What is the concept and purpose of C++ virtual functions?

A virtual function in C++ is a function declared in a base class that can be overridden in a derived class. Virtual functions are declared using the keyword “virtual” and allow for a generic function interface to be defined in the base class, with specific implementations being overridden in the derived classes according to their individual requirements.

The main purpose of virtual functions is to implement polymorphism. Polymorphism is an important concept in object-oriented programming where the appropriate function is executed at runtime based on the actual type of the object. By pointing a base class pointer or reference to a derived class object and calling a virtual function, function calls can be dynamically bound based on the actual type of the object.

The purpose of virtual functions also includes implementing dynamic binding of functions, supporting calls to derived class objects through base class pointers or references, and enabling runtime type identification (RTTI).

It is important to note that using virtual functions will result in some runtime overhead because the function call needs to be dynamically determined at runtime. Therefore, when designing class inheritance relationships, it is necessary to consider specific needs and performance factors to decide whether or not to use virtual functions.