Path: utzoo!attcan!uunet!husc6!bbn!inmet!ishmael!inmet!authorplaceholder
From: fosler@inmet.UUCP
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computer reprogramming
Message-ID: <146300001@inmet>
Date: 17 Oct 88 23:04:00 GMT
References: <6689@nsc.nsc.com>
Lines: 26
Nf-ID: #R:nsc.nsc.com:6689:inmet:146300001:000:1518
Nf-From: inmet.UUCP!fosler    Oct 17 19:04:00 1988


    HAL/S was developed by Intermetrics, Inc. for NASA starting in 1970.
The prototype language, HAL, was implelemented in 1971, and was used
successfully to verify early shuttle software design concepts and algorithms.
The new verion, HAL/S, was define in 1972, with the first compiler for
the IBM 360/370 in 1973, and the onboard Shuttle computer (IBM Ap-101) in
1974.  (Taken from the foreword to "Programming in HAL/S").

    While I have never work on the HAL/S compiler, it was told to me that
the compiler maintenance had been moved from the Cambridge office to the
Houston, Texas office four or five years ago.  At that time, the Houston
office was working on improving the optimization of the code generated,
and modifing the compiler to support more memory (to work with the new
computers that had more memory).  I can not remember what had to be
changed to support the increased memory, but I do know from working on
a similar computer for the NAVY that the IBM instructions and bus structure
puts limits on the total amount of memory that the computer can work with.
The new IBM computers might have more memory, but more then likely, NASA
will have to come up with a new computer if they want the computer support
more then several megabytes of memory.
   I also know from the NAVY project that I have work with, that project hate
to recompile any code for any reason.  They have found that they can get
around all of the retesting of their code if they just make patches.

Carl Fosler
Intermetrics, Inc.