#include<iostream>
#define MEINPI 3.1415926535897932384626433832795

using namespace std;

class Zylinder
{
    private:
        double radius;
        double hoehe;
    public:
        double berechneVolumen()
        {
            return MEINPI*radius*radius*hoehe;
        }
        void setzeRadius(double r)
        {
            radius = r;
        }
        void setzeHoehe(double h)
        {
            hoehe = h;
        }
};

int main(void)
{
    Zylinder z1;
    double r1,h1;
    cout<<"\nRadius = ?:";
    cin>>r1;
    cout<<"\nHoehe = ?:";
    cin>>h1;

    z1.setzeRadius(r1);
    z1.setzeHoehe(h1);

    cout<<"\nVolumen = "<<z1.berechneVolumen();
} 

Code 3.1-1: Volumenberechnen