What does encapsulation refer to in object-oriented programming?

Encapsulation in object-oriented programming refers to the concept of bundling data and the methods that operate on that data within a single unit, typically a class. This principle allows for data hiding, whereby the internal state of an object is protected from unintended interference and misuse by outside code. By controlling access to an object's data through public methods (or interfaces), encapsulation promotes a clear separation between the object's internal representation and its external interaction. Thus, this helps maintain integrity and enhances modularity, since changes to an object's implementation do not affect other parts of the program that rely on the object's interface.

The other options touch on related concepts in programming but do not accurately define encapsulation. For instance, while the separation of code and data is a part of structuring programs effectively, it does not capture the essence of encapsulation. Similarly, implementing public and private methods relates to access control within a class but doesn't embrace the broader aspect of data and behavior organization that encapsulation represents. Inheritance is a separate principle that deals with the creation of new classes based on existing ones, which is not the focus when discussing encapsulation.