Re: Multiple reasons for failure of Ariane 5 (was: Re: Ariane 5 - not an exception?)

[Dave Jones <djones@starbase.neosoft.com>]

Ken,

On Mon, 26 Aug 1996, Ken Garlington wrote:

> 
> How's that list of real-time flight systems written in PL/I progressing?
>
   
    It's not a flight system, of course (unless you count the times I've
loaded up my P/390 box on an airliner and used it for work...:-)), but
my company has been quite successful in using PL/I to develop and
market a line of VM/ESA performance monitor analysis and reporting tools.
The data capture part *has* to be able to respond within a fixed amount
of time whenever CP has more monitor data to be processed (and if it
isn't, it's overwritten by the next interval's data), and it can't hog
the entire CPU doing it, either. Most sites don't want to see their
performance monitor as one of the top consumers of cycles....:-) We use
PL/I as the primary development language and we've had a very good track
record in the market. It provides all of the tools we need to be able
to capture the data, reduce it to a manageable subset (a lot of floating
point work here), and output to files for further analysis *very quickly*.

  Many VM sites use the data in the CP monitor for a wide variety of
tasks and cannot afford to lose even a very small amount of it do to
any failures in the data collect and reporting systems. PL/I provides us
with the necessary features to make our software robust and fail-soft;
when things do get out of hand, we're able to note what the problem is,
(and, in many cases, gracefully recover from it), alert the operators,
and continue in some manner. To our customers, taking a CP dump and 
terminating is simply unacceptable. 

   Does, this mean that PL/I is "better than" Ada, or C, or Fortran, or
....? No, of course not, it just means that when used in an appropreate
manner in an environment it was designed for, it's a very good choice
for a serious development language. We'd gain nothing by switching
languages for this kind of work in this type of environment. I think that
this is also true of a large number of other sites that currently use PL/I
now as  well. 

Dave Jones
Velocity Software
Houston, TX 
 
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