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Namir · (This post was last modified: 09-24-2020 08:39 PM by Namir.)

Hi All,

A few months ago I downloaded a pdf file that contains a library of HP-25 programs (which I believe was published in the PPC journal (???)), many of which were written by James Davidson and other PPC members. I must admit that I am very impressed with Davidson's work who was able to squeeze cool math programs in the 49 steps (and less!) of the HP-25 (and remember that calculator has no subroutine support). I am currently looking at Newton's method as implemented by Davidson. I had to use an Excel spreadsheet to document/trace program execution for one iteration, keeping track of what's in the stack and the four memory register used. All I can say is WOW! In the absence of subroutines (normally needed to make coding Newton's method easy), Davidson has shown fantastic programming skills in being able to execute the code for function f(x) twice per iteration. His manipulation of the memory register that stores the tolerance value (which he also uses as a logical flag) is nothing short of genius!!! My hats of for James!!

Davidson has also programs for solving differential equations and Simpson's method that use very clever programming tricks!!!

Another person who comes to mind who has mastered coding math functions in the HP-25 is the late Swiss professor Peter Henrici who taught at ETH in Zurich. Henrici wrote (for Wiley) a book about coding math programs for the HP-25, pushing the HP-25 to its limits! Later, Peter and his wife wrote a similar book for the HP-33E (which had line-oriented subroutines).

Programmers like Davidson and Henrici (to name a few) illustrate clever and frugal use of machine resources. The advent of the PC with it's ever increasing memory and disk resources has spoiled our programming practices.

Namir

**rprosperi** · 09-24-2020, 09:44 PM

Thanks Namir.

Lots of folks here like and use HP-25s, can you share the PDF file you mentioned? If it's from PPC, there's no doubt the author's intended it to be shared.

Valentin Albillo · 09-24-2020, 09:46 PM

(09-24-2020 08:37 PM)Namir Wrote: [...] a library of HP-25 programs [...] many of which were written by James Davidson [...]

Davidson has shown fantastic programming skills in being able to execute the code for function f(x) twice per iteration.

Not to belittle that gentleman's work but if you're so impressed with "being able to execute the code for function f(x) twice per iteration" on a max. 49-step calc with no subroutine capability, I wonder what would you think of the two HP-25 programs featured in this PDF document:

            Long Live the HP-25

            - the first one is 36-step long, leaves 13 steps to define the function, and evaluates it three times per iteration, with different arguments each time.

            - the second one is 39-step long, leaves 10 steps to define the function, and evaluates it four times per iteration, with different arguments each time.

I think I've told you about them several times in the past but you seem to forget ever mentioning them.

V.

Dave Frederickson · (This post was last modified: 09-24-2020 10:26 PM by Dave Frederickson.)

(09-24-2020 09:44 PM)rprosperi Wrote: Lots of folks here like and use HP-25s, can you share the PDF file you mentioned? If it's from PPC, there's no doubt the author's intended it to be shared.

Here's a link. Oh, hey! Smile

https://hpmuseum.org/forum/thread-7236-p...l#pid97834

**Gene** · 09-24-2020, 11:23 PM

I pulled that PDF together from the PPC Journal articles to make sure the HP-25 materials did not disappear. Great stuff...

**rprosperi** · 09-25-2020, 12:57 AM

(09-24-2020 10:25 PM)Dave Frederickson Wrote:
(09-24-2020 09:44 PM)rprosperi Wrote: Lots of folks here like and use HP-25s, can you share the PDF file you mentioned? If it's from PPC, there's no doubt the author's intended it to be shared.

Here's a link. Oh, hey!

https://hpmuseum.org/forum/thread-7236-p...l#pid97834

Oh! That collection... Like I remember names or applications.... LOL... Ahem..

teenix · 09-25-2020, 07:06 AM

(09-24-2020 08:37 PM)Namir Wrote: Hi All,

A few months ago I downloaded a pdf file that contains a library of HP-25 programs (which I believe was published in the PPC journal (???)), many of which were written by James Davidson
and other PPC members. I must admit that I am very impressed with Davidson's work who was Namir

I think I have already prepared those files as programs for the Teenix emulator.

http://www.teenix.org/HP25ppc.zip

cheers

Tony

Namir · 09-25-2020, 09:33 AM

(09-24-2020 11:23 PM)Gene Wrote: I pulled that PDF together from the PPC Journal articles to make sure the HP-25 materials did not disappear. Great stuff...

Yes its the file that you shared on a past thread.

Namir

**rprosperi** · 09-25-2020, 12:09 PM

Thanks Namir and Tony.

And thank goodness it wasn't the other one that I had shared earlier... Smile

Jake Schwartz · 09-25-2020, 06:58 PM

Yep, when the second PPC Member Handbook was being assembled in 1979, we did a PPC "Hall of Fame" (listed on page 154) and Jim Davidson was right up there after Richard Nelson. He had already contributed 50 HP25 programs by that time. In addition, the entire handbook was dedicated to him, as shown on page 1. Jim sadly passed away on 1/15/79.

Jake

Werner · 09-26-2020, 11:05 AM

(09-24-2020 09:46 PM)Valentin Albillo Wrote: - the second one is 39-step long, leaves 10 steps to define the function, and evaluates it four times per iteration, with different arguments each time.

Hello Valentin,
the library actually contains a 4th-order Runge-Kutta integration routine as well (L18), that leaves 16 steps free for the definition of f(x,y). It uses a counter in R5 to distinguish between the function calls.

Cheers, Werner