test13.txt

思路很清晰的c++课件。例子很简明

const double PI=3.1415926;
class Point{
protected:
   int x,y;
public:
   Point(int a,int b){ x=a;y=b; }
};
class Circle{
   int r;
public:
   Circle(int x0,int y0,int r0):Point(x0,y0)
   {
      r=r0;
   }
   double Area()
   {
      return PI*r*r;
   }
};