Area of Circle and rectangle

/*      Area of Circle and Rectangle   */
/*            Language: C++            */



#include <iostream.h>
#include <conio.h>
#define pi 3.14


class area
{
    protected:
        float area;

    public:

        virtual float area_calc()
        {}
};

class rectangle:public area
{

        float length,breadth;

        public:

            rectangle()
            {
                cout<<"\n\nEnter Length of the Rectangle";
                cin>>length;
                cout<<"\nEnter Breadth of the Rectangle";
                cin>>breadth;
            }
            float area_calc()
            {
                return length*breadth;
            }

};

class circle:public area
{
    float radius;

    public:
        circle()
        {
            cout<<"\n\nEnter Radius of the Circle: ";
            cin>>radius;
        }
        float area_calc()
        {
            return pi*radius*radius;
        }
};

int main()
{
    system("cls");
    area *area_ptr;


    cout<<"\n\nCalculating area of a rectangle....\n\n";

            rectangle rect1;
            area_ptr=&rect1;
            cout<<"\n\nArea of the given rectange is: "<<area_ptr->area_calc();

    cout<<"\n\nCalculating area of a Circle....\n\n";

            circle circle1;
            area_ptr=&circle1;
            cout<<"\n\nArea of the given circle is: "<<area_ptr->area_calc();
    getch();
    return 0;

}