Calculator blog

Musings and comments about our common interest


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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:


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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

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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

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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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