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Apollo 11 Guidance Computer source code

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Re: Apollo 11 Guidance Computer source code

#61

Post by WhitneyLand »

In case you're wondering what hardware this source code is for: https://en.wikipedia.org/wiki/Apollo_Guidance_Computer

The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo Command Module (CM) and Lunar Module (LM). The AGC provided computation and electronic interfaces for guidance, navigation, and control of the spacecraft. The AGC had a 16-bit word length, with 15 data bits and one parity bit. Most of the software on the AGC was stored in a special read only memory known as core rope memory, fashioned by weaving wires through magnetic cores, though a small amount of read-write core memory was provided.

Re: Apollo 11 Guidance Computer source code

#62

Post by datenwolf »

emcrazyone wrote: post #55

I often wonder about the electronics of 1969 and what was done to mitigate radiation problems. For instance, the type of memory was called core rope memory https://en.wikipedia.org/wiki/Apollo_Guidance_Computer For anyone interested, XPrize winner Karsten Becker talks to popular youtube blogger David Jones about radiation, extreme heat & cold in space and specifically talks about bit flip and how electronic parts are…

> For instance, the type of memory was called core rope memory

Rope and core memory were the standard memory technologies of the day and very likely have not been chosed for they radiation hardness. The fact is, solid state memory became reliable and available in quantities only in the second half of the 1970-ies.

Re: Apollo 11 Guidance Computer source code

#63

Post by ceocoder »

phireal wrote: post #38
ceocoder wrote: post #31

Earlier quoted context omitted.

I really wish we can do an AMA with these two, > # THE MASTER IGNITION ROUTINE WAS CONCEIVED AND EXECUTED, AND (NOTA BENE) IS MAINTAINED BY ADLER AND EYLES. I had to look this up, NOTA BENE is latin for, observe carefully or take special notice

Hence N.B.

I never made that connection. TIL. Thank you!

Re: Apollo 11 Guidance Computer source code

#64

Post by lisper »

marxidad wrote: post #53
sjtgraham wrote: post #6

BURN_BABY_BURN--MASTER_IGNITION_ROUTINE.s - https://github.com/chrislgarry/Apollo-11/blob/dc4ea6735c4646...

I learned a new word: ULLAGE (the amount by which a container falls short of being full)

Ullage (the word) has terrestrial applications too:

https://en.wikipedia.org/wiki/Ullage_(wine)

Re: Apollo 11 Guidance Computer source code

#65

Post by datenwolf »

mbrumlow wrote: post #34
alehander42 wrote: post #20

people could've really used a higher-level language compiling to optimized AGC(apollo computer) assembly. Is there any reason why they didn't develop one? It seems it would've helped tremendously with the productivity and verification (and a lot of the explanations and equations would be readable as code, not as an non-executed comment)

I could be wrong. But I think part of why they did it this way was so they could edit things on the fly if a emergency dictated so. Having to ship a compiler (would have likely been an entire separate computer) would have not been feasible. With things done this way and documented this why they could (fairly sure did) have the pages printed out on paper and such. And if say there was some bug or new routine that need…

> I could be wrong. But I think part of why they did it this way was so they could edit things on the fly

The AGC code was stored in ROM. Notably a specific kind of ROM called "rope memory".

Re: Apollo 11 Guidance Computer source code

#67

Post by waiseristy »

victorantos wrote: post #28
js2 wrote: post #21

Watch the landing: https://www.youtube.com/watch?v=k_OD2V6fMLQ During the landing, you'll here mention of 1201 and 1202 alarms. Here's what that's about: http://www.hq.nasa.gov/office/pao/History/alsj/a11/a11.1201-... Here's 1201 being called: https://github.com/chrislgarry/Apollo-11/blob/dc4ea6735c4646... And 1202: https://github.com/chrislgarry/Apollo-11/blob/dc4ea6735c4646...

This one is better image quality https://www.youtube.com/watch?v=Jg80HZsv_js

Here's one with subtitles and interactivity http://www.firstmenonthemoon.com/

Re: Apollo 11 Guidance Computer source code

#68

Post by AstroJetson »

dandrews wrote: post #49
alehander42 wrote: post #20

people could've really used a higher-level language compiling to optimized AGC(apollo computer) assembly. Is there any reason why they didn't develop one? It seems it would've helped tremendously with the productivity and verification (and a lot of the explanations and equations would be readable as code, not as an non-executed comment)

It was pretty much taken as gospel everywhere at the time that NO compiler could match the speed and size of a well crafted assembly language routine. Back then there were some noble attempts at building optimizing compilers, and probably the more notable one was IBM's ambitious ForTran H. But that's 50-year-old tech now, kids. Remember also that memory was at a terrific premium. I don't have any specific knowledge a…

This sounds interesting, any link to a second source on this?

Re: Apollo 11 Guidance Computer source code

#69

Post by nerdy »

How about the code apparently marked for deletion? https://github.com/chrislgarry/Apollo-11/blob/dc4ea6735c4646...

I've often wondered many things about the cleanliness, maintainability and style of such code (this particular system, in fact). It's fun to be able to actually poke through it.

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