#include <iostream>
#include <cmath>
using namespace std;

// pass by value mechanism
void addTwo(int);
// pass by value mechanism with return
int addTwoRet(int);
// pass by reference
void addTwoRef(int &);

void main(){
	
   double d = sqrt(9.0);
   cout << d << endl;
   int k = 2;
   addTwo(k);
   cout << k << endl;
   k = addTwoRet(k);
   cout << k << endl;
   // declare m which is the same as k
   // but with a different name
   int &m = k;
   cout << m << endl;
   int q = 7;
   addTwoRef(q);
   cout << q << endl;
}
void addTwo(int z){
	// z is a copy of k
	z+=2;
}
int addTwoRet(int z){
	z+=2;
	return z;
}
void addTwoRef(int &p){
	p+=2;
}