Calculator blog

Musings and comments about our common interest


Published on by

HP 15c LE last production run.

It was beautiful while it lasted…



Several distributors have confirmed us that the last run of HP 15c has already been distributed, and that HP does not plan to produce more.


While it has been a fantastic premium product, we have to realize that this is a niche product, and, in the grand scheme of things, completely irrelevant for HP. Any of the other products made by HP is produced in quantities 1 or 2 orders of magnitude greater than our beloved HP 15c; some of them, even three orders of magnitude!


I know that some of you saw this coming, and ordered more than one unit. There were some that ordered as many as 10 (I guess that there was some ebay reselling involved) but several ordered 5 units.


Now is the time to take a decision that may last for the rest of your life…Seriously now, while if I were HP I would keep the 15c running for as long as it sells, the production logics for this kind of product implies that it may well be the last time that this model is produced.


I guess that we did not behave well, as a community, with respect to the HP development team regarding this product. As this community has been asking repeatedly for this product, the development team set to produce it, based on an already developed body – the one of the HP 12c; but it seemed to me a labour of love, because the potential market did not deserve any development time or effort for such a small niche.


Once this product had been released, as a gift for us all, there was a lot of criticism on the grounds of supposed low quality. I have and use an American unit of the first batch, and another of the European batch, and both worked flawlessly. Of the more than 500 units sold by us, only three units have been defective. There were criticisms as well about the keyboard, but anyone with experience with the current HP line would attest that it is the best keyboard in production with the sole competition coming from the HP35s and HP17bII. And compared with the original…well, in my 1985 unit, the keys are softer and shiny, but not necessarily better.


The presentation of the product was as well ahead of any other product - either HP's or the competition's (the anniversary 12c had a smaller box and no printed full manual. The only missing item in the HP15c for a completist would have been the Advanced Functions handbook, itself a masterwork in itself.)

As for the bugs…well, there really was only a bug, which had never been a problem for me (since I did not use PSE but R/S in general in my programs).


However, I found so much bad karma on the comments that, if I were a member of the development team, I would know where to put our community demands…


Read entire post
Published on by

Why using a handheld calculator nowadays - part I

Many people, when they see me using a calculator in my job, argue about why using now a calculator, when there are so much more powerful alternatives. They always try to convince me about how much better is a spreadsheet, etc.

Let me try to organize my thoughts about what's the point of having a calculator nowadays, when we have computers and, let's not forget, smartphones. If you are reading this, chances are you are as nut about calculators as myself, and you are as well faced with those questions from time to time. I hope then I can give you some elements for discussion. I would like to ask you to post your own reflections, to reinforce my arguments as well.

(Other times I get challenged about collecting calculators, but for that, to be honest, I haven’t found any good argument in our defense!!)


In order to systematize the discussion, let’s see first which are the most likely alternatives to your calculator (the most likely, not all of them. Remember the HP-01? Or more typically, the Casio watch calculators?)

  • PC running spreadsheets
  • PC running specialized mathematical software (Vgr. Mathematica)
  • PC running a calculator program
    • The operating system’s own calculator
    • Emulated “true” calculators
  • Smartphones
    • Own calculator
    • Calculator Apps
    • Ipads and other tablets

In this post I will deal with the first ones, leaving the others for a further post

PC running spreadsheets

On one side, it is true that an spreadsheet carries you further and with less effort - and it leaves a trace of what you are doing. You don’t need to write with your pencil the intermediate results.

Today spreadsheets have very powerful instruction sets. And it is very likely that what I now think that can't be done with spreadsheets, is more due to my lack of knowledge of the tool than actual lack of that feature. I am now thinking of all matrices-related things. 

PC running a mathematical software (like Mathematica)

I have to be honest with you – the last time I used one of these, I was still using MSDOS, when I was studying engineering in the 80’s. For me, this option is limited to Academia – which is the environment that would buy and maintain this kind of software. I have to confess that my opinions on this area are based on very out-dated information, and I cannot add value. (here is where you, reader, can join in!)

Before the IBM PC was born, there was a Personal Computer produced by HP – the HP85. It was a fantastic machine, running a BASIC-oriented operating system, with a big number of mathematical operations for the time, and that could be programmed for any kind of mathematical challenge. In this case, some of you could tell me that it was not an alternative to calculators: it was, in fact, a calculator (its CPU was based on calculator CPUs, at a time where 6502, 8080 and Z80 microprocessors were common on other machines)


There were ROMs that enhanced its capabilities in areas that are the realm of calculators: matrices, etc.

PC running a calculator program

I am running in my Mac a couple of different HP15c, a HP42s, a HP41cx, and under the Windows screen in parallels, a HP50g. Even the most advanced scientific calculator (the wp34s), started its life based on the SDK of the 20b  - if I am not mistaken. I have written a blog article for the humble Mac OSX calculator, that can be configured as RPN as well.

The choice would be even bigger, were I running Windows as main machine. I have not explored the options for Linux. I might be interested if I still was in the Windows camp, but I moved to Mac and I’m not thinking about changing again.

The discussion of the many working alternatives for calculator programs is well beyond the scope of a single post, and deserves an article or a series of articles from somebody much more knowledgeable than yours truly. Let’s focus instead on the advantages and disadvantages:

  • Advantages:
    • Speed: several orders of magnitude running programs, except in case of the latest calcs, like the wp 34s, hp 50g and hp 30b
    • You can have all the options – you are not limited by memory or bays used, like in the HP 41c family, or the HP71b
    • In most of them, the numeric keyboard works as well, as most of the basic operations. The keyboard shift works as F.
    • In some of them, there are side windows that can show the status of the internal registers, from seeing the whole stack and last x registers (good), to seeing all the CPU registers and flags (geeky).
    • You can take all your calculators with you, instead of being limited to 2 or three. (I seldom travel with 2 calculators – most likely I take 3 with me: the hp 15c in my jacket pocket, the HP17bII for calculating at work, and either the hp 50g or wp 34s for fun at the hotel.

  • Disadvantages:
    • You need to switch on your computer, and then you need to look for the application and switch it on as well. This takes 1 minute – unless you’re working with Mac – then you’re going after 16 seconds. Let’s see what Windows 8 brings to the table.
    • In many cases, the calculator does not keep the state you left previously: stack and memories. This is not really a problem of the idea but of the implementation.
    • There is no comparison between keying in in a physical keyboard and doing it with a mouse.
    • It occupies real estate on your screen, the same as a calculator occupies real estate on your desk – however, screen estate feels always smaller and cramped than your own desk. (by the way, this is the reason that my HP19bII never takes a lot of use – same as with the HP71b.
    • If you are using it in conjunction with Excel or other program, the switch from one to the other is never instantaneous – you need to click twice on the window – once to select it, another to start doing what you wanted. This happens between any two windows applications, by the way. 

There are times when you can’t use a computer – meetings!

There are two kind of meetings in my company: with and without computers. When you see a meeting where everyone is using a computer, you can assert than more than 50% of the attendees are not really there, but emailing or finishing their presentations for their turn. Therefore, they are not listening to what whoever is speaking has to say. 

More and more, some managers are insisting that laptops are closed while the meeting takes place – at least, while they are speaking! Therefore, the calculator is your only alternative to number crunching during a meeting. 

As well, in a meeting you need to give a fast answer, and this would be difficult with a computer. With a calculator you can do fast and dirty calculations; with a computer, you lose and inordinate amount of time formatting even the most minute calculation. There is a brain switch that allows you to take approximations and shortcuts with a calculator, but impedes all but a perfect mathematical model when you try to do the same thing with Excel!

As conclusion of part one: it is not clear at all that a computer can take all the work a calculator does. Let’s see in part two what happens with the other devices mentioned at the beginning of the article.

Read entire post
Published on by

At long, long last...The HP15c Limited Edition Arrives !!

We have been informed that finally the HP15c will be arriving to Europe on the 2nd half of January 2012. Shipment to final customers on week 4 2012.

The sales price has been set at 109,99 €.  You can find it here:

HP 15c Limited Edition

The buyer will receive a substantial box, ideal for a gift to an engineer friend (my best engineer friend is myself, by the way), or as an exhibition box in your collection. Here you see it as you will receive it, with the plastic cover:


And here without it:


Once opened, this is what you see:


And here you have the calculator, together with an original unit:


The pouch is substantially better than the one in the 12c. I prefer it to the original as well - YMMV

There is a difference with the back: is black lettering on silver metal finish. It seems to have a vernis on top - after 3 months using it, it has not lost any part of the labeling.


It can be "repurposed", as any new 12c can. Please see the connector between the 2 batteries.

Please see here a close look:


Read entire post
Published on by

HP15c clone coming back - but now with a competitive advantage!

If you remember, some time ago we reviewed a project for a clone HP15c calculator made in Switzerland. While the project was extremely interesting, it had the worst possible timing: it coincided with the reissue of the HP15c by Hewlett Packard. With good sense, the creators backed off and re-thought the project, in order to give the user something more than the original did.

I am carrying the HP15c Limited Edition every day with me, and while its size is smaller than most calculators, it is a tight fit in my shirt's pocket, and it fits well in my jacket's; but sometimes I would like it to be smaller.

Enter the HP15cc:

First a pre-production sample



Then a more developed sample:



I look forward to get one. and you?

Read entire post
Published on by

Tutorials for HP15c

It is amazing the vitality in our admittedly small and "vintage" hobby. As soon as a new edition of a vintage calculator appeared, there have been people working on it.


I plan to give some of these HP15c calculators to my children (I will buy a decent stock of them for myslelf), but it is good that there is already a programming tutorial for it. I have included links to it in my Manuals and Support page. Thanks, Eddie for it!


HP15c Programming Tutorials from Eddie´s Math and Calculator Blog

Chapter 1: The Stack

Chapter 2: Basic Programming

Chapter 3: Registers

Chapter 4: Tests

Chapter 5: Subroutines

Chapter 6: Loops

Chapter 7: Solve and Integrate

Chapter 8: The summation program

Chapter 9: Derivatives

Chapter 10: Statistics

Chapter 11: Flags

Chapter 12: Memory and indirect registers

Chapter 13: Indirect Addressing and subroutines

Chapter 14: Complex numbers

Read entire post
Published on by

No HP15c for Christmas

We have received confirmation from HP that there will not be that "early" shipment of HP15c for Europe, and that the only HP15c will arrive by the second half of January.


As I have been using a sample for the last 2 months, I can tell you it is a pity.

The other day I opened my pristine, original, 1985 hp15c and surprised myself preferring the key feel of the new one. Maybe due to ageing, the keys in the old one are "mushier", although still very precise and comfortable.

For those customers that ordered an hp12c anniversary and told me to wait until the hp15c arrives to ship them together, we offer to send to the 12c Anniversary and we will deliver the HP15c with free shipment when it arrives. Please contact us by email to

Read entire post
Published on by

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!

Read entire post