Apollo 11 Guidance Computer source code for the command and lunar modules • Hacker News Board

Re: Apollo 11 Guidance Computer source code for the command and lunar modules

#31

Post by wopian » Thu, Feb 20, 2020, 1:39 AM UTC

thewonderidiot wrote: post #20

ryanmarsh wrote: post #12

Earlier quoted context omitted.

>NUMERO MYSTERIOSO https://github.com/chrislgarry/Apollo-11/blob/master/Luminar...

People frequently seem to think this is about the line number it's on (666), but that doesn't have anything to do with it. That line number is a totally modern construction; the original source code was on punch cards. That particular comment was punched onto card number 0562 in the LUNAR LANDING GUIDANCE EQUATIONS log section. The original developers only referred to code by punch card number, and page number in the…

It should be 1. "GAINBRAK,1" is assigning 1 to GAINBRAK.

Re: Apollo 11 Guidance Computer source code for the command and lunar modules

#32

Post by ASalazarMX » Thu, Feb 20, 2020, 2:31 AM UTC

davidw wrote: post #26

ASalazarMX wrote: post #25

Earlier quoted context omitted.

The whole line is not as shocking # BURN, BABY, BURN -- MASTER IGNITION ROUTINE

It makes sense in context, of course, I just didn't think of NASA in the late 60ies as the sort of place where you could write 'clever' things like that.

Back when AS/400s were AS/400s, I made a little tool to help the operators run a long process at night. I felt playful and left an easter egg: on Fridays the 13th, it would work as usual, but display a skull and bones with blinking red eyes while doing it.

It seems that Fridays the 13th are rarer than I estimated, because months later my boss woke me up at midnight because the operators had woken her up because it was the first time the egg was triggered. In hindsight, it was a foolish thing to add since this was a bank. Fortunately they took it with good humor, and even kept the easter egg to scare new people.

I suppose NASA is more formal than a bank, so they only let you fool around with the comments.

Re: Apollo 11 Guidance Computer source code for the command and lunar modules

#33

Post by thewonderidiot » Thu, Feb 20, 2020, 3:21 AM UTC

wopian wrote: post #31

thewonderidiot wrote: post #20

Earlier quoted context omitted.

People frequently seem to think this is about the line number it's on (666), but that doesn't have anything to do with it. That line number is a totally modern construction; the original source code was on punch cards. That particular comment was punched onto card number 0562 in the LUNAR LANDING GUIDANCE EQUATIONS log section. The original developers only referred to code by punch card number, and page number in the…

It should be 1. "GAINBRAK,1" is assigning 1 to GAINBRAK.

No, it's not. The 1 here is using interpretive index register X1 to index onto GAINBRAK. The star on the DMP means that multiplication is indexed. GAINBRAK is one of the pad-loaded descent targeting parameters; the index selects the appropriate number based on the phase of the descent.