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  • #16
    I still have a Sharp EL-515. solar powered scientifiv calculator, which I bought around 1980 IIRC. It still works, but I had to repair it some time ago, and the solar cells seem a bit wonky and the display goes on and off depending on incident light from an LED flashlight or warm white CFL.



    Mine is a little different - not the "S" version:


    Last edited by PStechPaul; 07-19-2020, 01:46 AM.
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

    Comment


    • #17
      Originally posted by elf View Post
      What's RPN?
      RPN = "reverse polish notation"
      hardcore number geeks, engineers and physicists tend to use that style.
      In which you enter all your numbers followed by whatever you are doing to them
      For example, you would think 3x5=15
      but in RPN you would enter 3 5 x

      FWIW my "EDC" calculator is a TI 35-plus, but I'd like to learn the slide rule someday simply to honor my Dad and my uncles.

      Comment


      • #18
        When my HP 41CV quit after 35 years, I was really ticked. The bad part was total unobtanium, and the calculator had been NLA for decades.

        So I got a "herd" of TI scientific calculators, all the same model, solar type. Sure missed the RPN, the mixed mode* of the TI units bugged me for years. Finally found a used 41CV, and now I am no longer used to the RPN, and I do not make full use of the "stack".


        RPN.... Stands for "reverse polish notation". I no longer recall just where that name came from, you can look it up, or someone here will remember and explain.

        In standard arithmetic calculators, you would put in "2" then the multiplication symbol (x) and then "4", then hit the "=" button, at which time the answer appears.

        With an RPN calculator, you put in "2", the "4", then the multiplication symbol (X) and the answer appears. The "operator" (in this case the multiplication symbol) always is entered AFTER the numbers it operates on.

        The HP calculators also had a 4 place "stack", so that you could handle something like " (1+1) x (2+2)" without fiddling with parentheses. You could enter "1", "1" "+", then "2", "2" "+", then "x" and get the answer.

        The lowest of the 4 locations was displayed.

        The first number entered would go in the bottom register of the stack, the second would push it up and replace it, and the operator (+) would add the two, with the answer appearing in the lowest stack entry.
        First you would have

        0
        0
        0
        1

        then

        0
        0
        1
        1

        Then

        0
        0
        0
        2

        Then entering "2" would push that result to the second stack location, and entering the second "2" would push both the previous entries up. You would end up with:

        0
        2
        2
        2

        Hitting "+" would add the first and second stack locations, and drop the result of the first addition from the third to the second location.

        You would then have

        0
        0
        2
        4

        Then hitting multiply would leave you with

        0
        0
        0
        8

        It was very very handy for dealing with situations like the (1+1) x (2+2) and even formulas with several more such terms, without having to carefully plan out all the parentheses if you were doing calculations on the fly, without writing everything out first..

        * I call the TI units mixed mode, because with some, like the 2 + 2 = 4 calculation, you enter things with standard arithmetic notation. But with others, like trigonometry, you enter the number first and the operator second. To get the sine of an angle, you would, even with the TI, enter the value first, and then press the "sin" button, which is actually "RPN".
        Last edited by J Tiers; 07-19-2020, 03:12 AM.
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #19
          I started using RPN calculators in varsity (HP 32S II), I have several bigger ones now but for most work still prefer the small 32. My 48GX can do differentiation and integration as well, but luckily I don't use that hated abominations anymore.

          RPN sounds complicated when you first see it, but once used to it you can work much faster and with less key inputs, especially on complex problems. The margin for error is reduced, and you can go back a few steps to correct an error without starting the whole calculation over. I will really recommend it to anyone who uses more than just the basic add and subtract functions.

          I just realised, most people who will find RPN useful, probably already use it! The downside of course is that you get so used to RPN that when you use the calc on your phone you first have to stop and think about the input sequince

          Comment


          • #20
            The first step is to admit to yourself you have a problem. You must admit to yourself you are a calcuholic. From there you must get help for a professional calcuholic therapist. The yellow pages are your friend. P.S. I am a closest calcuholic. Being mathematically challenged I need calculators everywhere. As you do I have them in every drawer.
            Location: The Black Forest in Germany

            How to become a millionaire: Start out with 10 million and take up machining as a hobby!

            Comment


            • #21
              Originally posted by Blouwildebuffel View Post
              .... The downside of course is that you get so used to RPN that when you use the calc on your phone you first have to stop and think about the input sequince
              That is absolutely true! Even as infrequent as my calculator usage is, if I pick up a regular algebraic one I'll invariably start the first calculation the RPN way.
              Lynn (Huntsville, AL)

              Comment


              • #22
                I've read that the HP 35s has the ability to switch back and forth between RPN and algebraic mode of operation. I've never tried it on mine; why would anyone want to use anything but RPN ?

                Programmability is the really essential capability in my opinion. The complexity of problems that can be handled with the very limited instruction set of the 35s is amazing.
                Regards, Marv

                Home Shop Freeware - Tools for People Who Build Things
                http://www.myvirtualnetwork.com/mklotz

                Location: LA, CA, USA

                Comment


                • #23
                  I've never used RPN, but supposedly it saves keystrokes. However, I'm not sure it does, if the following is true:

                  RPN:
                  123
                  <enter>
                  321
                  <+>
                  444


                  Non RPN:
                  123
                  <+>
                  321
                  <=>
                  444


                  Maybe it's better for more complex operations?
                  http://pauleschoen.com/pix/PM08_P76_P54.png
                  Paul , P S Technology, Inc. and MrTibbs
                  USA Maryland 21030

                  Comment


                  • #24
                    I still have a sharp little folding brown thing, lots of stuff on it I never use, my favourite was a hp I found in a bin, excellent machine
                    the office ones with paper tape and Nixie tubes are really nice
                    mark

                    Comment


                    • #25
                      Reverse Polish Notation was first used in the HP scientific style calculators. HP calculators were the "Apple" of their day and they made a big deal out of it. Perhaps it is better, I don't know. It seems to minimize the use of brackets to ensure that operations are performed in the proper sequence and the need to keep track of just how many levels of brackets you have used. But you do need to keep track of where you are in that stack thing. Fewer keystrokes? I don't know. It may depend on the problem. You can's just enter 4 and then immediately a 6 if you intend to multiply them. You will just have one 46 instead of two numbers, 4 and 6. So I think there must be a keystroke after the 4 and perhaps even another one after the 6 before you can enter the X.

                      4
                      Enter
                      6
                      X

                      vs.

                      4
                      X
                      6
                      =

                      Looks like four key strokes either way. Another Enter would tilt that key count scale away from RPN.

                      I wanted to try it out, but the HP calculators that used it were at least twice as expensive as the TI ones and even more so for the Casios of that day. So, after my first four banger, which I purchased in the 60s at about $80, I had Casios and then TIs. I have used an HP on occasion, but never owned one.

                      And yes, Marv, it is a fx-260 Solar II. Anyway I thought it was a good bargain and thought it was worth posting so that some others might also benefit.
                      Last edited by Paul Alciatore; 07-19-2020, 07:06 PM.
                      Paul A.
                      SE Texas

                      Make it fit.
                      You can't win and there IS a penalty for trying!

                      Comment


                      • #26
                        Originally posted by PStechPaul View Post
                        I've never used RPN, but supposedly it saves keystrokes. However, I'm not sure it does, if the following is true:

                        RPN:
                        123
                        <enter>
                        321
                        <+>
                        444


                        Non RPN:
                        123
                        <+>
                        321
                        <=>
                        444


                        Maybe it's better for more complex operations?
                        Yes, you are right, for more complex calcs, especially in engineering applications where you cannot use rounded off numbers, and where the result of one or two calcs a few steps back gets re-used, mixing imperial and metric values in a calc, doing multiple operations with the result of the same previous operation, correcting a mistake in a operation without doing the whole thing over, using pre-saved constants and so on. The list is endless, but you are not going to save time on one or two simple calculations.

                        I must say though, certain calculations that were page after page years ago is getting replace by increasingly affordable and in some cases even free analytical software, even for homeshop users. Calculating for example the stresses, deflections and so on in a steel member used to take hours, now I can use Fusion 360 which does a lot of that for free! I can even upload a case study to their server and download the result without bogging down my PC!

                        My wife also use HP, the non RPN financial model. She holds a MBA and a degree in corporate financial planning, so she does pretty advanced financial calculations on a daily basis, but she prefers the normal calculators, so maybe the RPN is more suited to engineering type of work.

                        Anyway, as with all things, it is not for anyone, but I believe one should be openminded to all new things, and if you don't like it, you have learned something. My grandmother always say the day you stop learning is the day you might as well roll over and die. She is 93 and runs a small sheep farm.

                        Comment


                        • #27
                          Yup calcoholic here - every "device" has an emulator on it so I've always got an HP RPN close to hand when away from the real thing at my desk. I still prefer real buttons though over touch screens and if second hand HPs weren't silly money I would have them scattered around.

                          Before true algebraic (graphic display), scientific calculators were actually a mix of direct and reverse, for example to calculate "sin( 30 )" one has to enter the argument before the function much like an RPN calculator.

                          Comment


                          • #28
                            Originally posted by mklotz View Post
                            I've read that the HP 35s has the ability to switch back and forth between RPN and algebraic mode of operation. I've never tried it on mine; why would anyone want to use anything but RPN ?

                            Programmability is the really essential capability in my opinion. The complexity of problems that can be handled with the very limited instruction set of the 35s is amazing.
                            Agree 100% with this. I've read some RPN discussions that equate the order of writing down basic math problems on paper with this notation, ie., to add two numbers, one would write down the first, then the second below it and then perform the function desired. The algebraic method, alternatively, would have one write down the first number then somehow insert the activating keystroke (+, -, x or รท), then the second number and finally the = key. This is on reason why RPN seems so very quick and easy to use, at least in my experience.

                            I still have my first HP calculator, a 29C, which I bought 43 years ago. I now use my 35C as my goto calculator though. And although the manual does discuss how the 35C can operate in algebraic mode, I can't imagine ever using it.

                            Dan
                            Salem, Oregon

                            Comment


                            • #29
                              Originally posted by Paul Alciatore View Post
                              Reverse Polish Notation was first used in the HP scientific style calculators. HP calculators were the "Apple" of their day and they made a big deal out of it. Perhaps it is better, I don't know. It seems to minimize the use of brackets to ensure that operations are performed in the proper sequence and the need to keep track of just how many levels of brackets you have used. But you do need to keep track of where you are in that stack thing. Fewer keystrokes? I don't know. It may depend on the problem........
                              The keystrokes issue is not what is best. The goodness is really in the stack and the RPN.

                              You can do a fairly complex set of terms in an equation without having to carefully plan out your set of brackets to make sure you have enough at the beginning.....

                              With "algebraic", you start at the outside of the equation and work in, and must carefully set up the brackets to work right. With RPN it is more as if you start at the middle and work your way out, and I found that one can calculate the answer more readily. I am fairly certain you can think up a case where that is not true, but in actual use, it is much more often true than not true.

                              Besides, the "algebraic" calculators are actually mixed mode.... some operations are algebraic, and some are RPN. Sqrt, Sine Cosine, etc are universally RPN, for instance, in the form <number(s), operation>. That's a "quibble" about definitions, but it is still true.

                              Some folks like RPN a lot, some don't see the point. Some people have manual dexterity, or a good visual imagination, and some do not. YMMV, some settling may occur.
                              1601

                              Keep eye on ball.
                              Hashim Khan

                              Comment


                              • #30
                                I use "Realcalc" on my smartphone. Very capable RPN calculator. And for a modest upgrade fee will give you fractions. Not affiliated with the maker.

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