这个c++程序编译的异常很奇怪~

这个c++程序编译的错误很奇怪~~
我在用win32 application 新建一个工程时，把下面的文件加进去，编译后就会有错误。

//POINT.H
#ifndef _POINT_H
#define _POINT_H

class Point
{public:
  Point(float=0,float=0);
  void setPoint(float,float);
  float getX() const {return x;}
  float getY() const {return y;}
  friend ostream & operator<<(ostream &,const Point &);
protected:
  float x,y;
};
#endif


//CIRCLE.H
#include "point.h"
#ifndef _CIRCLE_H
#define _CIRCLE_H

class Circle:public Point
{public:
  Circle(float x=0,float y=0,float r=0);
  void setRadius(float);
  float getRadius() const;
  float area () const;
  friend ostream &operator<<(ostream &,const Circle &;
protected:
  float radius;
};
#endif

//CYLINDER.H
#include "circle.h"
#ifndef _CYLINDER_H
#define _CYLINDER_H

class Cylinder:public Circle
{public:
  Cylinder (float x=0,float y=0,float r=0,float h=0);
  void setHeight(float);
  float getHeight() const;
  float area() const;
  float volume() const;
  friend ostream& operator<<(ostream&,const Cylinder&);
protected:
  float height;
};
#endif


//POINT.CPP
#include "point.h"
Point:Point(float a,float b)
{x=a;y=b;}

void Point::setPoint(float a,float b)
{x=a;y=b;}

ostream & operator<<(ostream &output,const Point &p)
{output<<"["<<p.x<<","<<p.y<<"]"<<endl;
return output;
}


//CIRCLE.CPP
//#include <iostream.h>
#include "circle.h"
Circle::Circle(float a,float b,float r):Point(a,b),radius(r){}

void Circle::setRadius(float r)
{radius=r;}

float Circle::getRadius() const {return radius;}

float Circle::area() const
{return 3.14159*radius*radius;}

ostream &operator<<(ostream &output,const Circle &c)
{output<<"Center=["<<c.x<<","<<c.y<<"], r="<<c.radius<<", area="<<c.area()<<endl;
return output;
}


//CYLINDER.CPP
#include "cylinder.h"

Cylinder::Cylinder(float a,float b,float r,float h)
  :Circle(a,b,r),height(h){}

void Cylinder::setHeight(float h){height=h;}

float Cylinder::getHeight() const {return height;}

float Cylinder::area() const
{ return 2*Circle::area()+2*3.14159*radius*height;}

float Cylinder::volume() const
{return Circle::area()*height;}

ostream &operator<<(ostream &output,const Cylinder& cy)
{output<<"Center=["<<cy.x<<","<<cy.y<<"], r="<<cy.radius<<", h="<<cy.height
  <<"\narea="<<cy.area()<<", volume="<<cy.volume()<<endl;
return output;
}

///main.cpp
#include <iostream>  
using namespace std;  
#include "point.h"
#include "circle.h"
#include "cylinder.h"
#include "point.cpp"
#include "circle.cpp"
#include "cylinder.cpp"
int main()
{Cylinder cy1(3.5,6.4,5.2,10);
cout<<"\noriginal cylinder:\nx="<<cy1.getX()<<", y="<<cy1.getY()<<", r="
  <<cy1.getRadius()<<", h="<<cy1.getHeight()<<"\narea="<<cy1.area()
  <<", volume="<<cy1.volume()<<endl;

cy1.setHeight(15);
cy1.setRadius(7.5);
cy1.setPoint(5,5);
cout<<"\nnew cylinder:\n"<<cy1;
Point &pRef=cy1;
cout<<"\npRef as a point:"<<pRef;
Circle &cRef=cy1;
cout<<"\ncRef as a Circle:"<<cRef;
return 0;
}





[解决办法]
偶遇到类似问题都是用
“每次用/*...*/注释掉不同部分再重新编译，直到定位到具体语法出错的位置。”
的方法解决的。