//friend function example source code//role of friend function.#include 
     
      using namespace std;class x{  protected:  int x1;  public:  x(int a1):x1(a1){}};class y:public x{  private:  int y1;  public:  y(int a1, int a2):x::x(a1),y1(a2){ }  friend void disp(y&);};void disp(y &os){    cout << "x1 = " << os.x1 << "  y1 = " << os.y1 << endl;} int main(){    y oop(12,24);    disp(oop);    return 0;}