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From: l107353@cliffy.lfwc.lockheed.com (Garlington KE)
Newsgroups: comp.lang.ada
Subject: Re: "Subtract C, add Ada"
Date: 20 Jan 1995 22:07:47 GMT
Organization: Lockheed Fort Worth Company
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 <3fng3t$2ak@Starbase.NeoSoft.COM>
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Date: 1995-01-20T22:07:47+00:00
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Samuel Mize (smize@Starbase.NeoSoft.COM) wrote:
: Sure you do, if there was a programmer error, or a hardware glitch,
: or a bad memory location, etc.  These are the things you don't want.
: Given that you can't eliminate those, oh *boy* do you want exceptions,
: given the alternative (core dump at 30,000 feet -- how do I reboot
: my F-16?!?!?!?)

Actually, as one of the software engineers who developed the F-16 digital
flight control system (as well as the YF-22A flight control system), I can
say with confidence that you _don't_ want exceptions for a human programmer
error, since no one has figured out an adequate response to them in a 
dynamic feedback system like a flight control system. It doesn't matter what
happens in the other cases since there is physical redundancy and output
monitoring as a part of the total system.

However, for systems with the capability to degrade cleanly, exceptions are
a very good thing and in fact are widely used in embedded avionics software.

--------------------------------------------------------------------
Ken Garlington                  GarlingtonKE@lfwc.lockheed.com
F-22 Computer Resources         Lockheed Fort Worth Co.

If LFWC or the F-22 program has any opinions, they aren't telling me.