4.8 程序应用举例 [例4-16] 字符串的显示及反向显示。 #include #include /* 包含字符串库函数说明的头文件* / #include void forward_and_backwards(char line_of_char[] ,int index). /* 函数声明* / void main() { char line_of_char[80]. / *定义字符数组* / int index = 0. strcpy(line_of_char,"This is a string."). / *字符串拷贝* / forward_and_backwards(line_of_char,index). / *函数调用* / } void forward_and_backwards(char line_of_char[],int index) /*函数定义* / { if(line_of_char[index]) { printf("%c",line_of_char[index]). / *输出字符* / forward_and_backwards(line_of_char,index 1). / * 递归调用* / printf("%c",line_of_char[index]). / * 输出字符* / } } 这是一个递归函数调用的例子。程序中函数forward_and_backwards( )的功能是显示一个字符串后反向显示该字符串。 [例4-17] 计算1~7的平方及平方和。 #include # include void header(); / *函数声明* / void square(int number); void ending(); int sum; /* 全局变量* / main( ) { int index. header( ). / *函数调用* / for(index = 1.index <= 7.index ) square(index). ending( ). / *结束* / } void header() { sum = 0. /* 初始化变量"sum" */ printf("This is the header for the square program\n\n"). } void square(int number) { int numsq. numsq = number * number. sum = numsq. printf("The square of %d is %d\n",number,numsq). } void ending() { printf("\nThe sum of the squares is %d\n",sum). } 运行程序: This is the header for the square program The square of 1 is 1 The square of 2 is 4 The square of 3 is 9 The square of 4 is 16 The square of 5 is 25 The square of 6 is 36 The square of 7 is 49 The sum of the squares is 140 这个程序打印出1到7的平方值,最后打印出1到7的平方值的和,其中全局变量sum在多个函数中出现过。 全局变量在header中被初始化为零;在函数square中,sum对number的平方值进行累加,也就是说,每调用一次函数sq uare和sum就对number的平方值累加一次;全局变量sum在函数ending中被打印。