C++ interface vs abstract class

To be an abstract class, it must have a presence of at least one virtual class . We can use pointers and references to abstract class types. If we don’t override the virtual function in the derived class, then the derived class also becomes an abstract class. We can create constructors of an abstract class.

An abstract class is a class that is designed to be specifically used as a base class . An abstract class contains at least one pure virtual function. You declare a pure virtual function by using a pure specifier ( = 0 ) in the declaration of a virtual member function in the class declaration.

The purpose of an abstract class is to define a common protocol for a set of concrete subclasses . This is useful when defining objects that share code, abstract ideas, etc. Attempts to instantiate an abstract class will always result in a compiler error.

No, They are not obsolete . In fact, there is an obscure but fundamental difference between Abstract Classes/Methods and Interfaces. if the set of classes in which one of these has to be used have a common behaviour that they share (related classes, i mean), then go for Abstract classes/methods.