#include<iostream.h>
#include<conio.h>
class shape
{protected:double d1,d2;
 public:virtual void displayarea()=0;
	void getdata()
	{cout<<"\n enter the parameters for area to be calculated:";
	 cout<<"\n enter length: ";
	 cin>>d1;
	 cout<<"\n enter width or height: ";
	 cin>>d2;
	}
};
class triangle:public shape
{public:void displayarea()
	{cout<<"\n the area of triangle is:"<<d1*d2/2;
	}
}t;
class rectangle:public shape
{public:void displayarea()
	{cout<<"\n the area of rectangle is:"<<d1*d2;
	}
}r;

void main()
{int n=0,i;
 shape *ptr;
  clrscr();
 while(n!=1)
 {clrscr();
  cout<<"\n enter the choice of figure whose area is to be calculated \n1-rectangle\n2-triangle\n3-exit\nenter your choice:";
  cin>>i;
  switch(i)
  {case 1:cout<<"\nfor rectangle\n";
	  ptr=&r;
	  ptr->getdata();
	  ptr->displayarea();
	  break;
   case 2:cout<<"\nfor triangle\n";
	  ptr=&t;
	  ptr->getdata();
	  ptr->displayarea();
	  break;
   case 3:n=1;
	  break;
   default:cout<<"\n sorry you have entered wrong choice\n";
  }
  cout<<"\n do you want to continue (yes:0,no:1):";
  cin>>n;
 }
 getch();
}