#include <iostream>
using namespace std;

void SquareByValue(int x)
{
   x = x * x;
}

void SquareByReference(int& x)
{
   x = x * x;
}

void SquareByAddress(int* ptr)
{
   *ptr = *ptr * *ptr;
}

int main()
{
  int num = 5;
  cout << "1) num = " << num << '\n';

  SquareByValue(num);
  cout << "2) num = " << num << '\n';

  SquareByReference(num);
  cout << "3) num = " << num << '\n';
/*
  SquareByAddress(&num);		// pass in the address of num
  cout << "4) num = " << num << '\n';
*/
}