Why does this program show 3 outputs, also why does b override a?

Question

#include "stdafx.h"
#include <iostream>

using namespace std;

void silly(int & a, int & b)
{
    a=10;
    b=20;
    cout << a << "" << b << endl;
}


void main()
{
    int z=30;
    silly(z,z);
    cout << z << endl;
    system("Pause");

}

The output for this is:

2020 20

Why are there 3 outputs, and why does b override a?

I'm asking because this is part of homework and I don't exactly understand the passing of variables especially strings/arrays.

Answer 1

You are passing the reference of z to the silly() function.

When you change the value of a or b (both references to z) in silly(), it changes the value of z.

So, at this line:

  cout << a << "" << b << endl;

the value of z is 20, hence the output.