What best describes a Prototype in programming?

A prototype in programming is best described as a test model of a program. This means it serves as an initial version or mock-up that allows developers to explore ideas, test functionalities, and refine user interfaces before the final product is developed. Prototypes are designed to be iterated upon, helping to identify potential problems and gather feedback early in the development process. This approach enables teams to assess features and usability without committing to the full development of the complete software, thereby saving time and resources.

In contrast, the other options represent different stages or concepts in software development. A final version of the program refers to the completed software ready for distribution, while a stable release implies that the software has been tested thoroughly and deemed reliable for use by end-users. A user-defined variable pertains to the programming concept of allowing programmers to create their own variables rather than serving as a model for design or evaluation. These distinctions highlight the unique role of a prototype in the development lifecycle.