用c++编写程序：求圆形circle的周长和面积，请编写一个基于对象的程序。数据成员包括R（半径）

Question

要求用成员函数实现以下功能：
1、由键盘输入一个圆的半径；
2、计算圆的周长和面积

Answer 1

#include <iostream.h>

#define PI 3.141593

class Circle
{
public:
Circle():m_radius(1)
{
}

~Circle()
{
}

void SetRadius(double radius)
{
if(radius<1e-6) radius=1e-6;
m_radius=radius;
}

double GetRadius()
{
return m_radius;
}

double Perimeter()
{
return 2*PI*m_radius;
}

double Area()
{
return PI*m_radius*m_radius;
}
private:
double m_radius;
};

int main()
{
Circle c;
double r;
cout<<"Please input R:"<<endl;
cin>>r;
c.SetRadius(r);
cout<<"It's perimeter is "<<c.Perimeter()<<endl;
cout<<"It's perimeter is "<<c.Area()<<endl;

return 0;
}