作业3.23

#include<iostream>using namespace std;class cylinder{  public:cylinder(double r,double h){radius=r;high=h;}double vol(){return 3.14*radius*radius*high;}  private:  double radius;  double high;};double main(){cylinder cyl1(3,4);cout<<"the vol of cylinder1 is "<<cyl1.vol()<<endl;return 0;}