Virtual functions are member functions whose behavior can be overridden in derived classes. As opposed to non-virtual functions, the overriding behavior is preserved even if there is no compile-time information about the actual type of the class. That is to say, if a derived class is handled using pointer or reference to the base class, a call to an overridden virtual function would invoke the behavior defined in the derived class. Such a function call is known as virtual function call or virtual call. Virtual function call is suppressed if the function is selected using qualified name lookup (that is, if the function's name appears to the right of the scope resolution operator ::).