1-A program in C++ using classes to calculate the area of a circle , a rectangle and a triangle on user’s choice.

#include<iostream.h>

#include<conio.h>

class ar

{private:float a;

 public:ar()

            {a=0;}

            ~ar()

            {a=0;}

            void area(float x)

            {a=3.4142*x*x;

            }

            void area(float x,float y)

            {a=x*y;

            }

            void area(float x,float y,int u)

            {a=(x*y)/2;

            }

            void showarea()

            {cout<<"\n the area of the figure is:"<<a;

            }

}n1;

void main()

{int n=0,i;

 float h,b,r;

 clrscr();

 while(n!=1)

 {clrscr();

  cout<<"\n enter the choice of figure whose area is to be calculated \n1-circle\n2-rectangle\n3-triangle\nenter your choice:";

  cin>>i;

  switch(i)

  {case 1:cout<<"\nfor circle\n";

              cout<<"\n enter the radius of the circle:";

              cin>>r;

              n1.area(r);

              n1.showarea();

              break;

   case 2:cout<<"\nfor rectangle\n";

              cout<<"\n enter the  length of the rectangle:";

              cin>>h;

              cout<<"\n enter the width of the rectangel:";

              cin>>b;

              n1.area(h,b);

              n1.showarea();

              break;

   case 3:cout<<"\nfor triangle\n";

              cout<<"\n enter the  height of the triangle:";

              cin>>h;

              cout<<"\n enter the base length of the triangel:";

              cin>>b;

              n1.area(h,b,1);

              n1.showarea();

              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();

}