I'd say, "Congratulations! You're one of today's luck 10,000!", but trigraphs aren't really much fun. Just another reminder that C is old, and computing is even older.
I've used uppercase-only terminals, and I've used ancient C, but not at the same time.
I thought ISO added them when C went from ANSI C (1989) to ISO C (1990), along with wchar.h and such. I might misremember, though, it's been a long time since I did anything serious with C.
Come to think of it, didn't they remove trigraphs in one of the more recent iterations of the standard?
They did remove trigraphs in one of the more recent iterations. It's possible that it was as you say, but I have this vague memory that it was ANSI who added them. I think maybe what the ISO added were https://en.wikipedia.org/wiki/C_alternative_tokens.
I've used uppercase-only terminals, and I've used ancient C, but not at the same time.