Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!ptsfa!ihnp4!alberta!ubc-vision!ubc-cs!manis
From: manis@ubc-cs.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: MWC and VAX floating-point format
Message-ID: <1475@ubc-cs.UUCP>
Date: Fri, 19-Jun-87 10:57:18 EDT
Article-I.D.: ubc-cs.1475
Posted: Fri Jun 19 10:57:18 1987
Date-Received: Sun, 21-Jun-87 04:59:37 EDT
References: <8706171715.AA08471@orville.arpa>
Reply-To: manis@ubc-cs.UUCP (Vincent Manis)
Distribution: world
Organization: UBC Department of Computer Science
Lines: 29

In article <8706171715.AA08471@orville.arpa> rowley@ORVILLE.ARPA.UUCP (Karl
Rowley) writes:

>VAX double-precision format is identical to single-precision format, except
>that the mantissa is extended.  The IEEE format does not have this property.

Actually (not really being an expert in these matters) I believe that what 
MWC uses is the old PDP-11 format. VAXen nowadays have 4 (!) formats, of
which MWC appears to use F (single) and D (old double) precision. Not having
the VAX G format (less than double, but with more exponent bits) is something
of a lose, in that one gets possibly more precision, but no more range.
Since I rarely use floating point, I don't care that much. However, not
having the same format as used by other ST languages is a bit of an
annoyance, as is the inability to support coprocessors.

>Of course, IEEE format is superior in many ways, and doesn't have its bytes
>all flipped around.

They could have done *much* worse. The 370 has its own floating point format.

-----
Vincent Manis                {seismo,uw-beaver}!ubc-vision!ubc-cs!manis
Dept. of Computer Science    manis@cs.ubc.cdn
Univ. of British Columbia    manis%ubc.csnet@csnet-relay.arpa  
Vancouver, B.C. V6T 1W5      manis@ubc.csnet
(604) 228-6770 or 228-3061

"To lose one parent, Mr Worthing, may be regarded as a misfortune; but
to lose both looks like carelessness." -- Oscar Wilde