Xref: news2.mv.net comp.os.msdos.djgpp:5011
From: Erik Max Francis <max AT alcyone DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: How are bool's allocated?
Date: Fri, 14 Jun 1996 23:12:26 -0700
Organization: Alcyone Systems
Lines: 30
Message-ID: <31C2544A.3963D6DF@alcyone.com>
References: <4pp82v$qd4 AT usenet DOT rpi DOT edu>
NNTP-Posting-Host: newton.alcyone.com
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

David J. Calvin wrote:
> 
> In DJGPP, how is memory allocated for bool variables?  Is just
> 1 bit allocated, or a whole byte?  If you do sizeof(bool), it
> returns 1, but maybe that's just a limitation of sizeof().
> I'm planning on using a large number of bool's in a structure,
> and I was wondering if it would be more efficient to declare
> them all as bool's, or to use unsigned characters and use
> bitwise ops to access each bit that way.  Thanks for the info.

All I have in front of me is _The design and evolution of C++_; it doesn't
specify the size of a bool.  However, it also specifies that bool is _not_
simply an enumerated type defined as

     enum bool { false, true };

In the current draft C++ standard, bool is a fundamental datatype with
interesting implicit conversion behaviors that make it behave like one would
expect.

Packing Booleans as bits is easy, but it takes more than the usual amount of
processor work.  Usually you don't want to do this and it's worth it to waste
seven extra bits to gain the extra speed.

-- 
Erik Max Francis &tSftDotIotE && http://www.alcyone.com/max && max AT alcyone DOT com
San Jose, California, U.S.A. && 37 20 07 N 121 53 38 W && the 4th R is respect
H.3`S,3,P,3$S,#$Q,C`Q,3,P,3$S,#$Q,3`Q,3,P,C$Q,#(Q.#`-"C`- && 1love && folasade
Omnia quia sunt, lumina sunt. && Dominion, GIGO, GOOGOL, Omega, Psi, Strategem
"Out from his breast/his soul went to seek/the doom of the just." -- _Beowulf_