What does encapsulation in object-oriented programming refer to?

Encapsulation in object-oriented programming is primarily about the bundling of data with the methods that operate on that data. This principle helps to restrict direct access to some of an object's components, which is essential for maintaining the integrity of the data. By combining both data and behavior into a single unit (known as an object), encapsulation allows an object to expose only what is necessary through a well-defined interface while hiding its internal workings.

This promotes a separation between the object's interface and its implementation, helping to reduce complexity and increase modularity in code. It allows for a clear distinction between what an object does (its behavior) and how it accomplishes that (its internal state), leading to cleaner and more maintainable code.

Other options do not accurately define encapsulation. The separation of code and data into different files pertains more to file organization and structure rather than encapsulation. Writing code without reusing existing code goes against the principles of efficiency and maintainability in programming and does not relate to encapsulation. Lastly, organizing data within databases refers to data management, which is distinct from the concept of encapsulation in the context of object-oriented programming.