What is a constant in programming?

A constant in programming is a named value that cannot be altered during program execution. This means that once a constant is defined and given a specific value, that value remains fixed throughout the program's execution. Constants are used for values that should not change, providing clarity and reducing the risk of accidental modification of important data. For instance, if you set the value of Pi (π) as a constant, you can rely on it being the same throughout your calculations, ensuring consistency and accuracy in mathematical operations.

In contrast, a value that can change during program execution refers to variables, which are used to hold data that needs to be modified. Feedback loops relate to a process in programming where the output is fed back into the system, typically in iterative algorithms, and do not define constants. A variable that stores user input, while it may behave similarly to constants in terms of name referencing, is designed specifically to hold data that is subject to change based on user actions. Thus, option B accurately describes the unique property of constants within programming.