I spent a lot of time in my early career on Allen-Bradley PLC 3's & 5's. They were definitely computers - no screens, and obviously purpose built for process control.
But then I started thinking... the HP 2100's that are the focus of my collecting, very often (usually, actually) didn't have system consoles. They were used primarily for test & measurement. And this wasn't just the earliest models; I acquired quite a few later full rack (21MX/E) systems that did not have a console board in them. They were booted via switch register settings and set about their task. Various changes to operation were made strictly via switch register. Then I recalled one of the early Educational BASIC HP systems (No, not TSB). It accepted BASIC programs from punched cards *only*. Output was to the printer. I can't recall what it was. I believe it used a TTY for initial configuration, but not thereafter. In any case... early computers without screens weren't necessarily so "early" in the scheme of things, and often did process control and test & measurement :) J
