A bit of computer history here! This is always fun.
Once upon a time, computers weren’t very interactive, but ran jobs one-at-a-time in batch mode only, or maybe not even batch mode – you had computer operators who manually loaded and ran each job one at a time. Input was typically from punched card decks, and output was typically to a lineprinter. Computers commonly had a single typewriter-like console for the operator.
Terminals in the modern sense appeared with the advent of time-sharing systems, which were a Big Deal in their early days, circa late 1960’s.
Teletype(r) terminals had long been standard in telegraph communications. A newsroom full of teletypes all going clackety-clackety-clack became an entrenched meme – For the last five thousand years, turn on any TV or radio news show and their opening theme music consisted of Teletypes going clackety-clack, which was later stylized as music with a Teletype-sounding percussion and beat – CBS news still has some vestiges of that.
Teletypes talked to one other remotely via wired connections – So they were an instant perfect fit, to become the standard devices for those new-fangled time-sharing computer systems with lots and lots of users scattered around the campus.
Photo of Teletype, from this article on computer history.
When I arrived at U. C. Berkeley in summer of 1969, the campus had rooms full of these terminals all over the place, even though the computer system they were attached to wasn’t even a time-sharing system. (Go figure.)
Very early in the 1970’s (say, around 1971 or so), we began to see “glass terminals” – these were computer monitors that basically emulated those Teletypes, but with a CRT screen. They had capabilities only just slightly more advanced than a Teletype. Wikipedia article on Computer Terminals with some pictures. In particular, these terminals typically did text-only, and no graphics. Some could do text in multiple colors; others were monochrome. Later on, some could do primitive graphics, and better graphics gradually evolved.
Throughout this period, these terminals weren’t actually part of the computer. They were external devices, connected through ports, which we now commonly call COM ports. Many many other kinds of devices could be attached similarly. Example: In modern supermarkets, take a look at the cash register. The receipt printer, electronic scale, scanner (sometimes several), PIN-pad, and various other devices are commonly connected via COM ports, even to this day.
With the advent of personal computers in the late 1970’s, the whole paradigm shifted. Now, instead of one massive mainframe computer, possibly with hundreds of time-sharing users, you now have more of a one-computer/one-person scheme. Now, each computer has its own monitor, which is still an external device, but connected through a more specialized monitor port. Note that the monitor and keyboard are typically no longer a single device as they used to be; now they are completely separate in a typical PC architecture.
IIRC, Apple came out with the Apple II circa 1978 or 1979, which was the first commercially successful PC. DIY hobbyists had been playing around with things like this for a few years before that in their garages, and computer research facilities like Stanford Research Institute (SRI) had been playing around with this stuff to, I think.
So I’m going to go with 1978 or 1979 as being the year when computer monitors, in the form most currently recognizable, hit the mainstream.
It’s still sending a form back to a mainframe, or at least something that is emulating one.