A class whose primary purpose is to define an interface. An abstract class defers some or all of its implementation to subclasses. An abstract class cannot be instantiated.
Given a class A that maintains a reference to an abstract class B, class A is said to be abstractly coupled to B. We call this abstract coupling because A refers to a type of object, not a concrete object.
An operation that declares a signature but doesn’t implement it. In C++, an abstract operation corresponds to a pure virtual member function.
A class that refers to another class has an acquaintance with that class.
An object that’s composed of subobjects. The subobjects ...