程序代码：

/*两个数互换*/

# include <stdio.h>
void huhuan(int *a , int *b )
{  
    int  t;
        t = *a; //a是int *， *a是int。t必须是int
        *a = *b;
        *b = t; //b是b的值所在的地址。*b是 b代表的地址贮存的值：
  
   return ;
}
int main(void)
{  
    int a;
    int b;
    a = 3;
    b = 5;
    huhuan(&a, &b);
    printf("a = %d\nb = %d\n",a,b);


    return 0;
}