Contrasting Parameters: Value vs. Reference

#include <iostream.h>

void valFunction(int a);
void refFunction(int &a);

void main(void)
{
  int i = 5;
	
  cout << "i = " << i << endl;

  valFunction(i);

  cout << "i = " << i << endl;

  refFunction(i);

  cout << "i = " << i << endl;
}

void valFunction(int x)
{
  x = 10;
}

void refFunction(int &x)
{
  x = 12;
}

Output:
i = 5
i = 5
i = 12