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The article links to this explanation of RPN and its benefits. https://www.swissmicros.com/what_is_rpn.php https://www.swissmicros.com/what_is_rpn.php After re

• tzs 9y ago
  For iPhone, PCalc [1] is quite good. It's also excellent on iPad. In fact, when my iPad 3 was due for replacement, PCalc almost persuaded me to go with iPad Pro instead of switching to a Surface Pro 4, but the SP4 won for better web browsing, better copy/paste, and OneNote. The MacOS calculator's RPN mode is annoying. They don't get stack lifting right. Suppose you want to compute sqrt(12) + pi. Starting from an empty stack, this will do it on an HP calcualtor, PCalc, both RPN calculators I downloaded from the Windows Store, and, well, pretty much every RPN calculator I've used except from Apple: 1 2 SQRT Pi + When you hit the Pi key, it pushes Pi onto the stack, lifting up the sqrt(12) that is already there. On the MacOS calculator, the Pi overwrites the sqrt(12). If you do it this way: 1 2 SQRT 3 . 1 4 1 6 + then it works the same everywhere. One other difference to watch out for. On some calculators, this: 2 ENTER + will give 4. This includes some HP calculators, such as the HP-15C. On these calculators the ENTER pushes whatever is in X, and leaves a copy in X with a flag set telling it that if you enter more digits they should overwrite X. Number entry goes directly into X, so the "2" goes into X, the ENTER pushes X to Y, so now X = 2 and Y = 2. So "+" works, giving 4. On others, it will give a missing operand error. This includes the HP-48 family. On these calculators, number entry does not take place in X. It takes place in some sort of input buffer, and ENTER pushes that onto the stack so it ends up in X. So the "2" goes into the input buffer, ENTER signifies you've finished and 2 goes to X. X was empty before so nothing gets pushed to Y. So you've only got one operand and the "+" fails. (On these calculators, operators other than ENTER implicitly insert an ENTER first if the input buffer is not empty). I'm not sure why HP changed this. The older calculators only had 4 stack positions, no entry buffer, and the display only showed X. By the time of the HP-48 they had many many more stack positions, an entry buffer, and the display could show the bottom 4 stack positions (or the bottom 3 and the entry buffer during digit entry). Perhaps the HP-48 behavior is what they always wanted, but decided it would be too confusing on the older calculators where your visibility was limited. PCalc and MacOS calculator are like the HP-15C. PCalc has an "HP 48 Style" option on the advanced settings page if you prefer the HP-48 behavior. [1] http://www.pcalc.com/ http://www.pcalc.com/
• Fwirt 9y ago
  The firmware for the DM42 is based on GPL'd software available for all major operating systems (including iOS.) http://thomasokken.com/free42/ http://thomasokken.com/free42/