About friend function in c++.

Friend function

• Friend function declaration can appear anywhere in the class.
• But a good practice would be where the class ends.
• An ordinary function that is not the member function of a class has no privilege to access the private data members, but the friend function does have the capability to access any private data members.
• The declaration of the friend function is very simple.
• The keyword friend in the class prototype inside the class definition precedes it.
• Example to Demonstrate working of friend Function

/* C++ program to demonstrate the working of friend function.*/#include <iostream>
using namespace std; 

class Distance {
    private:
        int meter; 
    public:
        Distance(): meter(0){ }
        friend int func(Distance); //friend function 
};

int func(Distance d){
    //function definition
    d.meter=10; //accessing private data from non-member function
    return d.meter; 
}

int main(){ Distance D;
    cout<<"Distace: "<<func(D);
    system("pause"); 
    return 0;
}