ampersand

#include <iostream>
using namespace std;

	void square(int& a)
		{
		a = a * a;
			return;
		}

//THIS IS AN EXAMPLE OF FAILURE.
/*
	int main()
	{
		int x = 1;
		int y = 2;
		square(x + y);
		cout << x;
		return 0;
	}
*/

	int main()
	{
		int x = 1;
		int y = 2;
		int z = x + y;
		square(z);
		cout << x;
		return 0;
	}