Which of the following correctly defines a 'constant' in programming?

A constant in programming is defined as a value that does not change during program execution. This means that once a constant is assigned a value at the beginning, that value remains fixed throughout the life of the program. Constants are often used to represent fixed values that hold significance, such as mathematical constants (like Pi) or configuration values, ensuring that they are not inadvertently modified later in the code, which helps maintain the integrity and readability of the program.

While variables are designed to allow changes to values during execution, a constant prevents this, lending reliability and stability to programs. This differentiation is crucial in programming, where the intention of the code often revolves around whether values should remain static or be mutable.

The other options do not accurately capture the definition of a constant: variable mutation, datatype restrictions, or temporary storage do not embody the primary characteristic of immutability that constants are known for.