program to display a menu regarding rectangle

#include<iostream.h>
#include<conio.h>
#include<process.h>
#include<math.h>
int main()
{
clrscr();
char ch,ch1;
float l,b,peri,area,diag;
cout<<"\nRectangle menu";
cout<<"\n 1.area";
cout<<"\n 2.perimeter";
cout<<"\n 3.diagonal";
cout<<"\n 4.exit"<<"\n";
cout<<"enter your choice:";
do
{
cin>>ch;
if(ch=='1'|| ch=='2'||ch=='3')
{ cout<<"enter length & breadth:";
cin>>l>>b;
}
switch(ch)
{ case '1': area = l*b;
    cout<<"area="<<area;
    break ;
  case '2': peri = 2*(l+b);
    cout<<"perimeter="<<peri;
    break ;
  case '3': diag =((l*l)+(b*b));
    cout<<"diagnol="<<diag;
    break ;
  case '4': cout<<"breaking";
    exit(0);
  default : cout<<"wrog choice!!!!";
    cout<<"enter a valid one";
    break;
  } // end of switch.
  cout<<"\n want to enter more(y/n)?";
  cin>>ch1;
  if(ch1=='y'|| ch1=='y')
   cout<<"again enter your choice(1-4):";
   } while(ch1=='y'||ch1=='y'); //end of do-while loop
   return (0);
}