Re: Accumulator naming

From	cross@spitfire.i.gajendra.net (Dan Cross)
Newsgroups	alt.sys.pdp10
Subject	Re: Accumulator naming
Date	2026-07-31 02:52 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<114h2ll$bf6$1@reader1.panix.com> (permalink)
References	<87wlulwflh.fsf@atr2.ath.cx> <mddv79wjdc8.fsf@panix5.panix.com> <114gnt0$pds$1@reader1.panix.com> <114gtt5$ul5$1@gal.iecc.com>

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In article <114gtt5$ul5$1@gal.iecc.com>, John Levine  <johnl@taugh.com> wrote:
>According to Dan Cross <cross@spitfire.i.gajendra.net>:
>>In article <mddv79wjdc8.fsf@panix5.panix.com>,
>>Rich Alderson  <news@alderson.users.panix.com> wrote:
>>>[snip]
>>>MP=     16                      ;MACRO PUSHDOWN POINTER
>>>P=      17                      ;BASIC PUSHDOWN POINTER
>>
>>Just a meta note, not a comment on register naming conventions,
>>but I the "pushdown" terminology interesting here.  Was this
>>common then?  When did it become common to call it a "stack" as
>>we'd typically do these days?
>
>It was and is a pushdown stack. The analogy is the stack of dishes in
>a cafeteria on a spring loaded tray. As you put more dishes on it the
>stack pushed down the spring so there were always just a few visible
>on the top, and as you took dishes off, they popped back up.
>
>Here's some pictures of one:
>
>https://www.katom.com/121-401125.html
>
>This was well known when I was in school in the late 1960s and 1970s.

No, I understand that it is a pushdown stack, and I'm familiar
with the dishes analogy (my school cafeterias had similar
contraptions 20 years after yours and I've heard it in this
context before).

My question was specifically about the nomenclature: in the
above examples, the register alias is simply called "P" for
"pushdown", omitting the "stack" part; modern terminology
usually (always?) omits the "pushdown" part and simply calls it
a "stack".  For example, assemblers for many ISAs will
conventionally label a general purpose register the "SP", for
stack pointer (regardless of whether such a register is used
that way by hardware, or simply by software convention).

My question was whether the former convention was common at the
time, and if so, when did it change?

	- Dan C.

Thread

Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-23 17:39 -0400
  Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-23 23:19 -0400
    Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-25 12:00 -0400
      Re: Fizz Buzz Rich Alderson <news@alderson.users.panix.com> - 2026-07-25 18:05 -0400
        Re: Fizz Buzz jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-26 11:12 -0400
      Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-29 18:10 -0400
        Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 15:14 +0000
          Re: old architectures, was Accumulator naming John Levine <johnl@taugh.com> - 2026-07-30 20:40 +0000
          Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:41 -0400
        Re: Accumulator naming jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-07-30 11:24 -0400
          Re: Accumulator naming scott@slp53.sl.home (Scott Lurndal) - 2026-07-30 16:03 +0000
          Re: Accumulator naming Rich Alderson <news@alderson.users.panix.com> - 2026-07-30 18:56 -0400
            Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-30 23:48 +0000
              Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 01:31 +0000
                Re: Accumulator naming cross@spitfire.i.gajendra.net (Dan Cross) - 2026-07-31 02:52 +0000
                Re: Accumulator naming John Levine <johnl@taugh.com> - 2026-07-31 03:36 +0000
                Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:40 +0000
          Re: Accumulator naming Lars Brinkhoff <lars.spam@nocrew.org> - 2026-07-31 13:35 +0000
          the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-11 16:07 -0300
            Re: the Ten Heavenly Stems (was Re: Accumulator naming) Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-09-14 01:12 +0800
              Re: the Ten Heavenly Stems (was Re: Accumulator naming) Kragen Javier Sitaker <kragen@canonical.org> - 2026-09-14 14:40 -0300
                Re: the Ten Heavenly Stems (was Re: Accumulator naming) scott@slp53.sl.home (Scott Lurndal) - 2026-09-14 18:09 +0000
                Re: the Ten Heavenly Stems (was Re: Accumulator naming) quadibloc@invalid.com (John Savard) - 2026-10-26 03:00 +0000
  Re: Fizz Buzz "Kerr-Mudd, John" <admin@127.0.0.1> - 2026-08-21 13:27 +0100

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