#include <iostream>
using namespace std;



void functionOne(int data)
{
     cout << "Value of data passed into functionOne: " << data << endl;
     data = data * 2;
     cout << "Value of data at end of functionOne: " << data << endl;
}

void functionTwo(int & data)
{
     cout << "Value of data passed into functionTwo: " << data << endl;
     data = data * 2;
     cout << "Value of data at end of functionTwo: " << data << endl;
}

void functionThree(int *data)
{
     cout << "Value of data passed into functionThree: " << *data << endl;
     *data = *data * 2;
     cout << "Value of data at end of functionThree: " << *data << endl;
}

int main(int argc, char* argv[])
{
     int x = 5;

     // pass by value
     cout << "Value of x before calling functionOne: " << x << endl;
     functionOne(x);    
     cout << "Value of x after calling functionOne: " << x << endl << endl;
    
     // pass by reference     
     cout << "Value of x before calling functionTwo: " << x << endl;
     functionTwo(x);    
     cout << "Value of x after calling functionTwo: " << x << endl << endl;

     // pass "with pointer"
     cout << "Value of x before calling functionThree: " << x << endl;
     functionThree(&x);    
     cout << "Value of x after calling functionThree: " << x << endl;
}