Which term would best describe a system that prevents external alteration?

The term that best describes a system that prevents external alteration is encapsulation. Encapsulation is a fundamental principle in object-oriented programming that involves bundling the data (attributes) and the methods (functions) that operate on that data into a single unit, or class. By doing this, encapsulation restricts direct access to some of an object's components, which means that the internal representation of an object is hidden from the outside. This prevents external code from making arbitrary changes to the inner workings of the object, ensuring that the object's state cannot be altered unexpectedly or incorrectly.

This concept not only protects the integrity of the data but also allows for a clear interface for others interacting with the object, promoting better software design and maintainability. Encapsulation thus provides a way to enforce rules about how data can be accessed and modified, making it a key feature for creating robust and secure applications.

Inheritance relates to creating new classes from existing ones, allowing for shared attributes and methods, but doesn’t inherently protect data. Polymorphism allows methods to do different things based on the object that it is acting upon, illustrating flexibility rather than protection. Overloading involves defining multiple functions with the same name but different parameters, which is more about function versatility rather than safeguarding against alterations.