virtual functions

#include<iostream>
#include<cmath>
using namespace std;
double PI=3.1416;
class shape
{
public:
    virtual void print()=0;
};
class point:virtual public shape
{
protected:
    double x ,y ;
public:
    point(){x=0;y=0;}
    void setpoint(double a , double b) {x=a; y=b;}
    point(double a , double b){x=a; y=b;}
    double distance(const point p)
    {
        return sqrt((x-p.x)*(x-p.x)+(y-p.y)*(y-p.y));
    }
    void print()
    {
        point p;
        cout<<"x = " << x << ","<<"y= " <<y<<endl;
        cout<<"the distance from the origin is : "<<distance(p)<<endl;
    }
};
class circle : public point
{
protected:
    double r;
public:
    circle(double a , double b ,double c ): point (a,b)
    {
        r=c;
    }
    double perimeter()
    {
        return (2*PI*r);
    }
    double area()
    {
        return (PI*PI*r);
    }
    void  print()
    {
        point :: print();
        cout<<"the coordinates of the center are : (" << x<< ","<<y <<")"<<endl;
        cout<<"the radius is : " <<r <<endl;
        cout<<"the area is :"<<area()<<endl;
        cout<<"the perimeter is :"<<perimeter()<<endl;
    }
};
class cylinder : public circle
{
protected:
    double h;
public:
    cylinder (double a , double b , double c , double d): circle (a,b,c)
    {
        h=d;
    }
    double surface()
    {
        return (2*PI*r*(r+h));
    }
    double volume()
    {
        return (PI*r*r*h);
    }
    void print()
    {
        circle::print();
        cout<<"the height is :"<<h <<endl;
        cout<<"the surface is : "<<surface()<<endl;
        cout<<"the volume is : "<<volume()<<endl;
    }
};
int main()
{
    //part 2
    cout<<"part 2 :"<<endl;
    const int size =100;
    shape *s[size];
    int choice=0;
    int i=0;
    double x,y,r,h;
    while (choice !=4)
    {
        cout<<endl<<endl<<"Choose between:\npoint(1)-circle (2)-cylinder (3)- quit (4)\n ";
        cin>>choice;
        switch (choice)
        {
        case 1:
            cout<<"you chose a point! :"<<endl;
            cout<<"enter the point coordinates x and y : "<<endl;
            cout<<"x=";cin>>x;
            cout<<"y=";cin>>y;
            s[i]= new point(x,y);
            i++;
            break;
        case 2:
            cout<<"you chose a circle! :"<<endl;
            cout<<"enter the center coordinates x and y :"<<endl;
            cout<<"x=";cin>>x;
            cout<<"y=";cin>>y;
            cout<<"enter the radius :";cin>>r;
            s[i]=new circle(x,y,r);
            i++;
            break;
        case 3:
            cout<<"you chose a cylinder! :"<<endl;
            cout<<"enter the center coordinates x and y :"<<endl;
            cout<<"x=";cin>>x;
            cout<<"y=";cin>>y;
            cout<<"enter the radius :";cin>>r;
            cout<<"enter the height :";cin>>h;
            s[i]=new cylinder (x,y,r,h);
            i++;
            break;
        case 4:
            for (int j=0 ; j<i ;j++)
            {
                cout<<"you entered the following data in choice #"<<j<<endl;
                s[j]->print();
                cout<<endl<<endl;
            }
            break;
        default:
            cout<<"incorrect input ! ";
            break;

        }
    }
    for (int j=0;j<i;j++)
    {
        delete s[j];
    }

return