ESR performs a useful service in pulling together a document on what all hackers used to need to know, regardless of the particular technical interest they followed. I was never technical enough to be a hacker, but I worked with many of them, so I had to know (or know where to find) much of this information, too.
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 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 directly useful today – until you trip over some piece of still-functioning technology where it’s relevant (like a GPS puck), or it makes sense of some old-fart war story. Even so, it’s good to know anyway, for cultural-literacy reasons.
One thing this collection has that tends to be indefinite in the minds of older hackers is calendar dates. Those of us who lived through all this tend to have remembered order and dependencies but not exact timing; here, I did the research to pin a lot of that down. I’ve noticed that people have a tendency to retrospectively back-date the technologies that interest them, so even if you did live through the era it describes you might get a few surprises from reading.
There are references to Unix in here because I am mainly attempting to educate younger open-source hackers working on Unix-derived systems such as Linux and the BSDs. If those terms mean nothing to you, the rest of this document probably won’t either.