Newsgroups: comp.lang.c
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Here's a challenge for floating point lovers.
Message-ID: <1991Jan29.173341.11899@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <14964@smoke.brl.mil> <101@tdatirv.UUCP> <2855@charon.cwi.nl> <14993@smoke.brl.mil> <3322@unisoft.UUCP>
Date: Tue, 29 Jan 1991 17:33:41 GMT

In article <3322@unisoft.UUCP> greywolf@unisoft.UUCP (The Grey Wolf) writes:
>How many different floating point formats are there out there?  I'm
>aware of IEEE and VAX.  Are there any others, and what are the pros and
>cons?

There are lots of them.  Even on the VAX there are two generations of
incompatible formats -- the original ones were pdp11-compatible, while
the later ones improved on that.  In the days before IEEE format, every
manufacturer had his own, and often more than one.  You can find the
occasional floating-point chip that can speak three or four different
formats on request.

In general, despite Doug's distaste for its complexity, IEEE floating
point is an order of magnitude superior to the rest.  It was designed
by people who understood numerical arithmetic.  That may sound obvious,
but the fact is that a lot of the older formats were designed more for
hardware convenience than for good numerical properties.

Nobody (well, except maybe Seymour Cray, who has other constraints
to think about) designs new machines using anything other than IEEE.
-- 
If the Space Shuttle was the answer,   | Henry Spencer at U of Toronto Zoology
what was the question?                 |  henry@zoo.toronto.edu   utzoo!henry