Re: 10 Key Calculators vs RPN Message #3 Posted by Paul Berger (Canada) on 26 Mar 2011, 10:29 p.m., in response to message #1 by Matt_12c
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 HP97 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.
