program of class to calculate area

#include<iostream.h>
#include<conio.h>
class area
{
public:
float r;
area(float a)
{
r=a;
}
void cal()
{
float a=3.14*r*r;
cout<<"area is"<<a;
}
};
void main()
{
clrscr();
float r;
cout<<"enter the value of radius\n";
cin>>r;
area A(r);
A.cal();
getch();
}