//函数的定义和声明举例:
#include<stdio.h>
#include<stdlib.h>
int sum(int a, int b) //形式参数
{
int x = a*b;
int y = a - b;
int c = x+y;
return c;
}
int main()
{
int d = sum(2, 5); //实际参数
int xy = sum(10, 9);
printf("d=%d \n", d);
printf("xy=%d \n", xy);
system("pause");
return 0;
}