Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site brl-vgr.ARPA
Path: utzoo!watmath!clyde!burl!ulysses!harpo!seismo!brl-tgr!brl-vgr!gwyn
From: gwyn@brl-vgr.ARPA (Doug Gwyn )
Newsgroups: net.lang.c
Subject: Re: Numerical C
Message-ID: <1206@brl-vgr.ARPA>
Date: Tue, 1-May-84 18:18:49 EDT
Article-I.D.: brl-vgr.1206
Posted: Tue May  1 18:18:49 1984
Date-Received: Wed, 2-May-84 06:34:01 EDT
References: <3000022@uokvax.UUCP>, <882@elsie.UUCP>
Organization: Ballistics Research Lab
Lines: 18

I think all three answers (as to why floats are promoted to doubles in C)
are applicable, with the amendment that the PDP-11 floating-point
processors (FP11s) do not necessarily work in double-precision, but
one has to change their mode back and forth to change from double-
precision to single-precision arithmetic, so it was simpler to just
leave the mode in double-precision all the time (code starts with a
SETD instruction to do this).

PDP-11 floating-point has never been really satisfactory anyway.  It is
very hard (but not impossible) to share the FP11 coprocessor among
multiple processes; early UNIXes did not properly save & restore the
FP11 status upon context switch due to the ansynchronism of the beast.
Whoever first introduced 32-bit integers along with the FP11 really
botched the job, and these weren't straightened out until the VAX
(which is otherwise binary data compatible with the PDP-11).

I rather like having all my arithmetic done in double-precision, though.
VAX & PDP-11 single-precision isn't good for much serious computation.