Write a C++ program to Make op-, ++, = a friend; use reference.

#include <iostream.h> 
 #include<conio.h> 
 class Point 
 { 
           int x, y; 
           public: 
                         Point() {} 
                         Point(int px, int py) 
                                { 
                                     x = px; 
                                     y = py; 
                                } 
                         void show() 
                               { 
                                    cout << x << " "; 
                                    cout << y << "\n"; 
                               } 
                        Point operator=(Point op2); 
                        friend Point operator++(Point &op); 
                        friend Point operator-(Point &op); 
 }; 
                       // Overload assignment for Point. 
                       Point Point::operator=(Point op2) 
                { 
                       x = op2.x; 
                       y = op2.y; 
                       return *this; // Le., return object that generated call 
                 } 
                       // Now a friend; use a reference parameter. 
                      Point operator++(Point &op) 
                { 
                         op.x++; 
                         op.y++; 
                         return op; 
                } 
                       // Make op- a friend; use reference. 
                      Point operator-(Point &op) 
                { 
                      op.x--; 
                      op.y--; 
                      return op; 
                 } 
                        void main() 
                    { 
                          clrscr(); 
                          Point ob1(10, 20), ob2; 
                          ob1.show(); 
                          ++ob1; 
                          ob1.show(); // displays 11 21 
                          ob2 = ++ob1; 
                          ob2.show(); // displays 12 22 
                          -ob2; 
                          ob2.show(); // displays 11 21 
                           getch(); 
                     }