pure virtual

Pure virtual is a term used in object-oriented programming that refers to a virtual function that is declared in a base class, but has no implementation or definition in the base class. Instead, the function is implemented in the derived classes that inherit from the base class.

A pure virtual function is declared in the base class using the syntax:

virtual return_type function_name(arguments) = 0;

The "= 0" at the end of the function declaration indicates that the function is pure virtual and has no implementation in the base class.

A class that contains one or more pure virtual functions is called an abstract class. An abstract class cannot be instantiated, meaning that you cannot create an object of that class. Instead, you must create an object of a derived class that implements the pure virtual functions.

The primary use of pure virtual functions is to create a common interface for a group of related classes that have different implementations of the same behavior. By defining a pure virtual function in a base class, you can ensure that all derived classes provide an implementation for that function. This allows you to write generic code that works with objects of any of the derived classes.