CAM #4 - Pt 2 What is RPN Reverse Polish Notation / How to use RPN on the HP 12C, HP 15C and HP 50g

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In this video we take a look at RPN (Reverse Polish Notation) and how it is used on the HP 15C (HP12C) and HP 50g.
We look at the concept of memory stacks and the use of RPN vs algebraic notation to solve arithmetic.
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[@bolleke702]

Nice videos! But I have one remark. You pressed ENTER too many times. An experienced RPN user, enters the numbers in a different order, for example: instead of entering '2 ENTER', you start with entering PI, then "Square", then "2 *". Same with the denominator. You should start with 11, then SQRT, then 5 +. The way you do it here, you first of all uses a bit too many keystrokes and secondly, you have the risk that your stack level of 4 is not sufficient anymore with more complex exercises. Cheers

[@77bronc14]

Great video, I like to watch these to keep me sharp. I am a retired engineer and started college in late 1970's and was using a TI SR51 II. Then a friend showed me his HP 25 and I was sold. I switched to a HP21 and that was it. Then from there went down the road, 41's, 31, 32, 33, 34C, 48 and now I am back to the 21. I found a like new used 21 on eBay. Also have three 35s, a 20 and a 32 around here My fear is I won't be able to get any HP RPN's down the road so I collect them.

[@David-ln6im]

Please do a 12C tutorial. Your tutorials are one of the best i've come across. Thank you for providing your knowledge for all of us.

[@geoptus]

As ever, another brilliant and clear explanatory video! Many thanks Martin. Have just discovered RPN (three RPN modes on an Android App calculator I'm using) and I'm totally sold on it - very efficient and clear input method. And I agree, this mode of input does impel the user to think about the calculation at hand...always a good thing.

[@TheMangeGrain]

Thanks again ! Using to your explanations in part 1 I was able to key the example on my 12c (no pi or square key) : I stored a 7 decimals pi approximation in m0 and I used the automatic stack to get pi squared ; RCL 0 ENTER x. "RCL 0" copies pi value in register x. "ENTER" shifts the stack x->y->z->t, "x" key multiplies x*y both containing pi => pi squared.

[@chef1arjunaidi]

Great video! Thanks for pointing out the difference in the stack operations in the 50G and the 15C calculators

[@knudplesner]

note: on hp 50g: 5 enter 7 enter + is 12 but like the 12c and 50g you will get the same on hp 50g: 5 enter 7 + is 12

[@andreduartebueno]

Your videos are very well done; Congratulations! I have a collection of HP calculators. My first RPN calculator was an HP-11C (college), then a HP-41CV (engineering), HP-48SX (master). Recently bought HP-15C-EE, HP-35S, HP-50G, and I will buy HP-Prime. The HP-15C-EE is over, an alternative available is the HP-35S. In this sense I suggest a video on the HP-35S. Again Congratulations!

[@AI-PhotographyGeek]

Really, very good efforts to explaining RPN! Kudos

[@alerey4363]

having to calculate in RPN chunks is a good exercise for kids nowadays, great and clear video, specially showing that the little brother 15c still can do the math besides the limitation in 1 line display

[@RobFisherUK]

One way around the problem with RPN of re-entering everything to just change one value is to enter your RPN calculation as a program, which you can then edit. The 15C allows this, though it's probably easier with the bigger display of the 50g or even the 42S. (I confess I mainly like RPN because it is fun.)

[@pev_]

Sure, BUT entering a program is another level, and has kind of been done also in algebraic calculators with "formula" capabilities. That is, RPN is only the input method and way of thinking about doing calculations, and any programmability is another layer on top that can be done with both input methods. That said, I love RPN, and also the RPL language of later HP RPN calculators (28S and after). :)

[@pablogtz5691]

Amazing tutorial! Thank you very much!

[@ckbaeza]

Clear explanation!

[@danielgustavo10]

Muchas gracias por el tutorial¡¡¡¡¡ quiero ver muchos más¡¡

[@tsm9259]

Thanks for making this video

[@snowpuppy77]

Excellent teaching on RPN. I have thought about getting a 15c to use as a compact RPN calculator. I use the 50g for work. I would have thought I would have known how to use the 15c RPN without reading the manual. Certainly would have been getting unexpected results. Not now thanks to this tutorial. So thank you. By the way when I was in engineering college my first RPN calculator was the HP 28S. Loved it and it became RPN or bust. Then I got a 48SX which still works. I then got a 48G mainly due to its clearer screen, more memory, and built in equation library. My 48G now will not work due to a faulty on key. Disappointing as it is my all time favorite. 50g is growing on me though now that I am adapting to the unwelcome change to the location and size of its Enter key.

[@RedRider2001]

I also had the 28S and then the 48SX. My 48SX worked right up until a couple months ago. :-( Look for a video describing your problem on youtube. You can probably fix it.

[@wisteela]

Very informative

[@robhemsley9181]

excellent thanks

[@armandoandresmeabe8571]

I strongly consider that it is not fair to say that you cannot go back and edit the expression in the 50G. Actually you can do it and quite easy, but you were working in numeric mode wich is not fair. Try again without the exact numeric mode on, so you can leave the expression just as is, then you can press 'enter' to create a copy and evaluate that copy to see the actual numeric result. If you need to modify, just go up in the stack and create another copy to edit it.

[@johnsmith-gd6jl]

how is this 15c compare with 42s ? does 15c handles complex calculations too ? thank you

[@stevecoatesdotnet]

So, which do you prefer? RPN or Algebraic? Since I learnt RPN, I have been using it almost exclusively. I don't think I could get on with having only a single line display though. My HP 35s' two line display is good, and more lines, like on the graphing calculators could be even better.

[@JoeLinux2000]

Thanks, on my CASIO CG50, I don't need to add any parenthesis to the first part. I'm set "Fixed" for 2 decimal places on both calculators (Casio and Android RPG+) and both came out 36.73. It actually took several tries on both. The problem on the CG50 is that I was putting an "=" at the end which caused a syntax error. As for the RPN, I just kept making mistakes and having to start over. I'm not exactly clear when you have to push and when you don't. I will say this: At the moment I prefer the CG50 because if you make a mistake, you can edit what you have entered, but on the RPG calculator a mistake can force you to do a complete restart. I have ordered an HP-G50 like the one you have. From what I can tell, the Android RPG+ app. should be good enough to replicate the "12" or "35" as it's quite close and maybe a bit better than the original HP 12 or 35.

[@JoeLinux2000]

I'm giving up. I find my Casio CG50 much easier to use. You can step through the problem on it, the same way as with the RPN+ App, but of course it's not RPN but simplified Algebraic entry. I like the larger screen, and the fact that problem solutions are held in memory. I've tried entering your practice problem over and over again in the RPN+ but my mind doesn't think that way, and I end up loosing the entire problem when I have to start over again. That is combined with getting the wrong answer about 50% of the time when I am able to complete the sequence. On the Casio you can make a mistake somewhere up in the stack and correct it, and the entire sequence seems to recalculate. It's more like a spread sheet in this respect. Additionally you can enter the entire problem completely or in segments like you did with the RPN devices. RPN is interesting, but it's certainly not the greatest system of all time. It's more like an improved slide rule, but equally outdated by improved microprocessor technology.

[@bolleke702]

@@JoeLinux2000 RPN is certainly more advanced than the old school algebraic calculators from the 70s, 80s. And modern algebraic calcs (textbook) are arguably more advanced than old school RPN calcs. (they both have pros and cons) But today modern textbook calcs are certainly not as elegant as a "modern" RPL machine where you can have everything on the stack and the stack works as I/O for programs, and other functions. You are aware that all computers work internally the RPN way, right? (or postfix) So I wouldn't say it's outdated. ;-) Cheers

[@jimmysyar889]

at 14:13 if you understand algebra you know you didn't have to type a single parenthesis

[@Feierabend666]

Good video and nice introduction to RPN. In my opinion, while historically important, it is not the best mode of input any more. Textbook entry is available in cheap calculators (TI Multiview and Casio VPAM) and it is much superior - with even less less risk of error and, as you have shown, the potential for expression re-use. I would advise against learning RPN entry, I think it is a useless skill. This comes forme someone who has gone through engineering master studies on an HP 28s, which I still like much.

[@Falcrist]

I took some time to do this calculation on the HP Prime, the TI-36X Pro, and the TI-30XIIS. Algebraic input requires at least 28 keystrokes to evaluate this expression. The textbook-style input requires 26 keystrokes. The RPN input requires 25 keystrokes. Algebraic input just sucks. It requires more thought ahead of time AND you're not going to be able to see the entire expression. Terrible! The textbook style input has three advantages: 1) It allows you to see the entire expression at once, which is handy for proofreading 2) You can scroll up and see expressions you've already used, allowing you to copy and modify it if needed. 3) It requires very little thought, since you don't have to translate the original expression... you just copy it into your calculator. RPN has two advantages: 1) It allows you to see intermediate results, though this is somewhat less helpful. 2) It's extremely natural once you get used to it. At this point I have to give the advantage to the textbook style input. It's very good and very fast once you get used to it. However, I'm going to spend a couple months using the HP prime in RPN as my main calculator.

[@Falcrist]

*Update!* I've been using RPN exclusively for several months now (in the middle of an electrical engineering degree), and I can confirm that what I said above is true. Textbook-style input has the advantage IMO. However, I managed to get my hands on an HP 42s, and that is now my main calculator. Why? Because *almost all of it's functionality works in the complex domain.* That is pretty much unprecedented among scientific calculators. Even modern scientific models like the TI 36X Pro, Casio fx-115ES Plus, and even the HP 35s just don't have good native support for complex numbers. The ability to compute with complex matrices and exponentials along with the simple programming mechanism has made me an HP fanboy. My backpack now generally contains an HP 35s, an HP Prime, and an HP 42s. The 42s is the one that gets the most use at this point.

[@JoeLinux2000]

@@Falcrist, interesting observations. I'm just an "old guy" hobbyist trying to learn the math. Of the ones I have, I think the Casio 115 ES Plus is the handiest because of its size and key layout. The HP RPN+ app has a lot of neat features like being able to convert decimal time into Hours, Minutes, and Seconds. Maybe the others can do it, but it's not as obvious. I end up using the Casio CG50 the most, but that's because it holds the problems in memory and and backlit screen is nice. What's against it in my opinion is that there are too many menus and you have to search for what you want to do. I can really see where these pocket RPN's are really nice.

[@Falcrist]

@@JoeLinux2000 4 years later, and I still actively switch between RPN and "textbook-style". My recommendation for textbook-style is still the TI 36X Pro. It has the fantastic ability to scroll up and see previous computations. Also check out the DM42, which is a modernized version of the HP42. It's fantastic! :)

[@GRBtutorials]

You use too many parentheses. For the first fraction, you can push the fraction button, add the numerator, press down, and then the denominator. For the second one, just add the numerator, fraction button and add the denominator.

[@B.A.Gondal]

Great tutorial....however I would say that RPN would be totally useless in my calculus and linear algebra classes....u make mistakes all the time and RPN just takes hell a lot more time than algebraic format....I wud say it only works better with simple arithematic....not wen u r dealing with long complicated equations....

[@RedRider2001]

Incorrect. The Stack plus RPN makes solving complicated equations far easier than compared to traditional calculators. The newer algebraic calculators may be more intuitive to someone not familiar with RPN but then you're just typing in symbols and numbers and you don't do any evaluation of it yourself at all - the calculator does all that for you. So if that's better from your perspective then so be it. Source: Me, I used HP RPN calculators throughout engineering school.

[@JoeLinux2000]

I'm inclined to agree with Asympote, but at the same time, I see RedRider's point too, I would like to become skilled at both. How can you delete just your most recent "X" (stack) so that you don't have to start the entire problem over again?

[@etch4]

Horrible as always. TI-36 ( . . ) wtf ? 15:14 RPN efficiency 2 pi NOT 2 pi . Automatic stack lift ? 18:14 again, he is not learning.

[@fernandoj.sulsonaanziani6195]

RPN is too fast for modern people. Modern people can't handle this.