What best defines 'data encapsulation' in programming?

Data encapsulation in programming is best defined as the technique of keeping data private and accessible only via methods. This concept is a fundamental principle of object-oriented programming (OOP). It allows a class to protect its internal state and manage its data securely, ensuring that other parts of the program cannot directly access or modify its internal data without proper interfaces—typically through getter and setter methods.

Encapsulation promotes modularity and reduces complexity by providing a clear separation between the object's internal representation and the external code that interacts with it. By controlling access to data and hiding implementation details, encapsulation improves code maintainability and reduces the risk of unintended side effects from changes in data structures or logic.

In contrast, the other options describe different concepts that do not align with the definition of data encapsulation. Splitting data files, converting data into encrypted formats, or merging data sources focus on different aspects of data handling and management rather than the protective and organizational features inherent in encapsulation.