You can inherit a base class privately by leaving off the public in the base-class list, or by explicitly saying private (probably a better policy because it is clear to the user that you mean it). When you inherit privately, you’re “implementing in terms of;” that is, you’re creating a new class that has all of the data and functionality of the base class, but that functionality is hidden, so it’s only part of the underlying implementation. The class user has no access to the underlying functionality, and an object cannot be treated as a instance of the base class (as it was in FName2.cpp).

You may wonder what the purpose of private inheritance is, because the alternative of using composition to create a private object in the new class seems more appropriate. private inheritance is included in the language for completeness, but if for no other reason than to reduce confusion, you’ll usually want to use composition rather than private inheritance. However, there may occasionally be situations where you want to produce part of the same interface as the base class and disallow the treatment of the object as if it were a base-class object. private inheritance provides this ability.