Solutions to Saturday Mac riddles 26

I hope that you enjoyed Saturday’s Mac Riddles, episode 26. Here are my solutions to them.

1: Time Machine
Unlike the TARDIS (Doctor Who’s Time And Relative Dimension In Space system, a fictional time machine), I can take you back but not forward (TM can’t of course show files in the future, more’s the pity). What am I?

2: UUID (Universally Unique Identifier)
I’m by far the largest number you’ll commonly encounter (each is a 128-bit number), as I get everywhere now (used in almost every part of macOS). But you’ll be lucky to find out who I represent (there’s no central registry of UUIDs, making it almost impossible to discover what each represents). Who am I?

3: A developer’s keyboard has the 9 and 0 keys, in the top row of numbers, worn out. Which language do they use? Answer: Lisp, typically Common Lisp.
Those are the keys used (with Shift) for parentheses (), which are the commonest structural feature of the language. For example, to add two numbers:
(let ((a 10)
(b 4))
(+ a b))

that’s 10 parentheses for a single operator. Indeed, Lisp has been sarcastically referred to as being formed from Lots of Idiotic and Spurious Parentheses, or similar. It is, in reality, a wonderful language which was supported in classic Mac days by Macintosh Common Lisp.

I look forward to your putting alternative cases.