How to find Area of Circle and Diameter in C++.

Program:
#include <iostream>
#include <conio>
void main()
{
float area, radius, circumference;
int choice;
cout<<"Enter radius: "<<endl;
cin>>radius;
cout<<"Enter 1 for area and 2 for circumference "<<endl;
cin>>choice;
if(choice==1)
{
area=radius*radius*3.14;
cout<<"Area = "<<area<<endl;
}
else if(choice==2)
{
circumference=2.0*3.141*radius;
cout<<"Circumference = "<<circumference<<endl;
}
else
cout<<"Invalid choice"<<endl;
getch();
}

Output Result: