[OT] We Choose The Moon

[Ben Scott]

On Thu, Jul 23, 2009 at 7:34 AM, Jon 'maddog' Hall<maddog at li.org> wrote:
> I am downloading a PDF of the AGC program "Luminary" ... the program
> used on the Lunar Lander is also there ...

  LUMINARY is the main program for the LM (Lunar Modular, the lander).
 The main program for the CM (Command Module, the cone-shaped thing
that was the only part to return to Earth) was COLOSSUS.  (I don't
believe Dr. Forbin was involved.)

  Both the CM and the CM had an AGC (Apollo Guidance Computer), which
today we probably call CPU, RAM, and ROM.

  The ROM was "rope memory".  It contained all the software, and was
"woven" *by hand*.  It took several months to manufacture, so code
freeze had to take place well in advance of launch.  Not exactly the
rapid code-debug-modify cycle of today.

  The RAM was 2 Ki (2048) words.  Each word was 16 bits -- 15 data
bits plus a parity bit.  16 KiB in today's nomenclature.  The ROM was
36 Ki words (36,864 KiB today).

  There was also a DSKY (display and keyboard) unit to provide user
interface.  The CM had two DSKYs; the LM had one.  The DSKY was
technically an independent computer (albeit one with a fixed and very
limited program).  The AGCs communicated with the DSKYs over
communication lines.  (Predecessor to the X Window System, perhaps?
;-)  )

  When the LM was docked, the CM could use either AGC.  The intent was
for the LM AGC to provide a backup in the event  of CM AGC failure.

  During independent flight, the LM didn't have that option, so it had
a separate computer, the "Abort Guidance System".  It was
independently manufactured and programmed.  It only had enough
capability to get the LM back into orbit -- it couldn't land, but if
it turned out MIT totally screwed the pooch with the LM systems, it
would keep the astronauts alive.

http://history.nasa.gov/computers/Ch2-5.html

http://history.nasa.gov/computers/Ch2-6.html

  You can get full emulators of the AGC and DSKY on-line, if you want
to try your hand as an Apollo computer programmer.  You don't even
need to make your own rope memory.

http://www.ibiblio.org/apollo/

  Yes, I'm a space junkie!  :-D

-- Ben