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(04-17-2020 08:40 PM)BobVA Wrote: [ -> ]My sentimental favorite would the still-perfectly-working HP-15C I bought for grad school in '84. It saw a lot of use and never let me down, or even asked for a battery change.

But on my desk is an HP-25LE. It's not the same '25 that got me through college, but what it lacks in provenance it more than makes up for by doing everything I need doing these days (printing, alarm clock, continuous memory, basic engineering functions). And I think it's the coolest looking calculator HP ever made. It went from futuristic to retro-tacular with no stop at "dated." :-)
Excuse me, what do you mean for HP-25LE? limited edition? i never heard about it....maybe you meant HP15 LE Smile
(04-17-2020 09:16 PM)aurelio Wrote: [ -> ]Excuse me, what do you mean for HP-25LE? limited edition? i never heard about it....maybe you meant HP15 LE Smile

Oops! I meant HP-25LP :-)

(Panamatik's fantastic upgrade for the Woodstock series)
First, because it was my first HP is the 25. Which is now an HP 25IR/GPS.

Second my original tall keys 41C which is now a 41CL tall keys, and crunched my data for my MSc.

Third, my first restoration and subject of a DATAFILE, HP 65 fully restored.

Fourth my 67.

And fifth because it is so capable is my HP 29LP (Panamatik) used at work when I am not Beta testing the DM42 or the DM41X

... the HP 01 cause it is so cool

And back to the 41CL tall keys which will be set up when COVID is over with HPIL to get me through my PhD. Now that will be cool, HPIL in a lab at Simon Fraser University in 2020. Might have to document that for a future HHC.

So many and so little time.
(04-18-2020 04:28 AM)Geoff Quickfall Wrote: [ -> ]Now that will be cool, HPIL in a lab at Simon Fraser University in 2020. Might have to document that for a future HHC.

Please do!
My dad’s mint condition HP 35, received June 1973 (does anyone know how to obtain a battery pack for the 35?)...works perfectly on it’s power cord, have it’s original leather pouch, plastic shipping box. Also, an HP 42s given to me by an exceptionally generous individual. Absolutely most missed is my HP 67 and it’s magnetic cards. I have no idea what I did with it.
On the auction site search for HP classic battery pack.
This is a hard one.

I still have my original HP-41C. One of the early ones with gold contacts and, I think it was a "bug 3" machine IIRC. I made the switch from a TI-58 and never looked back. I've since picked up a CV and CX and many of the peripherals.

But, while nowhere near as capable, I still love the feel of the HP-29C. And, the HP-15C which was amazing. My original HP-15C was stolen, but I picked one up as well as the LE version since.

The HP-16C was so unique. I developed a fast integer square root algorithm using it.

I guess I'd have to say my original HP-41C. Not used as much as the others now however..
(04-18-2020 04:28 AM)Geoff Quickfall Wrote: [ -> ]And back to the 41CL tall keys which will be set up when COVID is over with HPIL to get me through my PhD. Now that will be cool, HPIL in a lab at Simon Fraser University in 2020.

You may be the most educated pilot in Air Canada's fleet!?

What are you studying?

What are the load factors in Vancouver-Sydney these days?
Hi Dave

Schedule is 25% of pre COVID. Mostly domestic except for freighter operations for emergency supplies with converted 777 and 787s. Also repatriation flights. Some foreign destinations which were daily and now biweekly.

Sydney, Melbourne and Brisbane all cancelled.

Looks like most of the summer off, one flight per month. So lots of time for the BOOK and other stuff. Looks like PhD is now postponed to September when the whole world should have more of a handle on the current crisis.

PhD in Paleo-Climatolgy. And extension of my MSc of which I presented a minor portion at HHC2014:

Palynology and my HP 41C & CX
(04-19-2020 02:11 AM)Geoff Quickfall Wrote: [ -> ]So lots of time for the BOOK and other stuff.


(04-17-2020 02:44 PM)Nihotte(lma) Wrote: [ -> ]what to think of a calculator without dedicated index register, indirect arithmetic possibility and so on...

Actually, the 12c does have indirect addressing, via the N register and STO/RCL cfj and nj. You have to be careful about using it for this purpose, but it certainly is possible and it does work. I used that capability in my prime factorization program for the 12c.
Hi, Nihotte(lma):

(04-17-2020 02:44 PM)Nihotte(lma) Wrote: [ -> ]I think it's my second-hand (original) HP12C, in fine. [...] For a scientific or a computer scientist, what to think of a calculator without dedicated index register, indirect arithmetic possibility and so on...

There's a way to use the many storage registers indirectly, as shown in my article (PDF document, click the link to read it and/or download it):

HP-12C Serendipitous Solver
  • 8-page article for the HP-12C financial calculator, includes a 37-step program which makes use of the built-in microcode IRR solver and a number of assorted financial functions to find one or more real roots of polynomials up to the 14th-degree (and up to 1480th-degree or more if there are groups of repeated coefficients). The program allows for quickly entering groups of repeated coefficients and correcting wrong inputs on the fly, and can also evaluate the polynomial for any given arguments.
    Both root finding and polynomial evaluation are implemented using built-in financial functions without user-code loops or branching, so it's the fastest and more convenient polynomial root solver for the whole Voyager Series calculators, surpassing even the HP-15C's SOLVE function in this regard. Frankly, one of my very best programs for any calculator and among the ones I'm proud of the most.
    The program is fully commented on a step-by-step basis and 5 sample worked cases are included, among them finding real roots of polynomial equations of degrees 3, 7 and 137, and all 5 real roots of a 5th-degree equation.
Other articles of mine related to the HP-12C that perfectly demonstrate its "scientific capabilites" (and even "gaming"), and which you might like, are the following:

HP-12C Tried and Tricky Trigonometrics
  • 10-page article, includes a crafty 99-step program for the original HP-12 financial calculator which evaluates all six standard trigonometric functions (Sin, Cos, Tan and their respective inverses) very quickly and with full accuracy over an extended range of arguments.

Long Live the HP-12C
  • 6-page article celebrating the best-selling HP-12C, includes a 72-step program which will allow your HP-12C to play a challenging game of "Bridge-It!" against a human opponent in boards of any size up to 99x99. Try it on your unsuspecting financially-minded friends and see how they fare against the HP-12C !
(04-18-2020 04:28 AM)Geoff Quickfall Wrote: [ -> ]And back to the 41CL tall keys which will be set up when COVID is over with HPIL to get me through my PhD. Now that will be cool, HPIL in a lab at Simon Fraser University in 2020. Might have to document that for a future HHC.

In which field and on which topic will you write your PhD thesis?
Hello Jurgen

Paleo climatology based on palynlomorphs, that is I am a Paleo Climatologist Palynologist which means I use microfossil records to add to past climate data.

Slightly off topic, but one of the reasons for my love of the 41C/CX. I worked as a commercial ‘bush‘ pilot flying float aircraft in northern Canada. That salary allowed me to replace my aging HP 25C and purchase my first HP 41C in 1980. I completed my Botany degree while still flying and that morphed into an MSc. The research grant purchased us a brand new 8088 with two stacked 5mb hard drives and a monochrome Amdek screen.

The lab including fume hood, desiccators and ovens were on timers based on the time functions in the HP 41CX, which controlled 4 different lab pieces of equipment via HPIL. My math and number crunching was via the HP 41CX routines I composed. I had an HPIL printer paper and a tape drive back up for data.

For an informal taste and some of the HP 41C/CX involvement in the MSc check out my HHC2016 presentation on YouTube.

My PhD application required a two page proposal. This is unlike the full proposal as it is not in depth and only gives a cursory direction. The formal proposal occurs after acceptance and involves the PhD committee usually within six months of the research start.

Statement of Proposal


My MSc research (Quickfall, 1987) reconstructed the successional history of three bog sites on Haida Gwaii; Argonaut Hill, Drizzle Pit and Kunghit Island K3. The conclusion of the research indicated that peat growth and spread (paludification) could be divided into two episodes centered around 4700 yBP (5400 cal yBP) and 2500 yBP (2500 cal yBP).

Drizzle Pit Bog, Geike Bog and Kunghit Island bogs formed approximately 4860, 4620 and 5330 cal yBP respectively; probably in response to reduced temperatures and/or increased precipitation. This is also indicated by a synchronous recurrence surface at Argonaut Hill. This possibly concurrent event, coincides with numerous studies in Europe and North America (Cruise, G.M. 1990; Anderson et.al. 1994).

With respect to the above events, there is a paucity of high-resolution data for Haida Gwaii as well as western Canada. Haida Gwaii offers a unique benefit with respect to anthropomorphic induced paludification and succession. Studies in Europe, with its continuous history of manipulation of the environment by man, leads to increased complexity as to the changes in plant/bog succession (Cruise, G.M. 1990). Haida Gwaii offers many bog sites with a non-industrialized environmental history of the mid-to late Holocene. Interestingly there is a climatic change event known as the “4.2 ka BP climatic event” (Weiss, H., 2016). This paper focuses on Europe, Asia and the Mediterranean and discuss the 4.2 ka BP event and its dramatic consequences for human civilizations, but comparative data are lacking for the Pacific Northwest.

There are however reports of alpine glacial advances around 4.2 ka BP climatic event (Menounos et. al., 2008). Some evidence points to an advance as early as 4.9 and 4.2 ka BP (Gardner and Jones, 1985, Koch et. al., 2007, Osborn et. al., 2007, Lenard et. al., 1999). One paper indicates a series of climatic events causing “long periods of extended ice cover date to about 6.9-5.6 ka, 4.9-3.8 ka, 3.5-1.9 ka (Clague et al, 2009). 


From the papers noted above, and from my preliminary evidence in 1987 on bog ecosystems from Haida Gwaii, that climatic changes have occurred and that these changes sometimes coincide with glacial advances in British Columbia.

It is proposed that a high-resolution analysis of Holocene paludification events on Haida Gwaii as originally noted in my 1987 thesis be undertaken. The high-resolution analysis will include detailed paleoecological analysis of several peat cores using ecologically sensitive biological indicators such as rhizopoda, fungi, testate amoeba and other fossils in addition to pollen and spores (Kuhry et.al. 1992, Mitchell et.al. 2008; Booth et.al. 2010).

Concurrently, the use of high precision radiocarbon analysis will increase the level of accuracy for estimation of changes in the rates of peat accumulation (Blackford, 2000). This research will lead to a more detailed reconstruction of climate changes that occurred on Haida Gwaii that involve paludification, bog growth and carbon sequestration during the mid to late Holocene. The key focus of this study is to produce a more detailed paleoecological record than has been available previously on the west coast of British Columbia, for comparison with recent high-resolution international records.


Anderson, R.S., Smith, S., (1994). Paleoclimatic interpretations of meadow sediment and pollen stratigraphies from California. Geology, vol. 22, pp 723–726.

Booth, P.K., Lamentowicz, M., Charam, D.J. (2010). Preparation and analysis of Testate amoebae in Peatlands. Mires and Peat, vol. 7, pp 1-7.

Blackford, J., (2000). Paleaoclimatic records from peat bogs. Tree, vol. 5, pp 193–198.

Clague, J.J., Menounos, B., Osborn, G., Luckman, B.H., Koch, K., (2009). Nomenclature and resolution in Holocene glacial chronologies. Quaternary Science Reviews, vol. 28, pp 2231–2238.

Cruise, G.M. (1990). Holocene peat initiation in the Ligurian Apennines, Northern Italy. Review of Paleobotany and Palynology, vol. 63, pp 173-182.

Koch, J., Osborn, G.D., and Clague, J.J. (2007). Pre-“Little Ice Age” glacier fluctuations in Garibaldi Provincial Park, Coast Mountains, British Columbia, Canada. Holocene, vol. 17, pp 1069-1078.

Kuhry, P., Gignac, L.D., and Vitt, D.H. and Bayley, S.E. (1992). Development of Sphagnum-dominated peatlands in boreal Canada. Canadian Journal of Botany, vol. 71, pp 10–22.

Leonard, E.M., and Reasoner, M.A. (1999). A Continuous Holocene Glacial Record Inferred from Proglacial Lake Sediments in Banff National Park, Alberta, Canada. Quaternary Research, vol. 51, issue 1, pp 1-13.

Menounos, B, Clague, J.J., Osborn, G., Luckman, B.H., Lakeman, T.R., and Minkus, R. (2008). Western Canadian glaciers advance in concert with climate change circa 4.2 ka. Geophysical Research Letters, vol. 35, Issue 7, pp 1-6.

Mitchell, E.A.D., Charman, D.J., Warner, W. (2008). Testate amoebae analysis in ecological and paleoecological studies of wetlands: past, present and future. Biodiversity and Conservation, vol. 17, Issue 9, pp 2115–2137.

Osborn, G., Menounos, B., Koch, J., Clague, J.J., Vallis, V. (2007). Multi-proxy record of Holocene glacial history of the Spearhead and Fitzsimmons ranges, southern Coast Mountains, British Columbia. Quaternary Science Reviews, vol. 26, pp 479–493.

Quickfall, G.S. (1987). Paludification and Climate on the Queen Charlotte Islands during the past 8000 years. MSc thesis. Simon Fraser University.

Weiss, H. (2016). Global megadroughts, societal collapse and resilience at 4.2 – 3.9ka BP across the Mediterranean and west Asia. Past Global Changes, vol. 24, pp 62-63.
Hi Geoff,

Thanks for this! I’m a meteorologist, and find this work quite fascinating and illuminating!

I can’t remember why the methodologies for sampling/analysis are not as useful/intended for use on the most recent several decades of time...why is this the case. When do the paleoclimatogical tools hit their sweet spot and why?

In any case, it’s really the forensic science side of climatology!
Thank you very much, Valentin Albillo and Don Shepherd, for all these founding and very formative articles. This HP12C is truly a fantastic calculator, so full of resources! But I only discovered it recently ...
Which didn't stop me from having had a lot of favorites before !!
(For example, how long did I dream of the HP15C before my father brought me one from Paris - in 1983, back from a providential business trip to Paris because it was cheaper in the major specialist stores - the one that accompanied me during all my high school studies?)
Hi Geoff,

that is sounding very interesting, the topic of your PhD thesis as well as your vita!

(04-19-2020 07:06 PM)Geoff Quickfall Wrote: [ -> ]For an informal taste and some of the HP 41C/CX involvement in the MSc check out my HHC2016 presentation on YouTube.

I'm almost sure I did back then, but I cannot remember. I will check it out again! Thanks for the hint!
My most treasured HP handheld would have to be the HP48GX I purchased in 1995 Smile A little while after I purchased it I bought a 128KiB Cynox memory card for port 1 and a 2MiB Cynox memory card for port 2 . With a merged port 1 I have 256KiB of RAM available Smile

I've taken this particular HP48GX ( I have three in total ) all over the U.S. ( and around the world ) and it's been with me throughout highschool and my university years and through my professional life as well Smile It still works fine, even though it's been dropped dozens of times and almost fried in Indio California Smile It's full of memories and I'll continue to use it until it finally bites the dust, although, I don't think that will be soon Smile


(04-15-2020 05:33 PM)Dave Frederickson Wrote: [ -> ]What is the most treasured HP in your collection?
In this poll "treasured" can mean whatever you like, value, rarity, or favorite.

This is my HP-15C I bought in a computer market near the Technical University of Budapest, where I studied mechanical engineering and I wrote my first RPN program on it: my statics homework solver which solved lots of students' homework just before the deadline.

Why is it very special?

Because this is manufactured badly: the LCD and keyboard on the back, as you can see in the picture and I must to learn how can I use it in the mirror.

(O.o) ...uhh... (>.<)" ...omg... (o.O)


Let's see, the top of my list would be the HP 65 I got from Don Shepherd. I'm a sucker for handheld computers/programmable computers, and having what is essentially the first one ever in fully working condition, along with lots of software and manuals is just exquisite.

Some of my other favorites:

HP 48GX - My first HP, purchased in high school.
HP 42S - Purchased last fall, then upgraded to 32 KB RAM. Goes with me everywhere (partially because I need it to track some fluid intake/output numbers throughout the day, and partially because it's so packed full of other useful programs).
HP 16C - I majored in CS, so it's a given I'd be in love with this one.
HP 41CX + printer - I keep finding all sorts of handy uses for the clock, alarm, and stopwatch functions. It sits proudly in the kitchen, reminding me when the cat needs his medicine, among other things.
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