Call by value and call by reference in C++

Call by value in C++

In call by value, original value is not modified.

In call by value, value being passed to the function is locally stored by the function parameter in stack memory location. If you change the value of function parameter, it is changed for the current function only. It will not change the value of variable inside the caller method such as main()

#include <iostream>  

using namespace std;  

void change(int data);  

int main()  

{  

int data = 3;  

change(data);  

cout << "Value of the data is: " << data<< endl;  

return 0;  

}  

void change(int data)  

{  

data = 5;  

}  

Output:

Value of the data is: 3

Call by reference in C++

In call by reference, original value is modified because we pass reference (address).

#include<iostream>  

using namespace std;    

void swap(int *x, int *y)  

{  

 int swap;  

 swap=*x;  

 *x=*y;  

 *y=swap;  

}  

int main()   

{    

 int x=500, y=100;    

 swap(&x, &y);  // passing value to function  

 cout<<"Value of x is: "<<x<<endl;  

 cout<<"Value of y is: "<<y<<endl;  

 return 0;  

}    

Output:

Value of x is: 100

Value of y is: 500 

                                    Watch this video for better understanding: