Re: status of PL/I as a viable language

[Richard Riehle <richard@adaworks.com>]

"Donald L. Dobbs" wrote:

> Richard Riehle wrote:
> > "Donald L. Dobbs" wrote:
>
> >>PS: ADA ain't that great.  Even with the Pentagon's (DoD) legislative
> >>fiat they couldn't achieve widespread adoption.  It proved to be far too
> >>clunky for its original intent which was embedded real-time applications
> >>such as radar and fire-control systems.  Over time ADA will join Pascal
> >>as one of the wannabes that just didn't have enduring traction.
> >
> >
> > Actually, Ada is that great ...
> >
> >
> > It is used (I know this from first hand experience) very successfully
> > in a large number of embedded weapon systems, embedded avionics,
> > embedded commercial systems.   It flies airplanes (all the software
> > in the Boeing 777), drives communication satellites,  controls electrical
> > power plants (including nuclear),  and keeps ships active at sea.  It
> > is the primary language of the F-22, among others.
>
> Not to belabor a point, but one of the lead stories today on the
> Aviation Week web site www.aviationnow.com describes how the F-22
> program is now some $800 million overrun because of delays caused by
> unreliable software.  They can get it to run for about 8 hrs in the lab
> before it crashes, but in the actual test flights it fails within 3.5
> hours forcing the pilot to reboot the system while in mid-flight.  If
> they are using Ada as you contend, then this is a terrible indictment
> and confirms what I had heard earlier about the language's shortcomings.

Donald,

I will cross-post this to comp.lang.ada.

The F-22 is one of the most complex systems, software and
hardware, even conceived.   As we discussed earlier, with
regard to other language environments,  the quality of the
available tools can help only so much.

Ada is designed to maximize the amount of error checking possible
as early in the development process as possible.  I know of no other language
does this as well as Ada.    As stated earlier, competent people have used
Ada for a wide variety of successful large-scale, safety-critical software
systems.  On the other hand, less competent people have used Ada, PL/I,
C++, C, etc. for a wide variety of unsuccessful systems.   At least one
Ada failure that I know of by reports from participants rather than from
first-hand knowledge was an Air Traffic Control system.   The people
who were managing the system blamed Ada when they, the managers,
were the real problem.   At that time, other ATC systems had already
been completed in Ada and were successfully doing their job.   The
problem is not the language.  As someone else once said, "A fool
with a tool is still a fool."    From my vantage point, having a fairly
broad experience with a lot of programming languages, Ada, once it
is understood, continues to be the most appropriate choice for systems
such as the F-22.   The fact that developers can find a way to screw it
up does not detract from the value of the language.   If they can make
a mess using a language with the rigorous controls built into Ada,
imagine the magnitude of the mess they could make with, say, C++.
And, no, PL/I would not help with a system this large and complex.

Richard Riehle