In programming, what is an identifier that does not change called?

In programming, a constant is an identifier that represents a value that cannot be altered once it has been assigned. This characteristic distinguishes constants from variables, which can change during program execution.

Constants are used to hold fixed values that are not meant to change throughout the course of the program, which can help prevent accidental modification of critical data. For instance, values representing mathematical constants like pi or the speed of light are typically defined as constants. Defining values as constants can lead to easier maintenance and better readability of the code, as it becomes clear to other programmers that these values should not be altered.

Recognizing the role of constants is essential for writing robust code, especially in cases where certain values are fundamental to the logic of the program. In contrast, variables and other options provided can change and thus do not serve the purpose of representing fixed values.