What is a fixed value that cannot be altered during the execution of a program?

A fixed value that cannot be altered during the execution of a program is referred to as a constant. Constants are used to represent values that remain the same throughout the run of a program. By declaring a constant, the programmer conveys the intent that this particular value should not change, which adds clarity to the code and helps prevent accidental modifications.

Constants are beneficial in many programming scenarios—for example, representing mathematical values like π or configuration settings that should remain unchanged. The use of constants can also enhance the readability of the code since it allows developers to replace literal values with meaningful names.

On the other hand, variables are meant to hold values that can change during program execution. Functions encapsulate blocks of code that perform specific tasks, while arrays represent collections of elements. These concepts are versatile and subject to modification, unlike constants, which are designated to be static throughout the program's lifecycle.