Calculator blog

Musings and comments about our common interest


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RPN or not?

DSC_7337_001There is yet another discussion in about the future (if any) of the RPN/RPL entry method (henceforth called RP*, as it is cleverly done in that discussion)

There are a lot of sound opinions there. It is clear that no one of the posters is in denial about the real situation. RPN is the most effective entry method when speed is a fundamental factor (in chained calculations, for example), and when the user knows what he’s doing.

However, this doesn’t apply in an educational setting. There, it is much more important that the boy learns from what he’s doing - and RPN lacks the clarity and readability of algebraic/textbook data entry. Moreover, RPN is not compatible with most current CAS systems, which compounds the problem further. I wander how HP was able to squeeze RPN entry method in the HP Prime spec definition. Probably is the only thing that keeps the Prime a HP - both hardware and CAS have been developed elsewhere (although mainly by HP-related people: guys that have been working for (or with) HP for an extended period of time)

So what is the future for a RPN-enabled calculator? Will it live only as long as people as you and I live? My 12-year old son prefers RPN - but he has not huge experience in calculators. At least there is hope!

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More about: RPN
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RPN and the HP19bII

There was an interesting discussion lately in forums. Has RPN crippled you for other calculator methods? Are you able to reasoning calculations in another way? Can you use comfortably another calculator for any extended period?

I, for one, started off with RPN calculators when I was 12 years old. My first calculator was an HP33c - the second simplest model in the Spice lineup. Before that, my dad had taught me to use his HP37E financial calculator. I am pretty sure that he didn’t go much farther than using proficiently all % functions. I don’t think he ever mastered the TVM functions. At least I never saw him using them, or explaining them to me. In retrospect, it was a huge pain to have a calculator without permanent memory (all E version lost their memory contents when switched off)

At that time, calculators were not too popular at any student level. Most of my classmates didn’t have a calculator at all, and any who did, had the lower level Casios. I learned the calculator with the excellent user manual provided. The examples and the logic behind was unrivaled at the time; only with the hp85 personal computer I have seen a better package.

In class, the RPN calculator alienated most of my classmates. They would ask me for it in the middle of a test, only to come back to me in anger asking “where’s the equal sign!”. I learned to tell them in advance that they would not be able to use it. (While RPN is extremely easy to learn - you can get the beauty of it in just 15 minutes - a test situation is not the best environment to learn it!) On the other hand, I soon became completely unable to perform chained calculations with a “normal” calculator. And at that time no one had a programmable calculator: none of my teachers would know what that meant, or were able to identify one. So I had an undue advantage in the first courses, since I was able to program small little programs for the tests (with its very limited 50 steps; but I have been able to program a Net Present Value program in just 24 steps of the hp15c)

Later, when I started engineering, 5 years after, the calculator still was working - a testimony to hP’s engineering and quality of yore. But then the battery bay broke, and I needed to get another calculator. At that time, the one to get would have been the hp41c - but it was very far from my reach. So I ended up having a Casio 790p - a Basic-programmable machine, which had a couple of weak points but mostly got me through engineering. I was able to program in it all that was required in engineering - in particular equation system solving through matrix inversion. Now it seems all so easy, with most graphical calculators proposing it as a basic feature; but at that time, you had to program it for yourself! Be aware that, at that time, all numerical methods were taught in FORTRAN, to be run in a VAC computer. So I still was at the programming forefront. And, amazingly, the 2kb memory limit never was a problem. Later I have been using the hp71b, which is a better machine - but surely not ten times better, as the price would suggest.

With the Casio, I never managed to chain calculations the way you easily do with a RPN machine. Fortunately, I just needed to write the whole expression and evaluate -the same way it is now done in the Prime or HP50g textbook mode. But my mind was still wired for RPN.

Later, when I started my MBA in Barcelona, the Casio started to fail by its hinges, and I had to get another calculator. At that time, the right choice for business was the HP19bII. You could use it both ways: algebraic or RPN, but I always set it for RPN. (The fantastic solver was - and still is for its sibling hp17bii+ - a textbook entry concoction). I am still fascinated about this calculator. It was the first financial calculator that included trigonometric function, and even hyperbolics! Not only that - perusing the manual, I even saw measure conversions. It was the universal calculator of that time for anyone in business - provided he was not a pure technical person.

We will elaborate more on the HP19bII tomorrow.

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More about: HP19bII, RPN