What is the main purpose of an abstract class in programming?

An abstract class serves as a blueprint for derived classes by providing a common interface and functionality that those classes can inherit and implement. It allows a programmer to define methods that must be created within any derived class, while also enabling them to provide shared functionality that can be utilized by all subclasses. This concept promotes code reusability and logical organization of code, helping to streamline the development process by ensuring that all derived classes maintain consistent behaviors.

Abstract classes often contain abstract methods (methods without implementations) as well as concrete methods (fully implemented methods). This setup allows derived classes to either override the abstract methods or use the existing implementation from the abstract class, defining a contract that all subclasses must follow.

This characteristic of serving as a template for creating a group of related classes distinguishes abstract classes from other types in programming. Choices that suggest instantiation of objects directly or defining only static methods do not align with the purpose of abstract classes, as they cannot be instantiated and typically include instance methods relevant for the subclasses that inherit from them.