#include <stdio.h>

/*交換函數，其形參為指針*/
void swap(int *p1, int *p2)
{
	int temp;
	/*交換指針單元所指的值*/
	temp = *p1;
	*p1 = *p2;
	*p2 = temp;
}

int main()
{
	int a,b;
	int *p1, *p2;
	a = 10; b = 20;
	/*指針賦初值，分別指向變量a和b的地址*/
	p1 = &a;
	p2 = &b;
	printf("before chaning:\n");
	printf("a = %d, b = %d\n",a, b);
	/*調用函數swap，其實參為指針*/
	swap(p1, p2);
	printf("after chaning:\n");
	/*函數調用后，能夠改變實參的值*/
	printf("a = %d, b = %d\n",a, b);
	printf("*p1 = %d, *p2 = %d\n",*p1, *p2);
}