What is a sub-program that returns a value known as?

A sub-program that returns a value is known as a function. Functions are designed to perform a specific task or calculation and send back a result to the part of the code that called them. In programming, a function takes input values (known as parameters), processes them, and then produces an output (the return value). This characteristic distinguishes functions from procedures, which typically perform actions but do not return a value.

Understanding the role of functions is crucial as they promote code reusability, reduce redundancy, and help in breaking complex problems into smaller, more manageable parts. Functions encapsulate logic and can simplify debugging and testing, making them a fundamental concept in many programming languages.