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From: esf00@amdahl.amdahl.com (Elliott S. Frank)
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Was the 360 badly-designed?  (was Re: Compatibility with EBCDIC)
Message-ID: <12956@amdahl.amdahl.com>
Date: Wed, 26-Aug-87 14:00:57 EDT
Article-I.D.: amdahl.12956
Posted: Wed Aug 26 14:00:57 1987
Date-Received: Fri, 28-Aug-87 06:19:43 EDT
References: <855@tjalk.cs.vu.nl> <2683@hoptoad.uucp> <916@haddock.ISC.COM> <1580@sol.ARPA> <294@rruxa.UUCP>
Reply-To: esf00@amdahl.amdahl.com (Elliott S. Frank)
Organization: The Beige Building Full of Bright Engineers, Inc.
Lines: 47
Xref: mnetor comp.lang.c:3929 comp.arch:1947

In article <294@rruxa.UUCP> gwl@rruxa.UUCP (George W. Leach) writes:
>
>     What I would like to take issue with is the longevity of the 360/370
>architecture.  Is it really the adaptability and flexibility of the
>architecture or is it the fact that the huge customer base is tied into
>that IBM environment?  There is a tremendous amount of $$$$ invested in
>COBOL, FORTRAN and PL/1 code on those beasts that CAN NOT be moved easily
>to another architecture.  This is due to such nice IBM-ONLY features,
>such as EBCIDIC character sets.
>
>     On the other hand, the $$$$ invested in code written in C under
>UNIX is easily ported (if written with portability in mind) to other
>architectures as they come along.  Thus one can take advantage of new
>advances in computer architecture without the pain and cost of moving
>unportable code.
>
Having spent most of the past twenty years working in the 360/370
environment, "there is truly nothing new under the sun."  It is as
possible to write machine dependant code in C in a UNIX environment
(cf the "how many bits are in an int, and which is the low-order one"
discussion recently concluded in this newsgroup) as is to write portable
COBOL in the EBCDIC MVS eenvironment.

If you stick to a single machine architecture and operating system
environment, machine-to-machine migration becomes a problem of power
cables and air conditioning.  This becomes a very powerful economic
argument for sticking with that single machine architecture.  VAX VMS
has ensured its survival for the same reason.  You can move an
application from an 11/750 (running VMS) to an 8650 (also running VMS)
with minimal porting effort.

Despite the CISC aggregations that have grown up on the original 360
instruction set (Niklaus Wirth did not include support for the BXH and
BXLE [decrement {increment} index and test against limit] instructions
in his pioneering PL/360 structured assembler) (can you say "Compare
and Form Codeword" or "Update Tree"?)) the longevity of the 360/370
architecture has come from the simplicity of most of the instructions.


-- 

Elliott S Frank    ...!{hplabs,ames,seismo,sun}!amdahl!esf00     (408) 746-6384
                or ....!{bnrmtv,drivax,hoptoad}!amdahl!esf00

[the above opinions are strictly mine, if anyone's.]
[the above signature may or may not be repeated, depending upon some
inscrutable property of the mailer-of-the-week.]