Area Of Circle using Friend Function - C++Program

Definition Friend Function

If a function is friend function of a class, that friend function is not the actual member of the class.But which function has rights to access to all private and protected members (variables and functions).

For Better Understanding,

• Understanding Friend Function and Characteristics In C++
• Simple Program for Friend Function Using C++ Programming
• Introduction Of Classes ( OOPS )

Area Of Circle Definition

The area of a circle is π (Pi) times the Radius squared, which is written A=πr2.

The area of a circle is written
A=?r2

here,

r = Radius
? = ~3.14

Simple Program for Friend Function

// Area Of Circle using Friend Function - C++Program 
// GCC Compiler 

#include<iostream>

class AreaOfCircle {
    int radius;
public:
    void get() {
        std::cout << "Enter the radius of Circle : ";
        std::cin >> radius;
    }
    friend float calculate(AreaOfCircle ob);
};

float calculate(AreaOfCircle ob) {
    return 3.14 * ob.radius * ob.radius;
}

int main() {
    AreaOfCircle object;
    object.get();
    std::cout<<"\nArea of Circle : "<<calculate(object);
}

Sample Output

Enter the radius of Circle : 5                                                                                                         
                                                                                                                                       
Area of Circle : 78.5