🟣 OOP · Lesson 44

Friend Function and Friend Class

What is Friend Function and Friend Class?

Friend Function and Friend Class
A friend function or class can access private and protected members of another class. It should be used carefully because it reduces strict encapsulation.

Level
🟣 Object-Oriented Programming

Example File
friend-functions.cpp

Main Focus
Concept + syntax + practical C++ program

Why should you learn this?

It helps you write correct and readable C++ programs.
It is used repeatedly in school practicals, projects and competitive programming.
It builds the base for advanced topics such as OOP, STL and data structures.

Important Terms

Term	Meaning / Use
friend	Friend Function and Friend Class programming में Friend use होता है।
private access	Friend Function and Friend Class programming में Private access use होता है।
non-member function	Non-Friend Function and Friend Class programming में member function use होता है।
controlled access	Friend Function and Friend Class programming में Controlled access use होता है।

Syntax / Pattern

C++

friend return_type functionName(ClassName obj);

Example Program

main.cpp

#include <iostream>
using namespace std;
class Box{
    int length = 10;
    friend void show(Box b);
};
void show(Box b){ cout << b.length; }
int main(){ Box b; show(b); }

Expected Output

Program Explanation

show() is not a member function.
Because it is friend, it can access private length.

Exam Tip: In C++ practical answers, write the logic first, then the program, then expected output. For theory, always include one suitable example.

Where will you use it?

operator overloading
closely related classes
utility functions

Common Mistakes

Using friend everywhere.
Thinking friend is inherited automatically.

Practice Tasks

Create friend function to add private values of two objects.
Explain why friend should be limited.

Summary

Friend Function and Friend Class एक ज़रूरी C++ topic है। परिभाषा सीखें, syntax समझें, example program चलाएं और फिर practice tasks हल करके concept मज़बूत करें।