From: Clem Cole <clemc@ccc.com>
To: Noel Chiappa <jnc@mercury.lcs.mit.edu>
Cc: tuhs@minnie.tuhs.org
Subject: Re: [TUHS] [tuhs] PDP-11 and early Unix
Date: Mon, 14 Mar 2022 14:00:32 -0400 [thread overview]
Message-ID: <CAC20D2OMk1F9hNFfvEfETa4J_Y54HNLr54v8QPZax+VnA2cdeA@mail.gmail.com> (raw)
In-Reply-To: <20220314165604.4889918C075@mercury.lcs.mit.edu>
[-- Attachment #1: Type: text/plain, Size: 1240 bytes --]
On Mon, Mar 14, 2022 at 12:59 PM Noel Chiappa <jnc@mercury.lcs.mit.edu>
wrote:
>
>
> Not a bad artcle, but it had a number of minor errors, which I found
> irritating.
> They should have gotten an expert to proof it.
>
Sure - but usually these are way more bad than good. Usually way too
much urban legend, so I'm thrilled to see the 11 kept alive.
>
> And a tip of the hatly hat for getting this:
>
> Although the ++ and - operators in C are equivalents of DEC and INC
> instructions, they were inspired by an addressing mode in the PDP-7.
>
As I said, the authors seem to have done a little homework, although I was
under the impression ??Ken?? had created them for B independently (which,
of course, was first on the PDP-7). The ++/-- for increment and decrement
was just a nice notation since they are such a common occurrence in real
code, it's handy to have. But, I did not think the PDP-7 ISA includes
addressing modes in the same manner as the 11. I'm probably confused, but
I thought PDP-7 is a very simple instruction (and small) with an AC,
Link/Indirection and a PC - it reminded me of the PDP-8 more than anything
else [although, IIRC it could do both 1's complement and 2's - depending
the type of AND instruction].
[-- Attachment #2: Type: text/html, Size: 2134 bytes --]
next prev parent reply other threads:[~2022-03-14 18:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-14 16:56 Noel Chiappa
2022-03-14 18:00 ` Clem Cole [this message]
2022-03-14 19:03 ` Angelo Papenhoff
-- strict thread matches above, loose matches on Subject: below --
2022-03-14 20:38 Noel Chiappa
2022-03-14 20:22 Noel Chiappa
2022-03-14 12:58 Nelson H. F. Beebe
2022-03-14 14:59 ` Ron Natalie
2022-03-14 15:13 ` Clem Cole
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=CAC20D2OMk1F9hNFfvEfETa4J_Y54HNLr54v8QPZax+VnA2cdeA@mail.gmail.com \
--to=clemc@ccc.com \
--cc=jnc@mercury.lcs.mit.edu \
--cc=tuhs@minnie.tuhs.org \
/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).