#include<iostream.h>
class Circle
{public:
Circle(double r){radius=r}
void setradius(double r)
{radius=r;}
double getradius()
{return r;}
double zhouchang()
{
    zhouchang=2*r*3.14;return zhouchang;
}
double mianji()
{
    mianjing=r*r*3.14;return mianji;
}
private:
    double radius;
    double zhouchang;
    double mianji;
};

void main()
{Circle myCircle;
myCircle.setradius(1.1);
cout<<myCircle.zhouchang()<<endl;
cout<<myCircle.mianji()<<endl;
}

#include<iostream>
using namespace std;
class Circle
{
public:
    Circle(double r=0){radius=r;}//使用带默认参数的构造函数才能像你那样定义对象 Circle myCircle;

    void setradius(double r)
    {radius=r;}
    double getradius()
    {return radius;}
    double getzhouchang()//不能和变量名相同哈
    {
        zhouchang=2*radius*3.14;return zhouchang;
    }
    double getmianji()
    {
       mianji=radius*radius*3.14;
        return mianji;
    }
private:
    double radius;
    double zhouchang;
    double mianji;
};

void main()
{Circle myCircle;
myCircle.setradius(1.1);
cout<<myCircle.getzhouchang()<<endl;
cout<<myCircle.getmianji()<<endl;
}
而且不提倡用拼音哈 可以用匈牙利命名法 互相学习