/**
 * file: main.c
 * author: 简单教程(www.twle.cn)
 *
 * Copyright © 2015-2065 www.twle.cn. All rights reserved.
 */

#include<stdio.h>
#define exchange(a,b) { int t;t=a;a=b;b=t;}//注意放在一行里
int main()
{
    int x=10;
    int y=20;
    printf("x=%d; y=%d\n",x,y);
    exchange(x,y);
    printf("x=%d; y=%d\n",x,y);
    return 0;
}

x=10; y=20
x=20; y=10