How does a variable differ from a constant in programming?

In programming, the key distinction between a variable and a constant lies in their behavior regarding value changes. A variable is designed to hold data that can be modified throughout the execution of a program. This means that the value stored in a variable can be reassigned or updated as needed based on the program's logic or user input. On the other hand, a constant is explicitly defined to hold a value that cannot be altered once it has been assigned. This fixed nature of constants is crucial for ensuring that certain values remain unchanged during the program’s execution, providing stability and predictability in calculations or conditions.

The other options do not accurately represent the fundamental characteristics of variables and constants. For example, a variable does not have to be written in uppercase or lowercase specifically. The casing of variable names is determined by the naming conventions of the programming language in use rather than the inherent properties of variables themselves. Additionally, a distinction based solely on what they hold—references for variables and values for constants—does not universally apply across all programming languages. Thus, the correct answer emphasizes the capacity for change, which fundamentally differentiates variables from constants in programming contexts.