Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!sundc!hadron!jsdy
From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: comp.arch,comp.lang.c
Subject: Re: sizeof(char)
Message-ID: <626@hadron.UUCP>
Date: Mon, 24-Nov-86 01:40:05 EST
Article-I.D.: hadron.626
Posted: Mon Nov 24 01:40:05 1986
Date-Received: Mon, 24-Nov-86 21:54:54 EST
References: <4617@brl-smoke.ARPA> <657@dg_rtp.UUCP>
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Organization: Hadron, Inc., Fairfax, VA
Lines: 19
Summary: Bit field addressing?
Xref: mnetor comp.arch:59 comp.lang.c:151

In article <3853@mit-eddie.MIT.EDU> jbs@eddie.MIT.EDU (Jeff Siegal) writes:
>In article <9116@sun.uucp> guy@sun.uucp (Guy Harris) writes:
>>The MicroVAX-II supports the *bit field instructions of the VAX*.  This is
>>*not* the same as supporting "bit addressing".
>In the general sense, no, but you can move any string of up to 32 bits
>from any bit boundry in memory to any other.

I'm surprised Guy didn't jump on this (or did we just miss it?).
The Vax EXTV/EXTZV and INSV (and CMPV/CMPZV) instructions go
between an arbitrary string of 0-32 bits and a byte-aligned
longword of 4 8-bit bytes.  Not the same as any 0-32 bits to
any 0-32 bits.  If I want to move bits 4-19 of word 10 to bits
5-20 of word 14, I'd have to do an EXTZV/INSV pair, clobbering
a longword somewhere in memory (or a register) as a temporary
holding place.
-- 

	Joe Yao		hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}
			jsdy@hadron.COM (not yet domainised)