Path: utzoo!attcan!uunet!husc6!rice!titan!phil
From: phil@titan.rice.edu (William LeFebvre)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computer reprogramming
Message-ID: <1972@kalliope.rice.edu>
Date: 6 Oct 88 16:20:00 GMT
References: <6689@nsc.nsc.com> <6980@ihlpl.ATT.COM> <1938@kalliope.rice.edu> <2993@jpl-devvax.JPL.NASA.GOV>
Sender: usenet@rice.edu
Reply-To: phil@Rice.edu (William LeFebvre)
Organization: Rice University, Houston
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In article <2993@jpl-devvax.JPL.NASA.GOV> leem@jplpro.JPL.NASA.GOV (Lee Mellinger) writes:
...
>HAL/S was written by Intermetrics, a company associated with MIT, and
>was named for the then head of the development Dr. Halcomb.  It is a
>high level realtime language based on PL/1.

Well, that ain't what I saw.  If that's the case, then I'm not sure what I
was looking at that day.  Except that it was somehow associated with the
on-flight software.

Unfortunately, I am not very familiar with the background of HAL/S (I only
know what I'm told).

>The computers are 4Pi/AP-101's which are esentially ruggedized IBM
>360's in a small box.  That is the four prime computers, the fifth is
>a Rockwell/Autonetics machine.

Wrong!  All FIVE general purpose computers (GPCs) are the same hardware.
They all sit on the same synchronized bus.  Hardware-wise, they are
totally identical.  It's the SOFTWARE that's different.  Four run the
standard flight software while the fifth runs the backup flight software
(the latter being written by Rockwell).  The backup software can be loaded
into any of the 5 GPCs, just as the main flight software can be loaded
into any of them.  Excuse me for being so adament about this, but this is
a common misconception.

			William LeFebvre
			Department of Computer Science
			Rice University
			<phil@Rice.edu>