10 Key Calculators vs RPN


Hi, I'm new to the HP calculators. I am in a graduate accounting program after having graduated with my BS in the mid '90s. I decided I wanted a business calculator, preferably that acted like a 10 key so I researched what was popular. Imagine my amazement when I found that the HP 12C was still a major player! I remember being a "poor college student" back in the '90s wishing I could get a 12c but settling for a weak Casio, that didn't have business functions and barely handled stats! Not to mention that I went through hard core finance classes with it. I digress but I'm sure someone can relate.

So I get a 12c (a nice Malaysian one). I'm curious - what is the difference between 10 key calculators (ie tape calculators) and RPN? They are obviously related somehow. I initially wanted a tape calculator because of what I always thought was RPN, and its fast ability to enter a column of numbers. The business functions of a 12c would be great but I really wanted a portable calculator that was like a 10 key. Why is it that you can buy a 10 key with tape, but can't buy a calculator that operates like a 10 key but not tape (ie compact and portable)? I'd think it would be easy to put one out. I get the whole seeing the tape thing but that's not crucial.

I thoroughly enjoy using my 12C but I'm curious how they are related, and why there doesn't seem to be any such thing as a 10 key without tape! One other thing - I get using the enter key for HP to either fill the stack or for basic operations, but why would a person not want to just enter 5 + 5 + to get 10 rather than 5 ENTER 5 +.

Hope this makes sense.


Edited: 26 Mar 2011, 8:05 p.m.


"5 + 5 +" would work just fine so long as the Y register initially contained zero. In practice, it's not necessary to clear anything [on the stack] prior to starting a new calculation with an RPN device, so the safest bet would be "5 ENTER 5 +". The ENTER key is really only necessary to separate two subsequent numeric entries; those which don't require any other operations being performed on the first one. That is to say, if you'd enter "25 square-root 5 +", or "0.2 '1/x' 5 +" it'd not be necessary to use the ENTER key at all.

I can't begin to comment on the other aspect of your topic...

Edited: 26 Mar 2011, 8:53 p.m.


They are quite similar for functions like adding a column of numbers, in both cases you can add up the numbers by entering the number and press the + key, there are however some differences in operation.

On a 10 key machine if you where not sure that the accumulated total was cleared you would press the total key and it would print what ever the accumulated total was and then clear it. Most modern "10 key" machines also have an electronic display that shows you the number as you enter it and also displays the running total after you press the plus key. You enter positive numbers by pressing the + and negative numbers by pressing - key. As you enter the number it goes into a temporary register and when you press the function key the number is added or subtracted from the accumulated total. When you are finished with a column of figures you would press the total key, and the accumulated total would be printed on the tape and the accumulated total is cleared automatically.

On a HP RPN calculator with a one line display, it is always showing you the contents of the X register which would be similar to the accumulator on the 10 key machine. When you start to enter a number the value in the X register gets pushed up to the Y register and then when you press the plus or minus key the value in X will be added or subtracted from the value in Y and the result will be placed in the X reg, sounds very much like the 10 key so far, so here are the differences. When you start to enter a column of figures to make sure you don't end up inadvertently adding to a value that is already in X, you can either press the "clear X" key that most RPN calculators are equipped with or you can press enter after the first number. Pressing enter forces the number you entered to remain in X without having anything else done to it. I am not aware of any HP RPN calculators that have a total key, but like the 10 key machine after you press the function key the running total is displayed.

If you have a model that has printing capabilities, like the HP-97 that sits beside me at my desk, with the printer in normal mode it prints the numbers as entered, and the LED display shows the number as entered, and the running total after the function key is pressed, just, like the 10 key machine, however to print the total on the tape I need to press the "print X" key, but that does not clear the accumulated total from X, however since my 97 is programmable I could easily program it to emulate a 10 key machine if I desired.


<pre> You could simulate some basic 10 Key operations by using the Statistics keys:

f CLEAR SIGMA (SST key) clears the Stat registers or "clears the tape"

number SIGMA+ (similar to the + key on the 10 Key) - the calculator displays the item count

To subtract: number CHS SIGMA+ (do not use SIGMA- because it will erase the last input)

Total: RCL 2 - this is similar to the S* key because you can continue an addition. There is no 10-Key T key so to start a new calculation you have to start over (f CLEAR SIGMA)

Item Count: RCL 1

I think this works on the all of the HP RPN calculators, but storage registers used for statistics very with each model. The registers on this post are specific to the HP 12C.


I wonder about the HP Printcalc 100. Does that possibly act like a 10-key calculator? It is fairly compact compared to most 10-keys.


Well, compared to my 10 key that HP is tiny. It's missing some keys that my 10 key has but I bet I could get use to it. Sorry. No direct experience with it so I'll sit back was read. ;-)


A 17bii+ Silver with an 82240A or 82240B IR printer would do what you suggest. While the 17bii++ series is not as fast as the 12C, it is much more capable and memory is more spacious. Together with the utility of printing, that's the best you're going to get with RPN+tape.

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