Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site rlgvax.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!rlgvax!guy
From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.lang.c
Subject: Re: Re: derived types
Message-ID: <412@rlgvax.UUCP>
Date: Fri, 1-Feb-85 17:39:18 EST
Article-I.D.: rlgvax.412
Posted: Fri Feb  1 17:39:18 1985
Date-Received: Sun, 3-Feb-85 09:42:02 EST
References: <7479@brl-tgr.ARPA> <37@gitpyr.UUCP> <6873@watdaisy.UUCP> <53@gitpyr.UUCP> <383@lll-crg.ARPA>
Organization: CCI Office Systems Group, Reston, VA
Lines: 24

> > The CDC 170 series doesn't support reals larger than 60-bits in the hardware.
> > It can be done, but only through software.  C is defined to calculate all
> > real numbers as doubles.  This means that there'll be a lot of wasted time
> > spent doing something the machine can't do with it's native instruction set.
> 
> This stupidity, due to how the hardware on the FP11 worked (do you guys out
> there even remember the PDP11?), ended up in the language definition.  No
> sensible compiler writer would kill floating point performance like these
> days.

It didn't even *have* to be done for the PDP-11; DEC's Fortran-IV Plus
compiler quite happily generated all the "setf"/"setd" instructions needed
to do single-precision arithmetic.  However, it may not have been worthwhile
to go through the hair involved for doing that in C.

> Its time we removed this stupidity from the language definition proper and
> turned the compatibility problem over to lint!

The current ANSI Standard C draft, I believe, leaves it up to the compiler
writer to decide whether to do floating point arithmetic in single or double
precision.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy