Scoping -- explicit
class B : public A {\fbox{}
public: virtual void operator()() { cout << "B"; cout << "B"; A::operator()(); } }; // A* a = new B(); a->A::operator()(); (*a)(); // produces: ABBA
class B : public A {\fbox{}
public: virtual void operator()() { cout << "B"; cout << "B"; A::operator()(); } }; // A* a = new B(); a->A::operator()(); (*a)(); // produces: ABBA