I'm not an expert on English, but I'm fairly picky. I'm also a programmer, and I regularly use the word "Id" as an abbreviation for Identifier. So I was wondering whether it's more correct to use "Id" or "ID". Maybe it's a meaningless question because as far as I know it's a unique usage of abbreviations as it's pronounced "eye-dee", but it does get on my OCD not knowing.
Edit: This question is about which is correct in the English language- the fact that it's for use in programming is incidental.