Arizona State University (ASU) CSE240 Introduction to Programming Languages Midterm Practice Exam

The primary characteristic that distinguishes an abstract class from a regular class is that an abstract class cannot be instantiated and is intended for subclassing. This means that it serves as a blueprint for other classes, allowing those subclasses to inherit its properties and methods while providing a structure to ensure that certain functionalities are implemented in all derived classes.

Abstract classes can contain abstract methods—methods that are declared but not defined within the abstract class itself. Subclasses that derive from the abstract class must provide concrete implementations of these abstract methods. This enforces a certain design pattern and ensures that all subclasses provide necessary functionality, while still allowing for a common interface and shared code in the abstract class.

In contrast, a regular class can be instantiated directly and typically provides all the necessary functionality for its objects to be created and used. This key distinction underscores the role of abstract classes in object-oriented programming—they allow for flexibility and reuse of code while ensuring adherence to defined structures in subclasses.