The Apollo 11 Lunar Module’s BAILOUT Code

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Wed Dec 25 2019 09:44:59 GMT+0000 (Coordinated Universal Time)

Saved by @albertthechecksum #historicalcode #nasa #apollo

POODOO    INHINT
    CA  Q
    TS  ALMCADR

    TC  BANKCALL
    CADR  VAC5STOR  # STORE ERASABLES FOR DEBUGGING PURPOSES.

    INDEX  ALMCADR
    CAF  0
ABORT2    TC  BORTENT

OCT77770  OCT  77770    # DONT MOVE
    CA  V37FLBIT  # IS AVERAGE G ON
    MASK  FLAGWRD7
    CCS  A
    TC  WHIMPER -1  # YES.  DONT DO POODOO.  DO BAILOUT.

    TC  DOWNFLAG
    ADRES  STATEFLG

    TC  DOWNFLAG
    ADRES  REINTFLG

    TC  DOWNFLAG
    ADRES  NODOFLAG

    TC  BANKCALL
    CADR  MR.KLEAN
    TC  WHIMPER
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1969: When the computer was at risk of running out of space (or “overflow”), the Apollo Guidance Computer triggered BAILOUT to schedule less important data and operations so it could keep the vital ones up and running. As the Eagle lander descended toward the moon’s surface, at 30,000 feet the AGC flashed a “1202” alarm, which neither Neil Armstrong nor the flight controller in Houston immediately recognized. But in less than 30 seconds, the computer experts in Mission Control relayed that the AGC software was doing just what it was supposed to: drop lower-priority work and restart the important jobs (so quickly that it was imperceptible to the crew). Armstrong and Buzz Aldrin would continue to get what they absolutely needed from the AGC to keep on the path to touchdown. Overflow alarms would sound three more times before Armstrong uttered “the Eagle has landed,” but always because things worked as intended. The word “bailout” normally signals the failed end of a mission, but here it helped make humanity’s highest achievement a reality. —Ellen Stofan, John and Adrienne Mars Director, Smithsonian’s National Air and Space Museum

https://slate.com/technology/2019/10/consequential-computer-code-software-history.html