练习2: 通过交换函数的实现，学习指针的用法。

练习2 指针的学习 看下面的程序,要明确明白为何swap1不起作用,swap2有效.

#include "stdafx.h"void swap1(int a, int b){int temp = b;b = a;a = temp;}void swap2(int *a, int *b){int temp = *b;*b = *a;*a = temp;}int main(){int a= 7, b= 8;swap1(a,b);printf("swap1 a=%d,b=%d\n",a,b);swap2(&a,&b);            printf("swap2 a=%d,b=%d\n",a,b);return 0;}