RPN: Just for Engineers?


In his article "The Demise of the Slide Rule (and the Advent of Its Successors)" in the Fall 2003 issue of The Journal of the Oughtred Society Otto van Poelje of the Netherlands wrote in part:

"...The HP 35 gave the engineers, just like the good old slide rule, a special status, not only
because of its high price and flashy design, but especially because ordinary people could
not work straightaway with RPN: in RPN notation the calculation 5*(3+2) had to be entered
as 5 ENTER 3 ENTER 2 + * . ..."


.....or 3 enter 2 + 5 X. I don't buy the part of Mr.. van Poelje's theory about "ordinary people could not work straightaway with RPN". I'm so ordinary and average i ought to be grey and i use nothing else. Besides; there were lots of RPN calcs around before the 35. I admit that the five i can think of offhand were pretty exclusive too, but the thing about the 35 was that it was the first pocket calc to do transendental functions. Techies who did not work at desks no longer needed to carry around phone book sized trig tables just to get half the accuracy. The only reason that 99.9% of all surveyors stopped salivating at the 35 was that the 45 came along: "WOW! It can't get any better than polar-rectangular!

Still; the 48 series, the 41 series, the enduring 12C and the popularity of the 17b puts the lie to his "engineers only" idea. Yes, hindsight is 20:20. I see his point but imho the only reason rpn is not THE notation is that, statistically speaking, half the people in the world are even dumber than me and a lot of the rest are too lazy to learn the mathematical order of precedence.


Right on db! I could not agree nore. If only I could get my engineering/science students interested in rpn today. These kids mostly look at rpn as some strange way of doing business-TI did a good job in hooking them on algebraic notation. I can't seem to interest them in the 49G+--TI 89's seem to be the "standard" now and this prof just has to reluctantly go along with it, at least for now.


Hi, all;

cannot agree with the focussed affirmative: "ordinary people could not work straightaway with RPN". Instead, I support d.b.'s always clever analysis (Hi, D.B.).

I'd add that almost 22 years later, the HP12C still keeps its place at financial markets, and there are not so many engineers there, instead many mathematicians and lots of businessmen, MBA's, market analysts... They are far from being "ordinary people", of course, but their main concerns are far from being the operation of a particular calculator and its operating system. And I'd guess their HP12C's do not have wearied out [n], [i], [PV], [PMT] and [FV] plus digit-input keys only, instead [ENTER] is included. And HP12C users know it well: there's no need to understand RPN to use its financial resources. But I'd never seen any HP12C owner that cannot help proudly explaining how to use it to anyone that asks for. [ENTER] key included!

About RPN mechanics: if you know how to use pencil and paper to perform computations, than you already know RPN well. Simply use [ENTER] when you finish writing one number and are ready to begin writing the other. In fact, I add an equals sign when writing an algebraic expression, but I cannot remember any moment I needed to write an "equals" sign when actually performing addition, subtraction, multiplication ort any other math operation. And that was the basic line I took when trying to understand RPN: if I know how to solve an expression, I'll be able to find its numerical result by using RPN-style keystrokes.

I think I have already written something like this sometime ago... a year or more, perhaps.

My thoughts. And my 2¢, too.


Luiz (Brazil)


I am obviously with the majority. Mt wife is pretty smart but she hates maths. It took her a little time getting used to RPN but she hates using anything else now.


I have to disagree with Poelje. I am an accountant and I use RPN based calculators all the time. It just takes practice.


I'm a metrology technician, not an engineer. I was very happy when I discovered the 28S; for me, it works just the way that a calculator should work. It's much more "natural" than the "algebraic input" user interface calculators I'd tried before.

I've also noticed that children who aren't already indoctrinated into the arcane methods needed for other calculators seem to have no problem learning to use RPN/RPL calculators for basic arithmetic.

To be sure, a good many "ordinary people" do have a problem when they first try an RPN/RPL calculator, but I expect that that's because they have to "unlearn" what they've learned about other calculators. Too bad that so few are willing to make the effort.




d.b got it correctly when he notes that it was the availability of the transcendental functions which was the big attraction of the HP-35. Where I worked we didn't find the availability of polar-rectangular conversions to be a big plus for the HP-45. Rather, we liked the built in statistics capability which was only a small taste of what was to come.

On the HP-12C: I was with the customer representative in a bank back in the early 1990's. She had a 12C on her desk but was using another desktop calculator for routine calculations. It was one of those business-oriented devices which mimic the workings of mechanical adding machines, the system that I call AML (adding machine logic) to differentiate it from RPN and AOS. At the time I didn't have a 12C in my collection and asked whether she would sell it since she wasn't using it. She would not and explained that it was invaluable for compound interest and amortization calculations of all kinds which couldn't be done on her four function desktop machine.. When I later found a 12C at a garage sale I was not so much impressed with the machine as with the documentation.

On languages: back in the days when HP and TI were competing fiercely with the likes of the HP-67, SR-52, TI-59 and HP-41 there was a lot of irrational flak going around about the merits of RPN and AOS. The van Poelje paper reports that HP folks talked about the TI folks as being from "the dark side". The TI folks came up with an alternate meaning for RPN, namely, "Really Pathetic Notation". In those days I eventually learned to rely on the opinions of what were called bi-linguals; i.e., individuals who were truly capable with either system and who typically would say that either system works well.

When Casio came out with the first graphing calculator they used a system that was different from both RPN or AOS and looked like a cross between AOS and a higher order language such as BASIC. TI used a similar language that they called EOS for Expression Operating System when they came out with the TI-81.

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