c++ - display the values of area for inherited classes -

in code below how can display areas of rectangle , triangle. can print strings area returned. how can print returned value functions. should change here in code, please help.

class shape {    protected:       int width, height;     public:       shape( int = 0, int b = 0) {          width = a;          height = b;       }        virtual int area() {          cout << "parent class area :" <<endl;          return 0;       } };  class rectangle: public shape {    public:       rectangle( int = 0, int b = 0):shape(a, b) { }       int area () {          cout << "rectangle class area :" <<endl;          return (width * height);       } };  class triangle: public shape{    public:       triangle( int = 0, int b = 0):shape(a, b) { }       int area () {          cout << "triangle class area :" <<endl;          return (width * height / 2);       } };  // main function program int main( ) {    shape *shape;    rectangle rec(10,7);    triangle  tri(10,5);     // store address of rectangle    shape = &rec;     // call rectangle area.    shape->area();     // store address of triangle    shape = &tri;     // call triangle area.    shape->area();     return 0; } 

change area functions below:

int rectangle::area() {     int ret = width * height;     cout << "rectangle class area : " << ret << endl;     return ret; }  int triangle::area() {     int ret = width * height / 2;     cout << "triangle class area :" << ret << endl;     return ret; }