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From: "jtarver" <jtarver@tminet.com>
Subject: Re: [Fwd: F22 completes 11% of its Flight tests]
Date: 2000/01/12
Message-ID: <jW3f4.2191$iy5.112956@typ12.deja.bcandid.com>#1/1
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 <387CC1C0.4C57E34C@quadruscorp.com>
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Newsgroups: comp.lang.ada,rec.aviation.military
Date: 2000-01-12T00:00:00+00:00
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Marin D. Condic <mcondic-nospam@quadruscorp.com> wrote in message
news:387CC1C0.4C57E34C@quadruscorp.com...
> >
> > It will be highly impressive to see a version of Ada that is actually
> > transportable.  The first thing the development of Ada compilers did was
> > allow extensions in direct violation of the charter for the system.
This
> > worked to deliver the pork to Boston, but really comprimised the intent
of
> > the DARPA program funding Ada.
> >
> > John
>
> I worked F22 engine control software written in Ada for years - and may
> yet again someday. We were having a similar problem with respect to the
> M68040 becoming obsolete and needing to be replaced (probably by the
> PowerPC) as the engine goes into production. I'll throw my $0.02 worth
> in:
>
> There is not now, nor has there ever been, *any* computer language that
> is 100% portable. *Especially* in the field of embedded computers. So
> when portability comes up, you have to ask the question as a matter of
> degree.

"It all depends", as they say.

> Ada is the most portable language I have ever worked with. I have
> dragged large chunks of Ada code out of an embedded environment and
> compiled it with zero modifications on a Sun workstation and on a PC and
> had it run just as it did in the embedded box. I have had very similar
> experiences with a large number of other bodies of code (non-embedded)
> so I don't think this was unique.

Ada was originally envisioned to be platform transparent.  When Data General
produced the only 100% compliant compliler and the Ada development program
went for the noncompliant VAX as their standard platform that idea was out
the window.

> The trick with programming long lived embedded computers is knowing how
> to isolate the things which are going to be processor/system specific.
> That way, when you have to upgrade to new hardware, the problem isn't as
> horrific. The biggest problem is that changing anything in the box means
> you have to go through huge amounts of revalidation of the system, and
> this is an issue independent of the processor or language you choose to
> use. Ada has always been a big help in enhancing portability, but it can
> never solve all of the problems. No language can.

Well you know I'd like to argue with you, but there is little in what you
wrote to dispute.

John