[znpy]

I went and skimmed the rfc you're citing and it's fro 1988, it's old enough to have samples in C code where the "register" keyword is still used (afaik nowadays most compilers will ignore it) along with assembly code for motorola 68020, Cray CPUs and the IBM-370.

EDIT: for reference: https://datatracker.ietf.org/doc/html/rfc1071.html