Valentin Albillo's HP Collection

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HP Calculator Vintage Letters

This Section features scans I've made of selected letters I exchanged with a number of HP-calc fans mainly from 1979 to 1981 and a few beyond. All are part of my Project HAM and due to their perceived historic worthiness I'm making them available here for the very first time.

I scanned most letters at 300 dpi, resulting in hi-res 2,552 x 3,508 PNG images, which were then converted to multi-page PDF documents with embedded OCR'd texts when possible (e.g.: to allow for copy/paste operations). Some of them also include text pages with my own Notes, providing background info and extra details.

PDF HP Letter 1977-05-01 - Letters from HP UPLE to Fernando del Rey (Full Scan)

(14 pages)

Various letters sent by the Hewlett-Packard Users' Club Europe to Fernando del Rey when he asked for info about the club in order to subscribe to it (I got the same letters, these are his).

It includes one typical envelope, Member Rules and Regulations, Program Orders and Program Submittals conditions, Payment conditions, announcing the first & second European Updates to the Users Library Catalogue, announcing a questionnaire and the latest Key Notes edition V2N1, the April 78 Catalogue Update (547 new programs), the Users' Club BLUE and GOLD MEMBER CARDS, the European Users' Library becoming multilingual and offering recorded magnetic cards, a Membership Renewal Notice and a Thanks Note for renewing, three different models of Program Order Form-Invoice sheets, and a Shipping Label Form.

Hopefully this will allow today's users to get an idea of just how dynamic and exciting was to own an HP-67, HP-97 or HP-41C calculator back then, and how deeply was HP committed to their advanced calculators and users.

PDF HP Letter 1978-07-31 - Letter from Valentin Albillo to HP UPLE (Full Scan)

I had subscribed earlier to the HP UPLE (HP Users' Programs Library Europe) but once it expired I failed to renew my subscription and HP Europe promptly sent me a letter (which regrettably seems to be lost) asking me for the reasons I had not to renew.

The present letter is my reply to them [...] Includes Notes.

PDF HP Letter 1979-12-01 - Letter from Valentin Albillo to John McGechie (Full Scan)

(3 pages, includes Notes)

This is the very first letter I wrote back in 1979 to John McGechie (Australian PPC Melbourne Chapter) when I was a very young adult and still at High School.

At the time, I was but a fledgling HP-calc user with rudimentary self-taught English, but already bitten to the core by the HP bug. Includes Notes

PDF HP Letter 1979-12-10 - Letter from Valentin Albillo to PPC (Full Scan)

This is the very first letter I sent to PPC back in 1979 asking to join the Club [...] I was absolutely ecstatic at discovering PPC CJ and wanted to be a part of it ASAP, thus this enthusiastic letter [...]

This is how it all began. Includes Notes.

PDF HP Letter 1979-12-19 - Letter from John McGechie to Valentin Albillo (Full Scan)

(7 pages, includes Notes)

This was John McGechie's handwritten 6-page reply to my very first letter to him, where I unashamedly asked him zillions of questions, as an interested but total newcomer to the 1979 HP calc scene was bound to do.

He answered most of them and encouraged me to join PPC for further tons of information, which I promply did. Includes Notes

PDF HP Letter 1979-12-22 - Letter from PPC to Valentin Albillo (Full Scan)

This is PPC's reply to my 1979-12-10 letter asking to join the Club, once I sent the required money for a one-year subscription. PPC duly processed it and I was assigned PPC Member Number #4747, a nice number which I very much liked.

My initial subscription ran from January 1980 to December 1980, and it was renewed exactly once. While it lasted I [...] Includes Notes.

PDF HP Letter 1980-01-15 - Letter from Valentin Albillo to William Wickes (Full Scan)

This is my first letter to William C. Wickes, of 41 Synthetics (and later RPL) fame, sent just after I joined PPC (Jan 1980), thus becoming Member #4747.

At the time I was very keen in contacting relevant people mentioned there, to try and get hold of all the marvels I saw announced in the pages of PPC CJ, such as [...] Includes Notes.

PDF HP Letter 1980-02-01 - Letter from Valentin Albillo to Michael Tarnowski (Full Scan)

This is my reply to Michael Tarnowski, who back in 1980 wrote a letter to me (alas, probably lost) with a number of questions about my program "52206 A Chess Game" for the HP-67, which I had earlier submitted to the HP Users' Program Library Europe. Includes Notes.

PDF HP Letter 1980-03-18 - Letter from Michael Tarnowski to Valentin Albillo (Full Scan)

This is Michael Tarnowski's (Germany) reply to my letter dated 1980-02-01, in which I explained in detail the internal logic my "52206 A Chess Game" HP-67 program used to make its moves and win the game.

As seen in my next letter to him, dated 1980-04-01, I did my best to comply with his requests and actually much more. Includes Notes.

PDF HP Letter 1980-04-01 - Letter from Valentin Albillo to Michael Tarnowski (Full Scan)

This is my second letter to Michael Tarnowski, who formerly was interested in the logic used by my program "52206 A Chess Game" for the HP-67 (submitted by me to the HP Users' Program Library Europe), so I sent him a first letter providing the information he asked for, [...]

Additionally, I took the opportunity to inform Mr. Tarnowski about PPC, including a very detailed primer on HP-41C synthetics and their uses, and attaching to my letter photocopies of a number of relevant articles about synthetics. I also included a list with 160 UPLE HP-67 programs I owned [...]. Includes Notes.

PDF HP Letter 1980-06-07 - Carta de Felipe Landa a Valentin Albillo (Full Scan)

(in Spanish, includes Notes in English)

This letter was sent to me by D. Felipe Landa in reply to a letter I previously sent him (now sadly lost) after I saw his name in the UPLE Catalog as the author of a number of quite interesting programs submitted by him to the HP UPLE (Hewlett-Packard's Users' Program Library Europe), to which I was subscribed at the time and had also submitted many programs as well. Includes Notes in English.

PDF HP Letter 1980-06-14 - Carta de Valentin Albillo a Felipe Landa (Full Scan)

(in Spanish, includes Notes in English)

This is my reply to a letter sent by D. Felipe Landa a week earlier (see 1980-06-07 - Carta de Felipe Landa a Valentin Albillo.pdf), in which he kindly offered to directly send me any number of his HP-67 programs submitted by him to the HP UPLE, and also commenting that in time he got quite disillusioned when ordering UPLE programs with highly suggestive titles and abstracts but ultimately very disappointing. Includes Notes in English.

PDF HP Letter 1980-06-30 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

This 7-page letter is one of the first I sent to Richard Nelson, who was in charge of PPC back then. I wrote many others once my PPC subscription started for good in January 1980 (about one letter per month, sometimes two) but this is the earliest survivor [...] and included 6 pages with my newest contributions to the ongoing PPC ROM Project and other PPC Journal regular sections, namely:

  1. Several routines for the PPC Custom ROM : an improvement to the Block exchange routine, flag 55 toggle & block revert routines, a set of 67/97 conversion routines for people without the expensive card reader, including P<>S, CLREG, RCLΣ, FIX, SCI, ENG, ISZ, DSZ, ISZI and DSZI.

  2. Several inputs for NOP : a bug in the card reader ROM, a possible bug in the PACK function and the odd behaviour of editing functions when applied to multi-alpha-label programs.

  3. Three inputs to BITS & PIECES : two simple routines, which avoid reinventing the wheel, and a Computer challenge. This one is tremendously tricky.

  4. An article about Synthetic Programming Techniques. The techniques discussed are new to most PPC members and have never been previously mentioned in the Journal explicitly. They are:

    (a) Any NNN as a line in a program (uses synthetic texts.)
    (b) Constants as lines in programs : it shows how to save up to 6 bytes per constant (7 if more than one), and reduce digit entry time by 5x.
    (c) Non-stack set up of indexes : shows how to quickly initialize up to 3 indexes for indirect use of up to 3 registers without disturbing the stack.
Includes Notes.

PDF HP Letter 1980-07-10 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

This 5-page letter is also one of the first I sent to Richard Nelson, who was in charge of PPC back then. In this letter I focused mainly on various aspects of the PPC ROM Project logistics. I also included a couple of additional contributions for the ROM, namely:

I also included an input providing a list with names and functionalities for some 50 "Flag 30 Catalog" functions, giving the actual function being executed upon filling up their prompts (digits, alpha, IND, stack, etc.), which featured such gems as eG0BEEP and $T+N IA, allowing programming printer functions without a printer, all 127 local labels, etc. Includes Notes.

PDF HP Letter 1980-07-15 - Letter from Valentin Albillo to John McGechie (Full Scan)

This is my 3-page second letter to John McGechie, of the Australian PPC Melbourne Chapter, who previously had most kindly replied to my first batch of a zillion questions in a very comprehensive, handwritten multi-page letter where he strived to answer them all as best he could.

After a several-month hiatus and having joined PPC as he suggested in his reply, I took the opportunity to contact him again and show him my progression from "utterly clueless newbie" to "accomplished knowledgeable member" (or something like that), though that wouldn't save him from still more questions and some private comments.

Among the matters I discuss in this second letter, there's a report on my attempt to create a CP (Clear All Programs) synthetics-based routine for the PPC ROM, which features my tentative code, [...] Includes Notes.

PDF HP Letter 1980-07-20 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(19 pages, includes Notes)

This 18-page letter is one of the longest I sent to Richard Nelson [...] The letter also included a treasure trove of additional new materials submitted for publication in the PPC Journal, among them:

  1. An updated version of my Black Box programs featuring extra functionalities,
  2. My solution to a Computer Challenge issued by John Kennedy,
  3. The shortest & fastest random number generator routine for the HP-67/97/41C (perfectly adequate for games),
  4. Several inputs for the NOP and Feedback columns,
  5. Two inputs for the ROM Progress column, including my Display Test synthetic routine,
  6. A full 3-page article "STO b, RCL b or The Universal Byte-Jumper" showing how to use just those two synthetic instructions to easily create any synthetic function, text or key assignment, how to unrestrictedly jump to anywhere in memory, and how to break PRIVATE, with full documentation and examples
  7. A 5-page, complex HP-67/97 two-card program to design Elliptic Lowpass Filters, and
  8. An HP-25/25C/33E/C program to numerically solve a given 2nd-order differential equation of the form y" = f(x,y) using a 5th-order method while taking just 37 program steps.

... among other things.

PDF HP Letter 1980-08-01 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(10 pages, includes Notes)

At this time I was still very enthusiastic about anything and everything having to do with HP calcs programming (mostly with the new HP-41C and its awesome synthetic instructions,) so I was creating and submitting materials to Richard Nelson for publication in the PPC Calculator Journal in rapid-fire style, [...] The letter also included two significant contributions, namely:

  1. A synthetic routine for the PPC ROM, namely Clear (all) Assignments, which had been requested by several members because of its obvious usefulness (and it wasn't included, of course), and
  2. The very first version for any machine of my Othello program, which was a long, optimized, polished program which would play quite fast a non-trivial game against the user, optionally printing a nice labeled board if a printer was available. [...]

PDF HP Letter 1980-08-05 - Letter from John McGechie to Valentin Albillo (Full Scan)

This 26-page (!) handwritten letter is Melbourne PPC Chapter's John McGechie's reply to my previous letter to him dated 1980-07-15. John's handwriting takes some effort to decipher at times, but it's totally worth it.

He begins with some very detailed comments (several pages in fact !) about my attempt to create a CP (Clear all Programs) synthetics-based routine for the PPC ROM, including a number of suggestions on how to successfully implement it using his own b2 routine. He then discusses in great detail the various types of END and .END., and his attempts to create a RAM test to check their locally-created double-density RAM modules. Includes Notes.

PDF HP Letter 1980-08-12 - Letter from Valentin Albillo to John McGechie (Full Scan)

This 6-page letter is my reply to the 26-page handwritten letter that Melbourne PPC Chapter's John McGechie sent to me dated 1980-08-05. [...] I expressed my appreciation for his comments and suggestions about my CP (Clear all Programs) synthetic routine, and my intention to experiment with the .END. to make it work.

I also included a short but detailed analysis of CP, explaining what it did and how, and much more, such as synthetic trivia, numeric built-in functions which can return alpha data (!), my own sleuthing re "ghost" functions, useful tips and hints, the works ! Includes Notes.

PDF HP Letter 1980-08-15 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(7 pages, includes Notes)

This 6-page letter is the fourth of several letters I sent in quick succession to Richard Nelson including both comments/questions and new materials created by me for publication in the PPC Calculator Journal, [...]

I included several new materials within this letter, namely a very complete table of "ghost" (flag 30 catalogs) functions, documenting some 70 of them, which included their names, the parameters needed for easily generating them using the famed John McGechie's KA program, the actual functions executed for all kinds of inputs to their prompts (digits, alpha, IND, stack, IND stack) and pertinent notes detailing the finer points (for instance the use of status register Q to easily generate non-standard labels) and any caveats, all in all a most useful TTT (True Treasure Trove).

Additionally, I also included two inputs for the PPC ROM, consisting in:

  1. A short and so far the fastest routine to find the address of the first statistic register, as well as the absolute addresses of the statistics block, the curtain (R000) and the final .END., thus completely decoding the contents of the tricky c status register, and

  2. Another short routine, this time a 15-line utility to help in loading into program memory any XROM instruction without the module or peripheral being plugged in.

PDF HP Letter 1980-09-01 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(11 pages, includes Notes)

I sent this 10-page letter to Richard Nelson [...] the letter includes a number of my materials, all of them intended for publication in the PPC Calculator Journal, namely:

  1. RF, a short but very capable & fast general root finder routine for the HP-41C, which features an interactive prompting version (RF) as well as a non-prompting one (RPF) callable from user's programs [...]

  2. A Chess playing program for the HP-67 which allows the user to play chess vs. the HP-67. The user conducts the Black king vs. the whole White army conducted by the HP-67. If the program manages to give checkmate in 6 moves or less [...]

  3. T, a revision of the Arithmetic Teacher program featured in the Standard Applications Pac included with every HP-41C. My revision works the same as the original but it's 120 lines/32 registers (vs. 163/52) so it saves as many as 20 registers [...]

  4. Inputs to the FEEDBACK, 41C NOTES and/or ROUTINES sections, including my various optimizations and corrections to [...]

  5. A PROGRAMMING TIP showing in full detail how to very easily create on the fly a program line containing any arbitrary text (synthetic characters and all) using just STO b and RCL b [...]
Finally, I comment on the proposed inclusion in the PPC ROM of [...].

PDF HP Letter 1980-09-19 - Letter from Tony Collinson to Valentin Albillo (Full Scan)

This letter was sent to me by Tony Collinson, at the time a fairly new member (#5491) of PPC who (apparently) seemed to work at the local HP premises, judging by the envelope, [...]

As it happened, some time ago I had submitted to Richard Nelson an article including how to very easily defeat PRIVATE [...] Mr. Nelson censored out that part of the article, so a number of interested members noticed the fact and wrote directly to me asking for the details. Mr. Collinson's was one of those letters and I promptly sent him the censored part [...]. Includes Notes.

PDF HP Letter 1980-09-21 - Letter from HP UPLE to Valentin Albillo (Full Scan)

(13 pages, includes Notes)

This letter was sent to me from Geneva (Switzerland) by the Users' Program Library Europe per my previous request for information. It included a 4-page leaflet with very detailed info about the UPLE, namely: [...]

Additionally, upon subscribing you'd also get a free subscription to "Key Notes", as well as 4 program coupons for you to choose as many programs from the Library, which was actually the countervalue of the subscription fee so essentially you'd get one or the other for free. The letter also included: • the full 7-page documentation for a very nice sample program, Simon (from the Number and Word Games category), also [...]

PDF HP Letter 1980-09-25 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(11 pages, includes Notes)

I sent this letter to Richard Nelson including within the following materials for their publication in the PPC Calculator Journal, namely:

  1. BASIC Software for the HP-41C, an article describing some guidelines to convert an arbitrary BASIC program to the HP-41C's RPN version in a rather automatic way, [...] An enclosed example demonstrated in full the complete translation process applied to an autolearning BASIC game, "Even Wins", [...]

  2. RP (Roots of Polynomials), an HP-41C program to automatically find all real and/or complex roots of a polynomial equation of arbitrary degree with real and/or complex coefficients, in a completely global fashion (i.e., no initial approximations required) and callable as a subroutine from other programs.

Finally, I commented on the proposed publication of the PPC Barcode Book and the wand itself, and some notes on [...].

PDF HP Letter 1980-09-27 - Letter from Valentin Albillo to John McGechie (Full Scan)

(10 pages, includes Notes)

I sent this letter to John McGechie to thank him and the members of the PPC Melbourne Chapter for their extremely warm welcome and enthusiastic reception of my materials. The letter continues with comments re the PPC Jul/Aug issue's materials, as well as comments on the materials selected (or not) for the PPC ROM. Additionally, I also comment on the article I sent to PPC which was censored because of PRIVATE, and I include and detail my own attempt to improve on John's b2 synthetic routine.

Finally, I include the following materials:

  1. RP, an HP-41C program to automatically find all roots of a polynomial equation of arbitrary degree (limited only by available memory) with real and/or complex coefficients, in a completely global fashion (i.e., no initial approximations required) and callable as a subroutine from other programs,

  2. an HP-41C fast implementation of an N-level RPN stack, including all the usual functions, with N limited only by available memory,

  3. an autolearning HP-41C game, "Even Wins", which plays better and better the more you play against it.

Last, I mention my programs to be submitted next to the Melbourne Chapter, including least-squares N-variable linear regression or Nth-degree polynomial regression, NxN-matrix 2-level RPN stack with the usual matrix operations built-in, plus Checkers and Chess 5x5 coming soon.

PDF HP Letter 1980-10-09 - Letter from John McGechie to Hugh Kenner (Full Scan)

(11 pages, includes Notes)

Back in 1981, nearly 41 years ago as of 2022, the Wall Street Journal launched a spin-off project called the Wall Street Journal Magazine, and commissioned a number of people to write articles for it. One of them was Hugh Kenner, [...] Hugh thought about it and decided to focus his commissioned article on the amazingly unexpected applications that HP-41C owners were developing for it, [...] Hugh titled his finished article "Calcunuts" and to my delight, among the many interesting people and their creations, it includes references to me and my Othello program at several places [...]

In order to best create the article, Hugh sent letters featuring a number of relevant questions to several authors [...] and one of those people was John McGechie, of PPC Melbourne Chapter's fame and my unofficial "mentor", who was one of the pioneers in 41C synthetics [...] John did comply and sent a huge letter to Hugh, the one featured here, [...] Hugh took good note of what John wrote, and also mentioned him in the WSJM article [...]

In his 9-page typewritten reply to Hugh's questions [...] [John] goes on to describe in extensive detail his experiences with and his thoughts about these wonderful machines [...] all of it described by him as a meaningful intellectual and philosophical endeavour, delightfully adorned with his own personal experiences and nice tidbits of his life. Matter of fact, it includes what can be considered a short biography enriched with his own personal reflections, [...] May he rest in peace.

PDF HP Letter 1980-10-15 - Letter from John McGechie to Valentin Albillo (Full Scan)

(7 pages, includes Notes)

This letter was sent to me by John McGechie in reply to my previous letter to him. He mentions the very positive reaction of local members to my recently submitted materials, then he discusses the Synthetic Routines for the PPC ROM listing which he received, the CKA and AN routines in particular, [...]

He enclosed letters from himself, Mr. Nelson, and a third person about the PRIVATE feature, asking for my opinion [...] he also included a new Stack & Alpha Analysis Form and new routines for his WP (Word Processor) project, dealing with slicing and right- and left-hand justifiers. Next, he mentions how his b2 routine could be improved, as well as a new method to read out microcode [...] and that Hugh Kenner (Prof. of English at Johns Hopkins Univ.) wrote asking him why the in/sane obsession with PPC programming (Hugh was preparing his wonderful article "Calcunuts" commissioned by the Wall Street Journal Magazine; see John's 9-page reply to Hugh)

PDF HP Letter 1980-10-16 - Letter from Valentin Albillo to John McGechie (Full Scan)

(17 pages, includes Notes)

I wrote this letter to John McGechie commenting on the recently released TRS-80 Pocket Computer (a rebranding of the original SHARP PC-1211, the very first pocket computer), and giving him a number of scoops, [...]

A 2-page post-data follows. featuring additional comments on assorted things, including details of my Othello program's internals and a tirade on the still-unfinished PPC ROM [...] Finally, I include the following 4 articles for the HP-41C:

  1. Technical Subjects, a 3-page discussion on long synthetic labels (say, LBL "HEWLETT-PACKARD" ) and their behavior [...] I also discuss three weird synthetic assignments and some worthwhile uses for them, including another new way to break PRIVATE,

  2. MR, NxN Matrix Operations, a 5-page article including a program to perform individual or chained NxN matrix operations using a 2-level RPN stack, with N limited only by available memory [...],

  3. 3D-PLOT, a 3-page article which features a program which can plot a user-defined function in such a way that the resulting plot seems almost 3D, [...] It provides 5 parameters to fine-tune for the best results.

  4. Graphic Dice, a very short and fast synthetic subroutine to accumulate into the printer buffer the graphic representation of the face of a die given as input the number of pips. [...]

PDF HP Letter 1980-10-20 - Letter from Tony Collinson to Valentin Albillo (Full Scan)

Previously, Tony Collinson, another PPC member (#5491), had sent me a letter requesting the details on how to defeat PRIVATE, which I had documented in an article submitted to Richard Nelson for publication in the PPC Calculator Journal, but which suffered heavy censorship.

I promptly fulfilled his request by sending him (and another dozen people requesting the same information) the censored parts of the article, and about a month later he sent me the present second letter, in which he thanked me for it, among other assorted comments on the matter. Includes Notes.

PDF HP Letter 1980-12-12 - Letter from Valentin Albillo to John McGechie (Full Scan)

(25 pages, includes Notes)

I sent this 24-page letter to John McGechie [...] including extensive comments on my HP-related activities, the recently arrived PPC Technical Notes issues 3 & 4, the PPC Calculator Journal October & November issues and some HP-41C microcode notes sent by Tom Cadwallader, plus [...]

Next, I comment on an interesting letter from Mr. Wickes and John's reply, focusing on the huge differences between [...] , I comment on the proposed PPC ROM, which I considered likely to be obsoleted soon by powerful HP models just about to be released, and [...] some ideas for the HP-41 to be able to survive vs. new rumoured models such as [...] Finally I include the following materials [...] for their possible publication in the Melbourne Chapter's Technical Notes magazine, namely:

  1. A (french) article from L'Ordinateur Individuel describing in detail how to interface an EPROM to a TI-57/58 calculator, which could likely be adapted to work with HP calculators as well.

  2. The first 9 pages of the English section of the User's Library Europe [...]

  3. A version of my HP-41 Othello program converted to run on the HP-85 computer [...]

  4. MLR, a Multiple Linear/polynomial Regression HP-41 program I wrote, which given a set of data can compute (in the least-squares sense) the coefficients of either a linear regression in N independent variables or else the Nth-degree polynomial regression [...]

  5. CHKERS, Checkers 3.0, another complex HP-41 game program I wrote which can play Checkers vs. the user [...]

  6. VAL, a small routine which is the "inverse" of ARCL, as it takes numeric data stored as text in the Alpha register and converts them to numeric data proper in the X register [...]
[...] the package also included (and extensively commented on) the HP-34C Matematica Avanzada Solutions Book commissioned by HP Spain for the local market [...] You can download this 78-page PDF book [...]

PDF HP Letter 1981-04-10 - Letter from Valentin Albillo to John McGechie (Full Scan)

(18 pages, includes Notes)

I sent this 17-page letter to John McGechie just a couple of months before my departure to comply with my mandatory Military Service [...] The letter begins with me telling him about my many activities and among them my attempt to create a Madrid Chapter of PPC [...] I then told him about the various people who'd sent me letters (Jakub Tatarkiewicz, Keith Jarett, Tom Cadwallader, John Dearing, etc.) and what they told me in them [...]

Next, I comment on a number of HP products rumoured to be released soon, including details on the [...] so the rumours I heard were correct for the most part. Now there follows a 6-page section where I comment very extensively and enthusiastically on the newly released SHARP PC-1211 Pocket Computer, with full details and many comparisons vs. the HP-41 [...] Finally I include the following materials for their possible publication[...] namely:

  1. O2, a new version of Othello featuring 2 levels of play, Level 1 playing exactly the same as my original Othello program, and Level 2 featuring better play at the expense of slower running times [...]

  2. SEED, a quasi-truly random number generator (RNG), which takes no input and generates a seed (0 <= seed < 1) to be used to initialize another RNG, thus no need to ask the user for an initial seed [...]

PDF HP Letter 1981-05-15 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(14 pages, includes Notes)

I sent this 13-page letter to Richard Nelson in order to submit as many of my materials as possible before I left home for many months [...] I proceeded to describe the new ones attached to this letter, namely:

  1. A very short and fast NxN Matrix Inversion program for the HP-41C, able to invert square matrices from 1x1 up to 16x16 (256 elements) in [...]

  2. A Fourier Series - Harmonic Analysis program for the HP-41, which is the much more capable version (up to 141 harmonics at a time and 2x-3x faster) of the same program for the HP-67 [...]

  3. A Fourier Series - Harmonic Analysis program for the HP-67, able to quickly compute and store up to 10 harmonics at a time, while also computing the sum of squared errors and allowing the computation of projections for any given x, plus an automatic sweep capability.

  4. A Function Integration (FI) subroutine & driver, submitted for its possible inclusion in the PPC ROM [...] It's the shortest and fastest such routine, based on the 3-point Gauss-Seidel quadrature formula and thus providing 5th-order accuracy using just 3 function evaluations per subinterval [...] includes a short program which programmatically calls this routine to compute the volume of a given solid of revolution.
An extended discussion on the defeating of the HP-41's PRIVATE feature follows and I include in the letter proper my own method to defeat it based on using the synthethic pair STO/RCL b [...]

PDF HP Letter 1981-06-13 - Letter from Valentin Albillo to Richard Nelson (Full Scan)

(9 pages, includes Notes)

This 8-page letter is one of the very last letters I sent to Richard Nelson before I went abroad [...] As this present letter was essentially the last one where I would "talk" to Mr. Nelson (one-way communication, as always) I threw "political correction" aside and went into mild "rant mode", giving him a piece of my mind for the last time [...] Anyway, I didn't care for or expect an answer (there was none, of course) as I was going to leave it all behind immediately.

Just for the sake of it, I also included one last contribution for its possible publication in Mr. Nelson's PPC Calculator Journal, namely my Chess 5x5 program for the HP-41C. Actually, I didn't care in the least whether it would be eventually published there or not, as PPC CJ was the last place I submitted it to: I had already submitted it to Melbourne Chapter's Technical Notes and both the US and Europe HP Users' Libraries for good, and all of them featured it (and also included it in the "Hewlett-Packard HP-41 Users' Library Solutions" Games II book !!) [...]

End of an age for me.

COPYRIGHT NOTICE
These articles, programs, pictures, their descriptions and other materials created by me are (c) Valentin Albillo, and can be used freely for non-profit purposes as long as (1) the contents aren't modified in any way and (2) the copyright is acknowledged. In plain words, you can download them and use them for non-profit purposes but do not include them in any media and/or site for which you're asking money, do not tamper with their contents and do not say or imply that you created them or that you don't know who created them, you must always give due credit to me.