【C/C++】关于引用和指针的问题

下面的程序有错吗？为什么错了，给出正确的程序。欢迎大家给出不同的答案。

#include <iostream>
using namespace std;

void swapxy(char *a,char *b)
{
	int x = *a,y = *b;
	x = x+y;
	y = x-y;
	x = x-y;

	*a = x,*b = y;
}

void main(int argv,char argc[])
{
	char a = 'A',b = 'B';
	char &x = a,&y = b;
	cout<<"before swaping:"<<a<<" "<<b<<endl;
	swapxy(x,y);
	cout<<"after swaping:"<<a<<" "<<b<<endl;
	system("pause");
}