Pass By Referance

//*******************************************************
// We introduce the concept of pass by referance 
// The difference between a method which is 
//implemented by using pass by referance and which is not
//*******************************************************
#include <cstdlib>
#include <iostream>
using namespace std;
//Defining a method which calculates the square of given number
int getSquare1(int num1);
int getSquare2(int &num2);
int main(int argc, char *argv[])
{
    // We define two integer for our two different getSquare method
    int num1 = 2,num2 = 2;
    cout<<"num1 was initially "<<num1<<endl;
    cout<<"num2 was initially "<<num2<<endl;
    // We call the methods
    cout<<"Square of num1 is "<<getSquare1(num1)<<endl;
    cout<<"Square of num2 is "<<getSquare2(num2)<<endl;
    //After calling square methods
    cout<<"num1 is "<<num1<<endl;
    cout<<"num2 is "<<num2<<endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}
int getSquare1(int num1){
    num1 = num1*num1;
    return num1;    
}
int getSquare2(int &num2){
    num2 = num2*num2;
    return num2;    
}
//************************************************************
//The difference between the methods is that the first one do not
//use the variable it creates a variable instead of the num1 but 
//the second method it uses the num2 since we send  adress of the 
//variable to the method so it uses num2 not creates a copy of num2.
//Thus, num2 changes.
//**************************************************************