From: txomsy@yahoo.es (Jose R Valverde)
Subject: [TUHS] Having trouble with V6 source code
Date: Mon, 2 Oct 2006 16:24:07 +0200 (CEST) [thread overview]
Message-ID: <20061002142407.69090.qmail@web26109.mail.ukl.yahoo.com> (raw)
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain, Size: 1770 bytes --]
No.
On PDP 11 assembler the left and right shifts were a single < and >.
You made a typo when transcribing the source statement: you typed
> 0636: mov $USIZE-1/<8|6, (r1)+
but the actual code from m40.s reads
> 0636: mov $usize-1\<8|6,(r1)+
However, since < and > where also used to delimit strings, there was a
need to escape them so as to distinguish their usage as shifts from the
string delimiters. The escaping was achieved by \ which is what you see
in the code.
See the assembler section of vol 2b of the Unix V7 manuals for details at
http://plan9.bell-labs.com/7thEdMan/v7vol2b.pdf
or
http://web.cuzuco.com/%7Ecuzuco/v7/v7vol2b.pdf
namely:
6.1 Expression operators
The operators are:
(blank) when there is no operand between operands, the effect is
exactly the same as if a + had appeared.
+ addition
subtraction
* multiplication
\/ division (note that plain / starts a comment)
& bitwise and
| bitwise or
\> logical right shift
\< logical left shift
... ... ...
j
On Mon, 2 Oct 2006 09:44:58 +0300
jigsaw <jigsaw at gmail.com> wrote:
> hi all,
>
> I just started to read the source code of V6 with Lion's book.
>
> But before I went far I was stopped by m40.s
>
> 0636: mov $USIZE-1/<8|6, (r1)+
>
> What does the slash "/" stand for?
>
> I guess this line should be
>
> mov $USIZE-1<<8|6, (r1)+
>
> Is "/<" the same as "<<"?
>
> I checked in Unix PDP11 Assemble Refrence Manual but didn't find a clue.
>
> Is it the right place to ask such question?
>
> Thanks in advance
>
> Regards,
>
> Qinglai
______________________________________________
LLama Gratis a cualquier PC del Mundo.
Llamadas a fijos y móviles desde 1 céntimo por minuto.
http://es.voice.yahoo.com
next reply other threads:[~2006-10-02 14:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-02 14:24 Jose R Valverde [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-10-03 12:25 Wolfgang Helbig
2006-10-02 14:22 Jose R Valverde
2006-10-02 15:24 ` jigsaw
2006-10-02 6:44 jigsaw
2006-10-02 12:50 ` Hans Rosenfeld
2006-10-02 12:59 ` jigsaw
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20061002142407.69090.qmail@web26109.mail.ukl.yahoo.com \
--to=txomsy@yahoo.es \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).