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I was bored and found a HP-27S
06-27-2014, 02:21 PM
Post: #51
RE: I was bored and found a HP-27S
(06-27-2014 01:15 PM)jebem Wrote:  
(06-27-2014 12:43 PM)rprosperi Wrote:  Jebem - You've got some catching up to do with your newest toy

Sure, I got the idea... the way Thomas and others took advantage of the Solver feature and managed to twist it into a kind of a programming environment was the reason why I did chase for a HP-27S... I just had to have it!

Actually I was chasing a HP-42S since long time ago (I got it As-New-in-the-Box just yesterday evening!), and I found the HP-27S by accident by reading the related intriguing publications from Thomas, Don, Bob, Luiz and many others here in the MoHPC archives... Thank you all for that!

But even using the Solver in the formal documented way, it is amazing on how easy and fast is to type in a formula with basic logic conditions to solve common problems, without the need to spend time creating programs (as in the other calculator paradigms of the time), and this was available from HP in the 80's!

I read in an old HP Journal somewhere a few years ago that Paul McClellan was the principal designer at HP responsible for the solver in the 17b/27s series. I had always wondered if the designers of the solver had put in a hidden command to write to a sum list. You can read from a sum list via the ITEM command, but you can't write to a sum list from an equation. If you could, it would open up the solver to all kinds of additional applications.

I wrote to Mr. McClellan and he responded. I don't think he would mind if I showed his response here, because I think many of us would find this very interesting.

My letter to him:
Quote:Paul, while reading an old HP Journal, I came across your name as the principal developer of the HP Solve application which is used in the HP-18c, 28s, 17b, 19b, and 27s I believe. I'm a big fan of that app, and my hobby is to see how solve can be used as a programming language in those calculators.



Can you answer a question for me? I've wondered for years now why the L() and G() commands were not included in the respective calculator manuals; instead they were described in the Technical Applications Manual for the 27s/19b. I've theorized that maybe L and G were created for debugging the solver and were left in the production code by accident, and then people found out about them. Can you shed any light on that?



Also, for years I've wished that there was a hidden solver function for writing to a sum list. I figure you'd be the guy to know if there was one.



Thanks Paul.

Paul's response:

Quote:Hi Don,



It has been decades since I helped design and implement HP Calculators, but it was one of my favorite times while working at Hewlett-Packard – we put a lot of craft into those little machines and hopefully they delighted many thousands of our customers.



I must credit Prof. William H. Kahan (former Professor of Mathematics and Computer Science at UC Berkeley) as the author of the HP calculator numerical solver algorithm. I and others implemented and tested the numerical solver function across several calculators. This numerical solver algorithm was also used with argument and function scaling in the financial functions. I have attached two PDFs, both written by Prof. Kahan. One is an HP Journal article describing the HP-34C’s solver function (the first implementation of the algorithm on an HP calculator). The other “Mathematics Written in Sand” gives more background on the numerical solver project.



Charles Patton designed and implemented our symbolic solver, and I recollect he had a lot of input into the user interface for the combined symbolic/numeric solver functionality. Charles likely created the L() and G() functions you refer to – I don’t recollect having much direct experience using them. I have cc’ed Charles using what email address I have at this time.



Can you describe more fully what you mean by a solver function for writing to a sum list?



Thank you for your inquiry. I have recently retired from HP and am pursuing personal interests, including writing computational software, exploring website development technologies, and especially enjoying outdoor recreation in the western US.



Best regards,

Paul McClellan

These guys were brilliant to have built a solver with so many advanced capabilities. My hat is off to them.
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Messages In This Thread
I was bored and found a HP-27S - jebem - 06-09-2014, 10:38 PM
RE: I was bored and found a HP-27S - jebem - 06-10-2014, 09:35 AM
RE: I was bored and found a HP-27S - jebem - 06-25-2014, 06:49 PM
RE: I was bored and found a HP-27S - jebem - 06-26-2014, 01:44 PM
RE: I was bored and found a HP-27S - jebem - 06-26-2014, 01:40 PM
RE: I was bored and found a HP-27S - jebem - 06-26-2014, 03:57 PM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 01:15 PM
RE: I was bored and found a HP-27S - Don Shepherd - 06-27-2014 02:21 PM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 08:50 PM
RE: I was bored and found a HP-27S - HP67 - 06-27-2014, 02:56 PM
RE: I was bored and found a HP-27S - HP67 - 06-27-2014, 03:28 PM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 10:18 PM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 10:58 PM
RE: I was bored and found a HP-27S - jebem - 06-28-2014, 08:02 AM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 10:46 PM
RE: I was bored and found a HP-27S - jebem - 06-28-2014, 07:55 AM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 10:56 PM
RE: I was bored and found a HP-27S - jebem - 06-27-2014, 11:05 PM
RE: I was bored and found a HP-27S - jebem - 06-28-2014, 04:44 PM
RE: I was bored and found a HP-27S - jebem - 06-28-2014, 05:37 PM
HP-27S that does not turn on - franz.b - 11-06-2020, 08:24 PM
RE: I was bored and found a HP-27S - jebem - 11-09-2020, 07:14 AM



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