Short acronyms may be all upper case. All other letters are lower case. An exception is for identifiers matching a foreign language. In particular, we use all lower case where appropriate for C.
ALIword which stands for Ada Library Information and is by convention always written in upper-case when used in entity names.
Iis too easily confused with
1in some fonts. Similarly don’t use the variable
O, which is too easily mistaken for the number