FAQ 18.02 How are private: , protected: , and public: different?

FAQ 18.02 How are private:, protected:, and public: different?

The situation is similar to personal secrets (shared only with friends), family secrets (shared with friends and children), and nonsecrets (shared with anybody), respectively.

A private: member of a class is accessible only by members and friends of the class.

A protected: member of a class is accessible by members and friends of the class and by members and friends of derived classes, provided they access the base member via a pointer or a reference to their own derived class.

A public: member of a class is accessible by everyone.

There is no difference between the access rules for data members and member functions. "Members and friends of class X" include member functions of class X, friend functions of class X, and member functions of friend classes of class X.