by Eric S. Raymond <esr@thyrsus.com> One fine day in January 2017 I was reminded of something I had half-noticed a few times over the previous decade. That is, younger hackers don’t know the bit structure of ASCII and the meaning of the odder control characters in it. This is knowledge every fledgling hacker used to absorb through their pores. It’s nobody’s fault this changed; the obsolescence of hardware terminals and the near-obsolescence of the RS-232 protocol is what did it. Tools generate culture; sometimes, when a tool becomes obsolete, a bit of cultural commonality quietly evaporates. It can be difficult to notice that this has happened. This document is a collection of facts about ASCII and related technologies, notably hardware terminals and RS-232 and modems. This is lore that was at one time near-universal and is no longer. It’s not likely to be dire...