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Apollo 11 Guidance Computer source code

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Re: Apollo 11 Guidance Computer source code

#141

Post by EvanAnderson »

It's interesting to me that the AGC contains an implementation of a virtual machine that is used to perform the higher-level mathematical functions (called 'The Interpreter'). Some details are available in this PDF starting on page 74: http://www.ibiblio.org/apollo/NARA-SW/E-2052.pdf

It would be fun to do some research into the embedding of higher-level virtual machines in earlier computers. I'm thinking of 'The Interpreter' in the AGC as being an ancestor to 'SWEET16' in the Apple II (https://en.wikipedia.org/wiki/SWEET16), or the 'Graphic Programming Language' (http://www.unige.ch/medecine/nouspikel/ti99/gpl.htm) in the TI-99/4A.

Re: Apollo 11 Guidance Computer source code

#142

Post by makinori »

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...

when bait clicking grammar infiltrates regular english grammar....

Re: Apollo 11 Guidance Computer source code

#143

Post by NEDM64 »

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)

Because writing control routines is not a big deal in assembly.

Specially in these CISC processors.

Re: Apollo 11 Guidance Computer source code

#144

Post by datenwolf »

mbrumlow wrote: post #134
datenwolf wrote: post #65

Earlier quoted context omitted.

> 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".

"The bulk of the software was on read-only rope memory and thus couldn't be changed in operation, but some key parts of the software were stored in standard read-write magnetic-core memory and could be overwritten by the astronauts using the DSKY interface, as was done on Apollo 14." Seams you were mostly right about not being able to change it. I was only somewhat right because I assumed it would all be editable. I…

> "The bulk of the software was on read-only rope memory and thus couldn't be changed in operation, but some key parts of the software were stored in standard read-write magnetic-core memory and could be overwritten by the astronauts using the DSKY interface, as was done on Apollo 14."

Ah, yes right, there was something. I've been fascinated by the AGC by some time¹, yet I completely forget about that. Time to hunt down the mission protocols to understand what this patch did.

------

1: … and the LVDC, which is the computer that controlled the Saturn-V. Because it was based on the computers used in ICBMs still a lot of information about that is classified. A lot of people conjectured that it was a IBM System 360 reshaped, but when actual LVDS board got torn down by electronics nerds over the past couple of years some significant differences to the 360 were discovered.

Re: Apollo 11 Guidance Computer source code

#145

Post by kamaal »

sizzzzlerz wrote: post #40
sixothree wrote: post #26

What was the development environment like for this code?

Pencil, eraser, paper, Punchcards, punchcard machine, Punchcard reader, computer, papertape, papertape puncher, AGC computer, Command Module, LEM, Neil Armstrong, Buzz Aldrin, Michael Collins. These last 3 are software QA.

When I worked on my start up, We built our complete hardware and then software for it.

I had to write down the drivers, and display library for the 128 x 64 lcd display with a simple scheduler, FSM and all!(Hard to mention all the work) Bulk of the work I did was using paper, eraser and pens.

A lot of work in unchartered territory requires paper work. I realized the more I worked on paper the more correct the code was and overall it took faster to write(given fewer bugs).

Re: Apollo 11 Guidance Computer source code

#146

Post by thevibesman »

Bromskloss wrote: post #127
pests wrote: post #123

Earlier quoted context omitted.

Remind your friend these comments are only left by a small vocal minority and is not representative of the project or its maintainers. This is akin to not liking something because you don't like the people who already like it, despite how much you'd like it otherwise.

Clue me in! What kind of comments are we talking about? Anything inappropriate here must have gone over my head.

The two aspects my friend's perception of the Rust community are both a) rewriting existing projects in Rust for the sake of having a version written in Rust[1][2], and b) it seems a frequent trend on Hacker News to see comments about "why didn't you write it in Rust" or "how about porting it to Rust" on posts about projects and "should have written it in Rust" comments on posts about security bugs. As the parent to your comment points out, this is probably a small group in the community who comments often.

As I could see from the way my score, on the post that started this discussion fluctuated, this is clearly a topic some are both sensitive about or like find humor in (or both!).

EDIT: I didn't mean to derail the discussion of a fascinating code posting; but I assume the comment I responded to that spawned this tangent, "Have they considered rewriting it in rust?"[3], was a joke made about the other comments on HN to rewrite things in Rust.

[1]: From a pedagogical standpoint, obviously this is a potentially good way of learning a language so if for learning and not pure calorie burn I personally don't see this as wasteful.

[2]: > I understand there is some motivations within (perhaps a small part) the Rust community to replace the world'S C-systems-code with more secure Rust code.

[3]: https://news.ycombinator.com/item?id=12049521

Re: Apollo 11 Guidance Computer source code

#147

Post by thevibesman »

pests wrote: post #123
thevibesman wrote: post #89

Earlier quoted context omitted.

hehe (A friend of mine, who when in search of a new go-to-programming language instead of Python, was more interested in Swift vs Rust because of this attitude).

Remind your friend these comments are only left by a small vocal minority and is not representative of the project or its maintainers. This is akin to not liking something because you don't like the people who already like it, despite how much you'd like it otherwise.

> Remind your friend these comments are only left by a small vocal minority and is not representative of the project or its maintainers.

Thanks for mentioning this, I certainly will the next time. The last time this came up, this was not an attitude I had previously noticed, although did see a bunch on Hacker News the following week

> This is akin to not liking something because you don't like the people who already like it, despite how much you'd like it otherwise.

I would totally agree with this, but at the same time, while not a technical reason, if one works in primarily a single programming language I can imagine the nature of the community would be a legitimate factor to consider---in this case though as you point out, it would be an inaccurate opinion of the nature of the Rust community.

Re: Apollo 11 Guidance Computer source code

#148

Post by jakub_h »

js2 wrote: post #133
blueintegral wrote: post #48

Someone opened an issue: "Check continuity on O2 cryogenic tanks before allowing stir" https://github.com/chrislgarry/Apollo-11/issues/3

This is a classic XY issue, suggesting a fix ("Check continuity...") instead of describing the problem ("O2 tanks exploded during Apollo 13 mission"). Further, I believe that the suggested fix is incorrect, or at least insufficient. The Apollo 13 investigation indicated that a list of factors led to the fan wires in the O2 tanks having damaged insulation. However, unless the wires were already short-circuited before…

Or maybe describing the problem in the explicit way you mentioned instead of the oblique way would have ruined the joke?

Re: Apollo 11 Guidance Computer source code

#150

Post by pests »

thevibesman wrote: post #147
pests wrote: post #123

Earlier quoted context omitted.

Remind your friend these comments are only left by a small vocal minority and is not representative of the project or its maintainers. This is akin to not liking something because you don't like the people who already like it, despite how much you'd like it otherwise.

> Remind your friend these comments are only left by a small vocal minority and is not representative of the project or its maintainers. Thanks for mentioning this, I certainly will the next time. The last time this came up, this was not an attitude I had previously noticed, although did see a bunch on Hacker News the following week > This is akin to not liking something because you don't like the people who already…

Sorry for the late reply.

To your last point, I agree slightly as well but my rebuttal would be that each person chooses how much and at what level to participate in a community they are in and which sub-communities they identify closer with.

I can imagine a person being proficient and working in any language without the need for them to be involved with the community at all, or if they do need to interact do so in a read-only matter.

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