Which term defines the act of having a variable that cannot be changed once it is set?

Which term defines the act of having a variable that cannot be changed once it is set?

• A. Index
• B. Instance
• C. Instantiation
• D. Immutability

Answer: (D)

Immutability is the property that a value cannot be changed after it is created. When something is immutable, any operation that seems to modify it actually yields a new value, leaving the original unchanged. This concept helps with predictability and thread safety, and you’ll see it in practice with constants or read-only values in many languages. The other terms describe different ideas: an index is a position in a collection, an instance is a concrete object from a class, and instantiation is the process of creating that object. They don’t capture the idea of a value that cannot be altered after being set, which is exactly what immutability conveys.

Immutability is the property that a value cannot be changed after it is created. When something is immutable, any operation that seems to modify it actually yields a new value, leaving the original unchanged. This concept helps with predictability and thread safety, and you’ll see it in practice with constants or read-only values in many languages. The other terms describe different ideas: an index is a position in a collection, an instance is a concrete object from a class, and instantiation is the process of creating that object. They don’t capture the idea of a value that cannot be altered after being set, which is exactly what immutability conveys.