Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!ucbvax!hplabs!hpda!hpcupt1!stachnik
From: stachnik@hpcupt1.cup.hp.com (George Stachnik)
Newsgroups: comp.sys.hp
Subject: Re: HP3000/9xx Software Wanted
Message-ID: <67870035@hpcupt1.cup.hp.com>
Date: 12 Jun 91 18:10:51 GMT
References: <1991Jun4.213903.24875@ncsu.edu>
Organization: Hewlett Packard, Cupertino
Lines: 19

/ hpcupt1:comp.sys.hp / knechod%peruvian.utah.edu@cs.utah.edu (Kevin Nechodom) /  7:46 am  Jun 11, 1991 /
>
>Usually on MPE, OS changes never cause (correct) working programs to fail.
>Some customers have programs > 10 years old that continue to work.
>(but anything can happen, and does.  :-)

>From this, I conclude:  a) HP does an excellent job of maintaining
>compatibility, unless b) you are running at the limits of your stack space.
I'd concur with the opinion that most MPE applications survive ordinary 
O/S updates with no problems.  Most MPE customers have come to expect that.
This is due in part to the nature of the O/S (a very robust and stable set of
APIs) and due in part to the nature of the applications, which are written
with the objective of having a long "shelf life" - [not always the case with
unix applications IMHO.

Also, the stack overflow problems that were common on MPE V machines have 
all but vanished with MPE XL.  The native mode stack on XL is HUGE compared
to the relatively tiny 64k stack permitted on MPE V.  So it's harder to 
overflow.  It can be done, but it takes a pretty determined effort. :^).