Here's an example. Hypothetically say you want to build an HTML parser.
You might encounter tags like <html>, <HTML>, <Html>, etc., but you want to perform a hash table lookup.
So first you're going to normalize to either lower- or uppercase.
You might encounter tags like <html>, <HTML>, <Html>, etc., but you want to perform a hash table lookup.
So first you're going to normalize to either lower- or uppercase.
And to GP, SGML/HTML actually has a facility to define uppercasing rules beyond ASCII, namely the LCNMSTRT, UCNMSTRT, LCNMCHAR, UCNMCHAR options in the SYNTAX NAMING section in the SGML declaration introduced in the "Extended Naming Rules" revision of ISO 8879 (SGML std, cf. https://sgmljs.net/docs/sgmlrefman.html). Like basically everything else on this level, these rules are still used by HTML 5 to this date, and in particular, that while elements names can contain arbitrary characters, only those in the IRV (ASCII) get case-folded for canonization.
ANSI C was designed to be written by humans using a plain text editor. That doesn't make it a human language.