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Calculator blog

Musings and comments about our common interest


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HP35s Appreciation

You know my fondness of the HP17bII in all its different models. The last one, while not purely an HP, has the best HP keyboard around, a much better screen than the original HP17BII and a nice aspect that can be presented in any business meeting.


With the same body, and nice, professional colour scheme, you can find as well the HP35s, a successor of the ugly HP33s, that sports the same very nice keyboard and a 2-line alphanumeric screen. Here you have a picture of it:

The HP35s shows the first wide ENTER key in several years, and we can only hope it returns back to the graphical calculators again.

I entered the HP35 with some aprehension, after reading some negative reviews. I have to say that it appears to be an excellent calculator. Despite my limited time with it, it is clearly better than the 33s (not too difficult), and much better than the lower current offerings. Still, it does not hold a candle to the HP42s in sheer power, or to the 15c (my current favourite in its latest LE version) in ease of use and elegance of design.

Let's focus instead in what it does have that the 42s hasn't:

  • constant library - useful in physics
  • Algebraic mode: cleverly designed, a truly "equation operating system", as Gene Wright named it.
  • Three modes of complex number notation
  • fraction mode(s)
  • unit conversions on keyboard (not submenus)
  • the ENG-> and <-ENG keys, useful when choosing electronic components like capacitors and resistors (it's oh soo easy to drop a zero when specifying a capacitor...), but is really just a convenience, not something you need if you really put attention to what the result should be.

I need to delve deeper in this calculator: the programming paradigm, the use of variables and memory, the huge number of possible registers, etc. At first sight, it seems intenresting for a student, but does not have the same professional appeal of an HP42s or the newer HP15c LE. As it is now 1h22 i9n the morning, let's leave this for another day.

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The HP12c Anniversary is now in stock !!

We have finally received this afternoon the shipment of HP12c Anniversary in the warehouse. We will begin shipping on Monday the pending orders to our customers. All of them should have received it by the end of the week. We hope you enjoy them!



If you remember the discussion about different keyboards of ARM HP12c, the Anniversary belongs to the "good" ones.

Now we're just waiting for the HP15c Limited Edition!

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HP Operating Environment limits - HP15c Limited Edition

Do you remember when old HP product manuals came with "operational limits" notices? I have seen several that stated operating maximum and minimum temperatures, as well as storage temperatures; I seem to recall that there were operating maximum altitude on some of the products as well.

These notices were inherited from the time where HP was the world's best measuring instrument producer - and you needed to know if the measure had been taken within the right operating bracket - but that's not the case anymore.

At least you can make tests for yourself. The HP15c LE works well at -5ºC (23 ºF), at 3.571 m (11.716 ft) of altitude, on Jungfraujoch Sphinx observatory:


The view from Jungfraujoch, in mid-Switzerland, is amazing - you see miles and miles of glaziers, and several 4k+ peaks. You can see as well possible falls of more than 2000 m when you stop with the train in the north face of the Eiger peak - since 1935, at least 64 climbers have died trying to climb it. No wonder I took the picture firmly grabbing the calculator!

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16 € reduction in the HP50g Blue

We have finally found a good, reliable source for the HP50g Blue. We have been able to lower the price to the level of the HP50g black - 119,99 €, VAT included (without VAT for overseas shipments)

Apparently, this model is good as well for some view diseases - see Deuteranopia and HP50g


It can be shipped to the US as well, of course!

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The WP 34s is back!

The wp34s is back!

Finally we received the overlays of the current approved design and we are ready to update the firmware of brand new HP30b s into the most powerful RPN calculator ever - with permision from the mighty HP42s

Eric's newer overlays are better than the previous, initial batch. You can choose between coloured shift keys or white; and you can choose as well between both division signs: / and the two dots with a dash in the middle. All are in the overlay for you, the user to choose.


There has been significant evolution since we updated the first calculators - now you can do matrix operations with them as well. 


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More comments on the HP12c keyboards

If you remember our previous post, we were talking about the different keyboards in HP12c's of late. Seems that it is due to products from different factories - the big % sign coming from the Invertec factory and the small % coming from Kinpo.


Here you see the codes on the back of the unit: IN04 and KN05.


Now, all the new 12cs I am receiving belong to the "big %" type...except the new HP12c Anniversary (due in Europe from next week on!)


(By the way, the HP15c Limited Edition comes as well from the same factory, and you should expect the same quality - I can attest it!)

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Different keyboards in new HP12c

I was surprised when one of my customers told me that I had sent a calculator with a sub-par keyboard. He sent pictures to me showing very different % keys, and others as well. Here are pictures of the "expected" keyboard and the "received" one:

Expected (and this is the one I am accustomed to see)


Received. Main differences: the % keys; the printing seems sharper; the numbers are clearly bigger in size but seem thinner:


My customer told me that he has heard that this keyboard is clearly worse in key feel than the other.

Here are both side by side:


Once received the sample, the keys were found to be equal to the "desired" keyboard, but it surely looks different!

In contact with my sources, it seems that most recent samples are of the "left" design, as opposed to "right", older one.

Of course, both of them are of the ARM variety.

Surprisingly, the anniversary version comes with the "old" keyboard.

No difference as well from the back:


(Same order)

Any knowledge to share on this?

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Más sobre: HP12+, HP12c
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HP15c Limited Edition manual

Nowadays most of the calculator line comes with a starting guide and a CD with the manuals. If you want to read the manual "the old way", you had two practical options - print it or download it in your Ebook of choice as pdf document. I have tried the second - it is a pain. The best way is the computer, of course (some manuals can be ordered from HP itself).

Even the HP12c Anniversary comes with a starting guide. But not the new HP15c Limited Edition. It is clear to me that HP has gone out of their way to create the HP15c, including things that they are not including in other models (and that no other producer does in my experience):


As you can see, the manual is slightly bigger - but you need to remember that the original manuals were very small (same for all Voyager line). I have not an HP41c calculator at hand, but it seems to be roughly the same size.

There were three possibilities when HP set to do the manual: start anew, try the best photocopying device available or try to imitate the original in every possible way with current means. This was the alternative chosen.

All pages have the same content, including the numbering, but written in different (but similar) fonts. Some graphs have been scanned instead of re-done. They were grey-blue in the original, different shades of grey in the new one. Let's see some examples.

Pages 158-159 in the new manual:


Same pages in the old manual:

 (although it cannot be aprreciated, even the footnotes are the same!)

Pages 174 - 175


And, in the old manual:


It seems that the same process was not possible to do in time with the advanced functions manual. This is an excellent book, and should be read from cover to cover by anyone interested in mathematics and computing - regardless of the calculator you have!


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Some speed tests comparing old and new HP 15 LE

Lets now do some speed calculations between the 2 models - old and new:


Let`s try to calculate a 10-year IRR with the following program, which uses the solve function on the following Net Present Value program:



2 - from % to decimal




1/x - calculate 1/(1+i)



ENTER - to load the stack with 1/(1+i)

RCL .1 - number of periods (so that is is kept for further trials with other interest rates)



LBL .2 - loop for periods

RCL + (I)

X - calculates f(n) = (f(n-1)+ I(n))/(1+i)


GTO .2 - Return if not 0

RCL + 0 - Add start cashflow


Let`s now try with the following cash flow

Initial -126.000

year 1 3.750

year 2 2.750

year 3 4.000

year 4 5.000

year 5 4.000

year 6 5.000

year 7 4.000

year 8 5.000

year 9 4.000

year 10 250.000

We put a starting value of 5%, to get it started.

With the old one: we launch, and wait, and wait, ..., and wait,...3' 34 secs. This program is a nice help for my financial job, and useful for short examples of up to 4 years - but completely impractical for business. Imagine a meeting room waiting for your results, if the cashflow to analyze is 10 years.

With the new one, around 1,5 seconds. We're in business !!!

By the way, both gave the same result, up to ten digits accuracy: 9,389956649%. This is yet another proof that both calculators share firmware.(let's be accurate - it is not a proof, but a hint)

Let's try now with the standard Time Value of Money program that appears in the advanced functions manual. And let's try with the longest function - the calculation of i for a formula

New model: around 1 sec.

Old model: 53 seconds.

A banker could not wait that long for an answer! However, the new one is acceptable for business.

I have tried to put a couple of comparisons of programs and situations that may happen in reality - not just a closed loop that no one will ever use. In this view, the new calculator allows for a number of applications that the former one could not do in a practical way.

Other example: inversion of a simple 4x4 matrix

Old 15c: 10 seconds

new 15c: clearly less than 1 second

(in this case both units were practical for use in an examination - more so because no modern teacher would suspect that a so humble calculator could do matrix inversion!!)

Next day we will talk about the look and feel.

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HP15c Limited Edition arrived

We received the first samples on Friday afternoon, just before leaving for the mountain cabin. I opened it and played with it, but took it with the box and my trusty HP15c from Oct. 1985, made in USA, for meaningful comparisons.

So fast I was that I took the camera but not a proper flash. Hence I took pictures leaving the cameras on the balcony floor. The strong sun washes out the colours in most pictures, so all differences get exacerbated.

First of all, let's see the box. It is substantially bigger than the HP12c anniversary. Let's see both:


And the anniversary one:


The reason being the inclusion of a "real" manual instead of a starting guide as in the rest of calculators.

The manual is equivalent to the original manual, set with modern letter types and current HP design, but for the rest is equivalent to the old one - errors included! It is as well bigger than the original.

Here it is without the protective plastic:


Please note that the strong sun makes the little dust specs appear more clear. I had already opened the box and played with it - hence the dust.


And now for a comparison between the new and the old. Be aware that my old one is nearly pristine, and I separately bought a true leather cover in dark brown colour:


While both calculators are black, the newer is blacker than the original, but the strong sun enhances the differences.

The pouch is slightly thinner than the original, but clearly thicker than current HP12c versions - included the Anniversary. Look for a comparison (the one in front is the HP15c's):


 Now, a look at the back. The new calculator needs more room for the batteries and therefore less is left for the "instructions" in the back. Let's see how it was in the original:


...and the new one, in plain metal. I have removed the battery cover so that you can see the nice Lemo connector that will allow us to update the firmware and eventually change it for a new one. (can perfection be improved upon?)  Let's see how it ages!


By the way, do I feel proud of the low serial number!

And now the naked frontal view:


Sorry for the dust! It was not that much in reality.

Now, for a comparison, the old one:


As it is too late in Europe, I will continue tomorrow with a proper review on other aspects. Before entering in detail, let me say that I am very happy with it, and that it surpasses the original on several counts - including key feel. 

More tomorrow.

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