temporary variable: A variable used to store an intermediate value in a complex calculation.
dead code: Part of a program that can never be executed, often because it appears after a return statement.
None: A special value returned by functions that have no return statement or a return statement without an argument.
incremental development: A program development plan intended to avoid debugging by adding and testing only a small amount of code at a time.
scaffolding: Code that is used during program development but is not part of the ﬁnal version.
guardian: A programming pattern that uses a conditional statement to check for and handle circumstances that might cause an error.