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Source code for the Apollo 11 Guidance Computer

ibiblio.org

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Re: Source code for the Apollo 11 Guidance Computer

#61

Post by raldi »

dang wrote: post #55

The source code is here: http://www.ibiblio.org/apollo/listings/Comanche055/ . We changed the url to the top-level page which provides an overview. Edit: see subthread below.

Hmm.

To me, the appeal of the original link was that, with one click, I could see the entire annotated-with-original-comments source of any part of the AGC. That was really exciting. A simulator (to me at least) is a lot less interesting ... and it's certainly an objectively very different kind of thing. (I for one wouldn't have even bothered clicking the current headline if I hadn't been looking for the original post's comments, which I had seen earlier.)

I'm not against curation in general -- it's a crucial aspect of HN, perhaps the crucial aspect. But I do think this particular case was a bit odd.

Re: Source code for the Apollo 11 Guidance Computer

#62

Post by hcrisp »

RogerL wrote: post #57
hcrisp wrote: post #52

Earlier quoted context omitted.

Wasn't it the PGNCS that had the Kalman filter? See my comment nearby which confused it with AGC.

It is my understanding that the AGC is the computer within the PGNCS. Terminology varies, as the last link below from NASA notes. So far as I can tell, the AGC maintained the state vectors for the KF. Ground control would run batch mode least squares solutions, and pass it on to the LM, where the updates to the state vector would be applied by hand. I freely admit to not having worked through the code, but I believe…

Thanks, that helps. I've always wondered what the variables of the state vector were -- position, velocity, etc. it appears from the link that it could be a 6x6 of those two (position, velocity in x, y, and z), or a 9x9 when including radar/landmark bias. Now I know!

Re: Source code for the Apollo 11 Guidance Computer

#63

Post by dang »

raldi wrote: post #61
dang wrote: post #55

The source code is here: http://www.ibiblio.org/apollo/listings/Comanche055/ . We changed the url to the top-level page which provides an overview. Edit: see subthread below.

Hmm. To me, the appeal of the original link was that, with one click, I could see the entire annotated-with-original-comments source of any part of the AGC. That was really exciting. A simulator (to me at least) is a lot less interesting ... and it's certainly an objectively very different kind of thing. (I for one wouldn't have even bothered clicking the current headline if I hadn't been looking for the original pos…

Ok, that's pretty persuasive, especially since most of the comments here are about the code. We changed it back.

Re: Source code for the Apollo 11 Guidance Computer

#64

Post by joezydeco »

egoebelbecker wrote: post #9
spain wrote: post #8

http://www.ibiblio.org/apollo/listings/Comanche055/PINBALL_G... >Filename: PINBALL_GAME_BUTTONS_AND_LIGHTS.agc Can someone explain what this is? I doubt they had an actual game of pinball in their guidance computer.

It appears to be the code for the controls: # THE KEYBOARD AND DISPLAY SYSTEM PROGRAM OPERATES UNDER EXECUTIVE # CONTROL AND PROCESSES INFORMATION EXCHANGED BETWEEN THE AGC AND THE # COMPUTER OPERATOR. THE INPUTS TO THE PROGRAM ARE FROM THE KEYBOARD, # FROM INTERNAL PROGRAM, AND FROM THE UPLINK. I think it's just someone with a sense of humor.

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."[1]

[1] http://www.ibiblio.org/apollo/ForDummies.html

Re: Source code for the Apollo 11 Guidance Computer

#66

Post by thret »

nsxwolf wrote: post #34

Do the famous 1201 and 1202 error codes make an appearance here? My assembly skills aren't good enough to find them, I'm afraid.

# Page 1220

# IDLING AND COMPUTER ACTIVITY (GREEN) LIGHT MAINTENANCE. THE IDLING ROUTIEN IS NOT A JOB IN ITSELF,

# BUT RATHER A SUBROUTINE OF THE EXECUTIVE.

I'm cursed to see spelling errors immediately, and obvious bugs only after hours of frustration.

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