“The DSKY and PINBALL (something flashy with buttons) was a demo.
And that demo got us to the moon.
"Apparently, nobody had yet arrived at any kind of software requirements for the AGC's user interface when the desire arose within the Instrumentation Laboratory to set up a demo guidance-computer unit with which to impress visitors to the lab. Of course, this demo would have to do something, if it was going to be at all impressive, and to do something it would need some software. In short order, some of the coders threw together a demo program, inventing and using the verb/noun user-interface concept, but without any idea that the verb/noun concept would somehow survive into the flight software. As time passed, and more and more people became familiar with the demo, nobody got around to inventing an improvement for the user interface, so the coders simply built it into the flight software without any specific requirements to do so."
For anyone interested in the process of compiling and loading the code for these systems (available at https://github.com/chrislgarry/Apollo-11/ ) into the "core rope memory" used for program storage in the capsules, here's one of the original spec documents, as well as an image from that document showing what I'd call a "compilation-bureaucracy-pipeline" that's a fascinating glimpse into software deployment practices.
Wikipedia says there were visible-light LEDs in 1962 (https://en.wikipedia.org/wiki/Light-emitting_diode#Discoveri...), but even ignoring they emitted red light, which the photos do not show, I think it’s unlikely they used them in this device.
https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#DSKY_... claims it used ”green high-voltage electroluminescent seven-segment displays”. That seems more likely to me.
Fran Blanche attempted a GoFundMe project to recreate these displays. Unfortunately the project stalled.
* The Apollo Guidance Computer: Architecture and Operation - Frank O'Brien
* Digital Apollo: Human and Machine in Spaceflight - David A. Mindell
"How Apollo Flew to the Moon" by W David Woods
First episode: https://www.youtube.com/watch?v=2KSahAoOLdU
It describes that not just DELTAH was killed due to overload, but that whole system restarted (and reloaded critical landing tasks that were restart-protected)