The ability to change, in [[C++]], by default *all* variables are immutable. Many modern languages (eg. [[Rust]], modern JS/TS practices, [[Kotlin]]), will either make immutable variables the *default*, or have a modern convention of preferring [[#Immutability|immutable]] local variables if their mutability is not required. This is all just to say that the idea of preferring immutability is in no way a [[C++]] specific concept. >[!warning] local Immutable State is the Devil ## Immutability To make any value mutable, you can use a form of the [[Const]] keyword.