What is an abstract class in C ++?

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.

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Is abstract class useless?

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.

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