Re: JOB:Sr. SW Engineers Wanted-Fortune 500 Co

["Mike Silva" <mjsilva@jps.net>]

Since nobody else has answered your question I didn't want to let it go
without a try.  The general approach, whether via built-in or hand-coded
exception handling, is to try to continue to supply best-guess results.  If
you think of a given chunk of software as a black box with some input, some
output, and a red "Exception!" light on it, the idea is that when the red
light goes on you try to stick something useful in the output even if you
don't know where in the box the problem lies.  This something useful could
be predetermined data, or previous-pass data, or perhaps data from another
process which is good enough to limp along on.  Or perhaps you switch to
another mode which doesn't require the output of the failed "box".  At the
same time you can try to re-initialize any hardware associated with the box
(e.g. I've seen LCD displays that sometimes go out to lunch and need to be
coaxed back into a working electrical state via re-initialization).  The
possibilities are endless, depending on the hardware and the software
functional breakdown, but quite often you can think of something useful to
do, especially in the short term (in the case that the hardware just had a
momentary hiccup).

To extend the safety belt analogy, you add collapsible steering columns and
safety glass windows even though the safety belt will never allow you to hit
the wheel or the windows.

Mike

Hyman Rosen wrote in message ...
>kilgallen@eisner.decus.org (Larry Kilgallen) writes:
>> And some small fraction of automobile collision victims who are not
wearing
>> safety belts are "thrown clear".  Exceptional cases do get more press.
>
>I am clearly in need of enlightenment, so please explain to me. After
>you have decided that a given situation is impossible, will you
>nevertheless add an error handler for that impossible situation, so
>that if it happens anyway, you can recover gracefully? To what level
>of detail and impossibility will you go? When you write Ada code, how
>many exception handlers for Program Error do you put into your code?