Xref: utzoo comp.lang.c:8152 comp.arch:3925
Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Bit Addressable Architectures
Message-ID: <7452@brl-smoke.ARPA>
Date: 14 Mar 88 03:56:36 GMT
References: <11702@brl-adm.ARPA> <243@eagle_snax.UUCP> <2245@geac.UUCP> <1988Mar6.002518.945@utzoo.uucp> <2760@mmintl.UUCP> <17458@watmath.waterloo.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 23

In article <17458@watmath.waterloo.edu> ccplumb@watmath.waterloo.edu (Colin Plumb) writes:
>This can't be a new idea.  Why has no one implemented it before, when
>32-bit pointers seemed infinite?  Perhaps that will uncover a flaw in
>my reasoning.

It's occasionally been tried, and there is nothing fundamentally wrong with
the idea.  The biggest reason for lack of popularity is that it doesn't help
much with the code generated for typical existing high-level langauges; they
often don't provide convenient access to bit-level data, so applications are
coded to access data in larger chunks and pick it apart themselves.

If direct bit-operation support is not built into some popular systems
programming language (such as a C successor), there will be little
incentive for manufacturers to provide the underlying hardware support.

The main categories of applications I've been involved in that would benefit
from being able to access bits as conveniently as words/bytes are:
	bit-map graphics (especially black-and-white)
	data compression
	encryption (also cryptanalysis of machine ciphers)
	bottom-up parsing (e.g. transitive closure of Boolean matrices)
	simulation
I'm sure there are others.