Friend Functions

A – What Is a Friend Function?

A friend function is a function that is not part of a class, but it is given special access to the class’s private and protected members. Normally, only class methods can access private variables. But a friend function breaks that rule because the class trusts it.

To declare a function as a friend, you use the keyword friend inside the class declaration.

This is useful in cases like:

• Overloading operators (like << for printing)

• Helper functions that need access to private values

• Comparing or combining two different classes

Even though the function is defined outside the class, it can "see" the class's private variables.

B – Declaring and Using a Friend Function

Let’s say we have a class called Box, and we want a function called printBox to print the width, which is private.