Stage 1.4: Changing Variables

Rust cares a great deal about what variables are modifiable. Values fall into two types:

• mutable - the compiler will allow the variable to be written to and read from.
• immutable - the compiler will only allow the variable to be read from.

Mutable values are denoted with a mut keyword.

We will have more to say on this concept later, but for now just keep an eye out for this keyword.