What was the first computer to have interactive text on a CRT ?

  • That the text on screen responded to key-presses without significant delay .

I remember seeing some very early radar-installation CRT's that seemed to display numbers or text, however, I don't know if this equipment was computers (by definition), although they may have been .

The earliest I have found is the following - Early PDP-1

  • 3
    The question combines somewhat unrelated requirements. Interactive is a feature of a computer, not a display, similar receiving a key press/toggle. Further is text content thus not really technology related or does it matter if the text is displayed by vextors or pixels? So the question comes rather down to asking for a CRT based display that could be updated from a computer.
    – Raffzahn
    Commented Jul 2, 2019 at 20:13
  • My 1st computer after Univ. EE'75 was a HP9825 80 column calculator with smart HP CRT then two end to end with a rack of HP-IB instruments in "my world" 's 1st SCADA system for Black Brandt ground remote control of all payload instruments prior to launch for remote places like Churchhill or others without two 50 wire umbilicals a mile between launch & remote control building. Commented Jul 3, 2019 at 2:48

2 Answers 2


Prior to DEC's PDP-1, of 1959, there would be MIT's TX-2 of 1958 - after all, the PDP-1 (and DEC itself), was a spin off of this project (and team). That said, it was only a single machine and a research project, not anything commercial available.

Before that, there was the SAGE system, operational in 1958, which was used for RADAR surveillance. Images from this system are maybe what you had in mind. The displays were completely synthetic (computer-generated) on hardware made by IBM based on the 740/780 linage.

Thus I'd say, an IBM 740 system, and here especially the IBM 780 CRT Display, qualifies as first. Likewise in display capabilities, as well as being commercial available since 1954. Connected to a 701 (or similar machine), interactive computer displays could be generated.

That is, of course, not counting the Williams Tube used by the 701 itself - and before that with the Manchester Baby, in 1948 (and Mark 1 in 1949). Both, without a doubt, could be used to display patterns including characters. And for sure it was a direct reaction :)

... I guess that's as far as the 'first' stuff can go in this context :))

  • This page suggests that Williams tubes were intended to be used as display, not just storage, in the 1949 EDSAC at Cambridge: "It was not till around October 1949 that it was fully operational, with paper tape input-output,... it was available for general use for other departments and Ferranti from April 1949, without paper tape input-output (you still had to key into store in binary, and read output from CRT displays in binary). curation.cs.manchester.ac.uk/computer50/www.computer50.org/…
    – Owain
    Commented Jul 2, 2019 at 20:54
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    @Owain Well, calling it 'intended' is a bit, well stretched. That was more of a hack to test the machine during build, using the side effect of Williams tubes. For a display it would have been more than a magnitude less expensive to use conventional tubes. Also, isn't that the whole for the paragraph?
    – Raffzahn
    Commented Jul 2, 2019 at 21:10
  • When I came to MIT in 1971 I begged and was allowed to use the TX-0. It took up a large room, and had a human mediated startup checklist because the power supplies used mercury vapor rectifier, and the various supplies needed to be sequenced. Once everything was powered up, I pressed one little button to make the first timing pulse, and it was off. I programmed a pen follower to track the light pen -- a peripheral not seen much these days.
    – cmm
    Commented Jul 3, 2019 at 18:10
  • The radar-installation CRT's I mentioned in the question seemed to be much earlier than the SAGE system, I have only seen footage of them once or twice. A possible explanation of what I saw - I have now found that they used to place transparencies over the screens for various purposes, which contained professionally printed alphanumeric-characters etc, and I'm guessing maybe they were printed in some sort of phosphorous or other ink that would glow when it was hit by the electron-beam . Commented Jul 30, 2019 at 1:19
  • @questiontype: From what I've read, some RADAR displays had two sets of deflection controls, so that the beam would first pass through a selectable aperture within a plate and then from there be aimed at the proper position on the screen. Never seen such a thing in operation, and I don't know if any such devices are still functional.
    – supercat
    Commented Jul 30, 2019 at 2:42

Since the 'Manchester Baby' is mentioned above, I thought I might mention this one, since it's very interesting, for those who may accept game-sprite like objects instead of text, although I don't.

The MIDSAC computer computer had a billiards game in 1954, very impressive .

  • Wow.... a mere 65 years ago. Mind boggling! This doesn't answer the question, but then I do wonder if @questiontype was anticipating that interactive text would have come before graphics?
    – Matt Lacey
    Commented Aug 6, 2019 at 12:43

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