C语言实现 用函数实现两个数的交换

#include <stdio.h>
#include <stdlib.h>
int main()
{
 int a, b;
 int change_num(int a, int b);//声明change_num函数
 printf("please enter two numbers:");
 scanf("%d,%d", &a, &b);
 change_num(&a,&b);//调用change_num函数
 printf("%d %d\n", a, b);
 system("pause");
 return 0;
}
int change_num(int *px, int *py)//定义change_num函数
{
 int temp;
 temp = *px;
 *px = *py;
 *py = temp;
}