12.2C语言学习笔记

例1：中间变量达成数据交换

#include 
void SwapByValue(int*, int*);//定义的指针变量作为形参
int main()
{ int a = 3, b = 4;
SwapByValue(&a, &b);
printf("a=%d,b=%dn",a,b);
return 0;}
void SwapByValue(int *px, int *py)
{ int tmp;
tmp = *px;  *px = *py;  *py = tmp;//在子函数中指针变量传递的是两个整形数据的地址
printf("*px=%d,*py=%dn", *px, *py);
}

对比（传统方式）：

#include 
void SwapByValue(int, int);
int main()
{int a = 3, b = 4;
SwapByValue(a, b);
printf("a=%d,b=%dn",a,b);
return 0;}
void SwapByValue(int x, int y)
{int tmp;
tmp = x; x = y; y = tmp;
printf("x=%d,y=%dn", x, y);}

例2：简单计算

#include 
void calculate(int x, int y, int* sum, int* diff)
{
    *sum = x + y;
    *diff = x - y;
}
int main()
{   int a = 3, b = 4;
    int sum, diff;
    calculate(a, b, &sum, &diff);
    printf("%d和%d的和是:%dn", a, b, sum);
    printf("%d和%d的差是:%dn", a, b, diff);
    return 0;}