，帮助读者掌握C语言编程的核心概念和技术。 1. **序言**：作者们可能在序言中介绍了编写本书的背景、目的以及C语言的重要性，对于初学者来说，这部分可以帮助他们理解学习C语言的意义和价值。 2. **第一版前言**：可能讲述了第一版的出版情况和当时C语言的环境，对后续版本的修订提供了历史背景。 3. **引言**：简要介绍C语言的基本特点和学习路径，为读者进入正文做好准备。 4. **第1章：教程式介绍**： - **开始**：讲解如何设置开发环境，编译和运行第一个C程序。 - **变量与算术表达式**：介绍C语言中的基本数据类型和算术运算符。 - **for语句**：解释for循环的工作原理和使用场景。 - **符号常量**：讨论#define预处理指令和const关键字定义常量。 - **字符输入输出**：涵盖标准输入输出函数，如scanf和printf。 - **示例程序**：通过几个简单的程序实例（文件复制、字符计数、行计数、词计数）来实践这些概念。 5. **数组**：介绍一维和多维数组的声明、初始化和操作。 6. **函数**：讲解函数的定义、调用以及参数传递（按值传递）。 7. **字符数组**：涉及字符串和字符串处理函数。 8. **外部变量与作用域**：讨论全局变量和局部变量的区别及其作用范围。 9. **第2章：类型、运算符和表达式**： - **变量名**：规定了变量命名的规则。 - **数据类型与大小**：详述整型、浮点型、字符型等数据类型的表示和内存占用。 - **常量**：涵盖整型、浮点型、字符型和字符串常量。 - **声明**：解释变量声明的语法和作用。 - **算术运算符**：包括加减乘除、取模等运算。 - **关系和逻辑运算符**：介绍比较和逻辑运算符。 - **类型转换**：讨论自动类型转换和强制类型转换。 - **自增自减运算符**：讲解++和--的用法。 - **位运算符**：涵盖位与、位或、位异或和位非操作。 - **赋值运算符与表达式**：讨论复合赋值运算符和表达式中的副作用。 - **条件表达式**：介绍三目运算符的使用。 - **运算符优先级和结合性**：解释运算符执行的顺序。 10. **第3章：控制流程**： - **语句和块**：介绍语句的结构和代码块的概念。 - **if-else**：讲解条件判断语句的用法。 - **else-if**：阐述多条件分支的实现。 - **switch**：介绍switch语句的用法。 - **循环：while和for**：解释两种不同类型的循环结构。 - **do-while**：讲解do-while循环的特点。 - **break和continue**：介绍跳出循环的控制语句。 - **goto和标签**：讨论goto语句的使用，虽然不推荐但有时是必要的。 11. **第4章：函数和**：这部分可能会继续深入讨论函数，包括函数指针、递归、参数传递（按引用传递）等内容。这本书不仅适合初学者，也对有经验的程序员有价值，因为它深入浅出地解释了C语言的各个方面，使读者能够理解和掌握这个强大的编程工具。通过阅读本书，读者可以建立起坚实的C语言基础，并有能力编写出高效、可靠的C程序。

A sequence of characters in double quotes, like "hello, world\n", is called a character

string or string constant. For the moment our only use of character strings will be as

arguments for printf and other functions.

The sequence \n in the string is C notation for the newline character, which when

printed advances the output to the left margin on the next line. If you leave out the \n

(a worthwhile experiment), you will find that there is no line advance after the output

is printed. You must use \n to include a newline character in the printf argument; if you

try something like

printf("hello, world

");

the C compiler will produce an error message.

printf never supplies a newline character automatically, so several calls may be used to

build up an output line in stages. Our first program could just as well have been

written

#include <stdio.h>

main()

{

printf("hello, ");

printf("world");

printf("\n");

}

to produce identical output.

Notice that \n represents only a single character. An escape sequence like \n provides a

general and extensible mechanism for representing hard-to-type or invisible

characters. Among the others that C provides are \t for tab, \b for backspace, \" for the

double quote and \\ for the backslash itself. There is a complete list in Section 2.3.

Exercise 1-1. Run the ``hello, world'' program on your system. Experiment with leaving

out parts of the program, to see what error messages you get.

Exercise 1-2. Experiment to find out what happens when prints's argument string

contains \c, where c is some character not listed above.

1.2 Variables and Arithmetic Expressions

The next program uses the formula

C=(5/9)(

F-32) to print the following table of Fahrenheit

temperatures and their centigrade or Celsius equivalents:

1 -17

20 -6

40 4

60 15

80 26

int lower, upper, step;

The type int means that the variables listed are integers; by contrast with float, which means

floating point, i.e., numbers that may have a fractional part. The range of both int and float

depends on the machine you are using; 16-bits ints, which lie between -32768 and +32767, are

common, as are 32-bit ints. A float number is typically a 32-bit quantity, with at least six

significant digits and magnitude generally between about 10

-38

and 10

C provides several other data types besides int and float, including:

char

character - a single byte

short

short integer

long

long integer

double

double-precision floating point

The size of these objects is also machine-dependent. There are also arrays, structures

and unions of these basic types, pointers to them, and functions that return them, all of

which we will meet in due course.

Computation in the temperature conversion program begins with the assignment

statements

lower = 0;

upper = 300;

step = 20;

which set the variables to their initial values. Individual statements are terminated by semicolons.

Each line of the table is computed the same way, so we use a loop that repeats once

per output line; this is the purpose of the while loop

while (fahr <= upper) {

...

}

The while loop operates as follows: The condition in parentheses is tested. If it is true (fahr is less

than or equal to upper), the body of the loop (the three statements enclosed in braces) is executed.

Then the condition is re-tested, and if true, the body is executed again. When the test becomes

false (fahr exceeds upper) the loop ends, and execution continues at the statement that follows the

loop. There are no further statements in this program, so it terminates.

The body of a while can be one or more statements enclosed in braces, as in the

temperature converter, or a single statement without braces, as in

while (i < j)

i = 2 * i;

In either case, we will always indent the statements controlled by the while by one tab stop (which

we have shown as four spaces) so you can see at a glance which statements are inside the loop.

The indentation emphasizes the logical structure of the program. Although C compilers do not

care about how a program looks, proper indentation and spacing are critical in making programs

easy for people to read. We recommend writing only one statement per line, and using blanks

around operators to clarify grouping. The position of braces is less important, although people

hold passionate beliefs. We have chosen one of several popular styles. Pick a style that suits you,

then use it consistently.

Most of the work gets done in the body of the loop. The Celsius temperature is

computed and assigned to the variable celsius by the statement

celsius = 5 * (fahr-32) / 9;

The reason for multiplying by 5 and dividing by 9 instead of just multiplying by 5/9 is that in C, as

in many other languages, integer division truncates: any fractional part is discarded. Since 5 and 9

are integers. 5/9 would be truncated to zero and so all the Celsius temperatures would be reported

as zero.

This example also shows a bit more of how printf works. printf is a general-purpose

output formatting function, which we will describe in detail in Chapter 7. Its first

argument is a string of characters to be printed, with each % indicating where one of

the other (second, third, ...) arguments is to be substituted, and in what form it is to be

printed. For instance, %d specifies an integer argument, so the statement

printf("%d\t%d\n", fahr, celsius);

causes the values of the two integers fahr and celsius to be printed, with a tab (\t) between them.

Each % construction in the first argument of printf is paired with the corresponding

second argument, third argument, etc.; they must match up properly by number and

type, or you will get wrong answers.

By the way, printf is not part of the C language; there is no input or output defined in C

itself. printf is just a useful function from the standard library of functions that are

normally accessible to C programs. The behaviour of printf is defined in the ANSI

standard, however, so its properties should be the same with any compiler and library

that conforms to the standard.

In order to concentrate on C itself, we don't talk much about input and output until

chapter 7. In particular, we will defer formatted input until then. If you have to input

numbers, read the discussion of the function scanf in Section 7.4. scanf is like printf,

except that it reads input instead of writing output.

There are a couple of problems with the temperature conversion program. The simpler

one is that the output isn't very pretty because the numbers are not right-justified.

That's easy to fix; if we augment each %d in the printf statement with a width, the

numbers printed will be right-justified in their fields. For instance, we might say

printf("%3d %6d\n", fahr, celsius);

to print the first number of each line in a field three digits wide, and the second in a field six digits

wide, like this:

0 -17

20 -6

40 4

60 15

80 26

100 37

...

The more serious problem is that because we have used integer arithmetic, the Celsius

temperatures are not very accurate; for instance, 0

F is actually about -17.8

C, not -17. To get

more accurate answers, we should use floating-point arithmetic instead of integer. This requires

some changes in the program. Here is the second version:

#include <stdio.h>

/* print Fahrenheit-Celsius table

for fahr = 0, 20, ..., 300; floating-point version */

main()

{

float fahr, celsius;

float lower, upper, step;

lower = 0; /* lower limit of temperatuire scale */

upper = 300; /* upper limit */

step = 20; /* step size */

fahr = lower;

while (fahr <= upper) {

celsius = (5.0/9.0) * (fahr-32.0);

printf("%3.0f %6.1f\n", fahr, celsius);

fahr = fahr + step;

}

This is much the same as before, except that fahr and celsius are declared to be float and the

formula for conversion is written in a more natural way. We were unable to use 5/9 in the previous

version because integer division would truncate it to zero. A decimal point in a constant indicates

that it is floating point, however, so 5.0/9.0 is not truncated because it is the ratio of two

floating-point values.

If an arithmetic operator has integer operands, an integer operation is performed. If an

arithmetic operator has one floating-point operand and one integer operand, however,

the integer will be converted to floating point before the operation is done. If we had

written (fahr-32), the 32 would be automatically converted to floating point.

Nevertheless, writing floating-point constants with explicit decimal points even when

they have integral values emphasizes their floating-point nature for human readers.

The detailed rules for when integers are converted to floating point are in Chapter 2.

For now, notice that the assignment

fahr = lower;

and the test

while (fahr <= upper)

also work in the natural way - the int is converted to float before the operation is done.

The printf conversion specification %3.0f says that a floating-point number (here fahr) is

to be printed at least three characters wide, with no decimal point and no fraction

剩余257页未读，继续阅读

jaderat

粉丝: 1

《the c programming language》(CLH)

The C Programming Language(2nd Edition) 中文完整版PDF

The C Programming Language(C程序设计语言).pdf

The C programming language

the c programming language

The C Programming language

the C Programming language

unity的UI框架，简单好用，已在成熟项目中使用

IMG_1399.PNG

【毕业设计】java-springboot-vue教师工作量管理系统实现源码（完整前后端+mysql+说明文档+LunW）.zip

最新资源