Today if you are a Linux user and fire up a terminal window to “do something” at the command-line, you are using a gooey program to emulate an old terminal which was separate to the computer.
Today you are almost always using a keyboard and screen connected directly to the computer you are using and the gooey program you fire up as a terminal is in fact originally called a terminal emulator. That is, it pretends to be a real terminal.
So what were these real terminals?
The earliest “terminals” were actually teletypes for communicating text messages over long distances (over wires!). Not only was there no digital computer involved, but they predate computers by quite a way – the earliest ones were used in the late 19th century. And of course printed the text onto paper directly. The earliest digital computers used these teletypes as input and output devices, so you could type in commands and see the result immediately (or as quickly as the result could be produced). These early days still leave some traces today :-
✓ mike@Lime» tty /dev/pts/5
The “tty” command commemorates those old printing terminals – the “tt” in “tty” is short for “teletype”.
The speed and wasted paper of those printing terminals was a bit tedious, so the 1970s saw them gradually replaced with glass teletypes – which were basically keyboards and CRT screens built into an enclosure that would attach to a central computer over a serial line.
These terminals (and showing an ADM 3A here is a little unfair as it wasn’t quite this simple) were really simple – they had exactly the same capabilities as the printing terminals. No cursor control (meaning no full screen editing), plain text, no italics or bold, etc.
Over time, more and more features were added to the terminal allowing more usable software (in particular the learning curve was not quite as steep). These features grew to accommodate colour, graphics, the ability to load and save data locally, and even the ability to function as a microcomputer (the HP pictured below could run CP/M in certain configurations).
But where did they go?
The heyday of the terminal was in the 1980s when many office-based companies were busy trying to put something like a computer on every desk, and a terminal connected to a central computer was one way of doing that. But they compared rather poorly with microcomputers – typically very slow in comparison, less likely to offer any kind of graphics (graphics was an option but typically cost as much as a microcomputer), and just wasn’t very “cool”.
Despite several attempts at resurrecting them (they were popular amongst those who had to centrally support them), they never really returned.
But they do survive inside modern operating systems in terms of a terminal emulator (as mentioned previously) to access the operating system command line – all three main operating systems (Windows, macOS, and Linux) have a terminal emulator of sorts. And Microsoft is actually investing in re-engineering their terminal emulator.