What programming concept allows the use of new classes based on existing classes?

The concept that allows the creation of new classes based on existing classes is inheritance. In object-oriented programming, inheritance enables a new class, often referred to as the subclass or derived class, to inherit properties and behaviors (methods) from an existing class, known as the superclass or base class. This fosters code reuse, as the subclass can leverage the functionality of the superclass while also introducing additional attributes or methods specific to itself.

Inheritance represents a hierarchical relationship between classes, allowing for the extension of existing functionality without rewriting code. This leads to a more organized and efficient codebase, where common functionality is encapsulated in the superclass, and specific functionality is implemented in the subclass. This distinction is crucial for building scalable applications and maintaining clean code.

In contrast, encapsulation refers to the bundling of data and methods that operate on that data within a single unit or class, while abstraction involves simplifying complex systems by modeling classes based on their essential characteristics, keeping unnecessary details hidden. Polymorphism allows objects of different classes to be treated as objects of a common superclass, enabling methods to operate on objects of various types through a common interface. Each of these concepts plays a significant role in object-oriented programming, but inheritance specifically addresses the creation of new classes from existing ones.