c++--Pure virtual function

A pure virtual function is a virtual member function that is marked as not specifically implemented.

It is used in situations where a base class is defined and the implementation of a virtual function in a base class cannot be defined, and its implementations depend on different derived classes.

The general format for defining pure virtual functions is:

Virtual return type function name (parameter table) = 0;

A base class that contains pure virtual functions cannot be used to define objects. A pure virtual function does not have an implementation part and cannot produce an object, so a class containing a pure virtual function is an abstract class.

c++--Pure virtual function