Don't remember where I read that, but supposedly by the type C and UNIX were being made, they had upgraded to Model 38 teletypes, which do have a way to type "all 128 ASCII characters" according to the manual
Notice the positions of [] and {}, that seems inconvenient to me, but maybe it's just because of habit...
@vaporeon_ 6 significant initial characters for external identifiers as of ANSI C (case sensitivity not required)! 31 and case sensitivity for internal identifiers, including macro names.
@vaporeon_ notionally, at least. probably in practice many actual implementations guaranteed more than that but i have no idea.
C99 increased it to 31 for external identifiers (63 for internal) and i think guaranteed case sensitivity, so you don't need super recent to have it guaranteed (and probably most or all implementations had less constrained limits by then anyway)
@alyssa I somehow wasn't aware that ANSI C still had this limitation... So if I'm writing a library in C (targeting older systems that do not have any newer versions of C), I should make sure that every external symbol has distinct 6 characters at the start?