What are the characteristics of C++ virtual functions?

Characteristics of C++ virtual functions include:

1. Polymorphism: Virtual functions allow calling methods of derived classes through a base class pointer or reference, achieving polymorphism.
2. Dynamic binding: the call to a virtual function is bound at runtime based on the actual type of the object, rather than at compile-time.
3. Inheritance: Virtual functions are defined in the base class and can be overridden by derived classes. The virtual functions in a derived class have the same name and parameter list as those in the base class, but they can have different implementations.
4. Virtual function table: For each class in C++ that contains virtual functions, the compiler generates a virtual function table (vtable), which stores the addresses of the virtual functions. When a virtual function is called through an object of the class, the compiler searches for the corresponding function address in the vtable.
5. Default implementation: A virtual function can have a default implementation, which can be used by derived classes when they do not need to override the virtual function.
6. Pure virtual function: a virtual function can be declared as a pure virtual function, which means it has no implementation and derived classes must provide their own. Classes with pure virtual functions are called abstract classes, and cannot be instantiated, only used as base classes.