Reference as function argument does not need to initialize __ function

#include <iostream>
using namespace std;

void swap (int a, int b)
{
	int c=0;
	c = A;
	A = b;
	b = C;
}
void Swap1 (Int*a, int*b)
{
	int c=0;
	c = *a;
	*a = *b;
	*b = C;
}
Reference as a function parameter does not require initialization of
void swap2 (int &a, int &b)
{
	int c=0;
	c = A;
	A = b;
	b = C;
}
int main ()
{
	int x =10;
	int y =20;

	Swap (x,y);
	printf ("x=%d,y=%d\n", x,y);
	Swap1 (&x,&y);
	printf ("x=%d,y=%d\n", x,y);
	A is the alias of X, B is the alias of Y, the modification of a is the modification to x
	swap2 (x,y);
	printf ("x=%d,y=%d\n", x,y);

	System ("pause");
	return 0;
}