Path: utzoo!utgpu!cunews2!cunews!cognos!jimp
From: jimp@cognos.UUCP (Jim Patterson)
Newsgroups: comp.arch
Subject: Re: ieee floating standard
Message-ID: <9664@cognos.UUCP>
Date: 23 May 91 13:04:39 GMT
References: <9105220041.AA14355@ucbvax.Berkeley.EDU> <1991May22.221824.16887@riacs.edu>
Reply-To: jimp@cognos.UUCP (Jim Patterson)
Organization: Cognos Inc., Ottawa, Canada
Lines: 25

In article <1991May22.221824.16887@riacs.edu> lamaster@pioneer.arc.nasa.gov (Hugh LaMaster) writes:

>1)  It is a standard.  It is very important to certain users to be able to
>move binary data between machines without conversion.

This isn't quite correct. While IEEE specifies quite a bit about the
format of its floating point representations, it leaves unsaid a few
details such as endian-ness. The 80x87 chips, for example, follow
INTEL convention and represent floats in little-endian format (the
sign bit is at the highest address, not the lowest). Representations
of the extended precision formats are also not pinned down; 80x87 uses
80 bit extended while other implementations e.g. HP-PA use a 128 bit
extended precision. (This is an internal format, though; not a lot of
need to transfer it around between machines).

So, while you might get by with doing at most a byte-swap to move IEEE
floats around, you can't blindly assume that all IEEE floats are the
same.


-- 
Jim Patterson                              Cognos Incorporated
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