Pass by reference using references : reference parameter « Function « C++ Tutorial

1. C++ Tutorial
2. Function
3. reference parameter

#include <iostream>
 
 void swap(int &x, int &y);
 
 int main()
 {
     int x = 5, y = 10;
 
     std::cout << "Main. Before swap, x: " << x 
                                 << " y: " << y << "\n";
     swap(x,y);
     std::cout << "Main. After swap, x: " << x 
                                << " y: " << y << "\n";
     return 0;
 }
 
 void swap (int &rx, int &ry)
 {
     int temp;
 
     std::cout << "Swap. Before swap, rx: " << rx 
                                 << " ry: " << ry << "\n";
 
     temp = rx;
     rx = ry;
     ry = temp;
 
     std::cout << "Swap. After swap, rx: " << rx 
                                << " ry: " << ry << "\n";
 }

Main. Before swap, x: 5 y: 10
Swap. Before swap, rx: 5 ry: 10
Swap. After swap, rx: 10 ry: 5
Main. After swap, x: 10 y: 5