Overload a function area.

//Program to overload a function area.
#include<iostream.h>
#include<conio.h>
#include<math.h>

void area(float);
void area(float,float);
void area(float,float,float);

void main()
{
    clrscr();
    int a;
    cout<<"Choose: "<<endl<<"1.Area of circle."<<endl<<"2.Area of rectangle"<<endl<<"3.Area of triangle: "<<endl;
    cin>>a;
    switch(a) {
    case 1: cout<<"Enter radius: "<<endl;
        int r;
        cin>>r;
        area(r);
        break;

    case 2: cout<<"Enter length and width: "<<endl;
        int l,w;
        cin>>l>>w;
        area(l,w);
        break;

    case 3: cout<<"Enter the lengths of 3 sides of triangle: "<<endl;
        int b,c,d;
        cin>>b>>c>>d;
        area(b,c,d);
        break;
    }
    getch();
}

void area(float r)
{
    float area=3.14*r*r;
    cout<<"The area of circle of radius "<<r<<" is: "<<area;
}
void area(float l, float w)
{
    float area=l*w;
    cout<<"The are of rectangle of length "<<l<<" and width "<<w<<" is: "<<area;
}
void area(float b, float c, float d)
{
    float s=(b+c+d)/2;
    float area=sqrt(s*(s-b)*(s-c)*(s-d));
    cout<<"The area of triangle is: "<<area;
}