Re: [Fwd: F22 completes 11% of its Flight tests]

["Marin D. Condic" <mcondic-nospam@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.

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.

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.

MDC
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