> On19 Feb 2025 18:39:08 -0500, Chuck Guzis via cctalk wrote:
>
>>>
>>>> One of most ingenious coding tricks to me was the problem of saving and
>>>> restoring all registers without resorting to an exchange jump. We used
>>>> that one as a test for applicants.
>>>
>>> Argh... I know I've seen this trick, but it's been too many years. How
>>> about a hint?
>>
>> It uses the RJ instruction to record register content, bit-by-bit.
>> Think about it--RJ is about the only instruction that can modify memory
>> without fiddling with the A6 and A7 registers.
>>
>
> Of course... I vaguely recalled there was a bit-by-bit save, but didn't
> think of the RJ. Thanks.
A full example of this code is in the DEBUG package of CAL SNOBOL <https://mcjones.org/CAL_SNOBOL/>, starting at label SAVEREG:
Original version: https://mcjones.org/CAL_SNOBOL/UArizona/SNOBOL.MAC.html
Revised version: https://mcjones.org/CAL_SNOBOL/UTexas/DEBUG.html
I saw an email posted to the predecessor mail list asking if anyone had a picture of an IBM 4506 terminal. I was looking through the September 1973 issue Modern Data and saw an article on page 70 about the New York Times’s indexing efforts. It said that they were using IBM 4506 terminals and it has a picture of a large workroom (identified as “The Times index room”) with a bunch of terminals which I assume must be 4506’s (although the caption does not explicitly state that). The magazine is available on BitSavers. Look for the issue with file name Modern_Data_1973_07.pdf.
Tommy Chang
Did any classic computers have a subroutine call as (S++)=PC, PC=(EFA)
as well as the standard call (--S)=PC,PC=(EFA) ?
One could have a virtual stack machine, using helper functions without
having to deal with return addresses on the stack.
Ben.
On Tue, 18 Feb 2025 12:00:10 -0600
cctalk-request(a)classiccmp.org wrote:
> On the more than "one stack pointer" in the subject, it was a bit
> arbitrary on the PDP-11 (or VAX) as the pre/post indexed indirect
> addressing made every register a stack pointer. But this is where I
> get hazy between DEC and 68K, and I did a lot more 68K. I'm pretty
> sure you could do a move.l PC, An and you could certainly do an
> indirect jmp (An), so effectively you could have multiple call stacks
> if you wanted.
Almost, kinda-sorta. The JSR and RTS instructions are hard-wired to use
R6/SP, and there's nothing you can do about that. You *can* implement a
return off another "stack" by doing e.g. MOV @(Rn)+, PC as long as you
save the return address by hand, first - but this affects the flags,
unlike JSR/RTS.
> On 15 Feb 2025 18:41:21 -0800,Van Snyder <van.snyder(a)sbcglobal.net <mailto:van.snyder@sbcglobal.net>> wrote:
>
> Harry Husky, the G15 designer, was one of the computer design pioneers.
> He became a professor (maybe adjunct) at UC Berkeley.
As far as I know, Huskey was a regular professor. Two of his Ph.D. students went on to win the ACM Turing Award: Niklaus Wirth and Butler Lampson:
https://mathgenealogy.org/id.php?id=10185
Huskey went on to found the Computer Science department at U.C. Santa Cruz.
> On 16 Feb 2025 18:00:35 -0700,ben <bfranchuk(a)jetnet.ab.ca <mailto:bfranchuk@jetnet.ab.ca>> wrote:
>
> I have trouble understanding the fine points of accessing a local
> variable in Algol with a display. Books tend to spend more time
> on the evils of a dangling else, and gloss over the run time action of
> a display.
> Have a good example or reference book I can find free on line.
The original book on that subject is ALGOL 60 Implementation by B. Randell and L. J. Russell. It’s available here with permission from the copyright holder:
https://www.softwarepreservation.org/projects/ALGOL/algol60impl/#ALGOL_60_I…
I am an old mainframe guy. I could give you my COBOL deck of cards or the compile listing. You could pour through the code looking for nefarious/malicious code. I then hand you the object deck. You have no idea if it matches the code you looked at. The only way you could be sure is to compile the code I gave you and use your own object deck.
So why is open source these days such a beneficial thing? DeepSeek may be open source but I have no way to create my own executable. Besides, I don’t know what language it is written in but I bet I have no expertise in it. No way to for me to identify nasty code.
Yes, many people may have reviewed the code but that does not mean what I am running is the result of that code.
Hi Van,
just wanted to point out, that there is a 803 emulator out there:
https://www.peteronion.org.uk/Elliott/
I have got a real 900 series machine running, which is from the very
early 1970ies and also runs a form of Elliott Algol:
https://www.youtube.com/watch?v=v-gF5g0nnoE
Best wishes,
Erik.
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