What does “friend” mean in C++?

In C++, the keyword ‘friend’ is used to declare a function or class as a friend of another class. A friend function or class can directly access the private members of the class declared as a friend.

More specifically, when a function or class is declared as a friend of another class, it can access the private members of that class, including private member variables and functions. This allows specific functions or classes to have direct access to private members without needing to access them through the class’s public interface.

Using the ‘friend’ keyword can enhance the flexibility and efficiency of a program, but it may also compromise the principle of encapsulation, so it should be used cautiously.