C语言英文ch06

1、Chapter 6Modularity Using Functions: Part IFunction and Parameter DeclarationsA function that is called into action by its reference in another function is a called function(被调用函数被调用函数:一个函数通过被其他函数引用而起作用一个函数通过被其他函数引用而起作用)A function that calls another function is referred to as the calling function(调用

2、函数调用函数)Function and Parameter Declarations调用和传递数据到函数调用和传递数据到函数Function and Parameter DeclarationsFunction Prototypes(函数原型函数原型)The declaration statement for a function is referred to as a function prototype (一个函数的声明语句称为函数原型一个函数的声明语句称为函数原型) Declares the data type of the value that will be directly ret

3、urned by the function(函数原型声明将被这个函数直接返回的数值的数函数原型声明将被这个函数直接返回的数值的数据类型据类型) Declares the data type of the values that need to be transmitted to the called function when it is invoked(在它被调用时需要传递给被在它被调用时需要传递给被调用函数的数值的数据类型调用函数的数值的数据类型) returnDataType functionName (argument data types);Calling a FunctionArg

4、uments(参数参数): items enclosed in parentheses in a function call statement（函数调用语句中被圆括号附上的条目）（函数调用语句中被圆括号附上的条目） Other terms used for arguments are actual arguments(实际参数实际参数)and actual parameters(实参实参)Pass by value(按值传递按值传递): when a function receives copies of the values in each argument and must determ

5、ine where to store them before it does anything else(函数只是接受这些变量的数值复制品，并且在它做其他任函数只是接受这些变量的数值复制品，并且在它做其他任何事情之前必须确定在哪里存储这些数值。何事情之前必须确定在哪里存储这些数值。) Also referred to as call by value(数值调用数值调用)Calling a FunctionCalling a FunctionFunction Header LineFunction header(函数首部函数首部) : identifies the data type of th

6、e return value, provides the function with a name, and specifies the number, order, and type of values expected by the functionFunction body(函数体函数体): operates on the passed data and returns, at most, one valueThe argument names in the header line are known as parameters(参参数数)or formal parameters(形参形

7、参)and formal arguments(形式参数形式参数)Function Header LineFunction Header LineSome programmers prefer to put all called functions at the top of a program and make main() the last function listedEach C function is a separate and independent entity with its own parameters and variables(每个每个C 语言的函数都是分开的和独立的，

8、有它语言的函数都是分开的和独立的，有它们自己的参数和变量。们自己的参数和变量。) Nested functions are not permitted(决不允许把一个函数嵌套在另一决不允许把一个函数嵌套在另一个函数里面。个函数里面。 )Function Header LineEnds with a semicolonDoes not end with a semicolonFunction Header LineBasic (good) programming structure:preprocessor directivessymbolic constantsfunction prototy

9、pes can be placed hereint main() function prototypes can be placed here variable declarations; other executable statements; return value;Placement of Statements(语句的放置语句的放置)Returning a ValueFrom its side of the return transaction, the called function must provide: Data type of the returned value, whi

10、ch is specified in the functions header line Actual value being returned, which is specified by a return statementReturning a ValueReturning a ValueTo return a value, use a return statement return (expression); /or, return expression; The expression is evaluated first; its value is then automaticall

11、y converted to the return values data type as specified in the functions header line before being sent back to the calling function (表达式首先被计算。然后，表达式的数值在被送回到调用函数之前表达式首先被计算。然后，表达式的数值在被送回到调用函数之前自动地转换为在函数首部行中定义的返回值的数据类型。自动地转换为在函数首部行中定义的返回值的数据类型。)Returning a ValueFailure to exactly match the return value

12、 with the functions declared data type can lead to undesired results Return value is converted to the data type declared in the functions header line（返回的数值总是被转换为函数首部行中声明的数据类（返回的数值总是被转换为函数首部行中声明的数据类型）型）Returning a ValueStandard Library FunctionsThe standard library consists of 15 header filesBefore u

13、sing these functions, you must know The name of each available function The arguments required by each function The data type of the result (if any) returned by each function A description of what each function does How to include the library containing the desired functionT#include Mathematical Lib

14、rary FunctionsMathematical Library FunctionsThe rand() FunctionsRandom numbers(随机数随机数)are a series of numbers whose order cannot be predicted（次序不能被预知的一系列数字）（次序不能被预知的一系列数字）All C compilers provide a function for creating random numbers: rand() ，defined in the stdlib.h header file rand() produces rando

15、m numbers in the range 0 rand() RAND_MAX（RAND_MAX是一个取决于编译器的在头文件中被定义的符号常量。）是一个取决于编译器的在头文件中被定义的符号常量。）Scaling(比例缩放比例缩放)The method for adjusting the random numbers produced by a random-number generator to reside within a specified range is called scaling(调调整由随机数发生器产生的随机数在一个指定的范围内的方法叫比例缩整由随机数发生器产生的随机数在一个

16、指定的范围内的方法叫比例缩放放)To scale a random number as an integer value between 1 and N:1 + (int)rand() % NTo produce a random integer between the numbers a and b:a + (int)(rand() % (b - a + 1)Input/Output Library Functionsgetchar() can be used for single character inputinchar=getchar();scanf(“%c”,&inchar);putchar() expects a single character argument