Message-related functions.
- $Aborted — return value for aborted evaluations
- Check — discard the result if the evaluation produced messages
- $Failed — retrieved result for failed evaluations
- Failure — a failure at the level of the interpreter
- General — general-purpose messages
- Message — display a message
- MessageName — associate a message name with a tag
- Off — turn off a message for printing
- On — turn on a message for printing
- Quiet — evaluate without showing messages
- Syntax — syntax messages