On Wed, Jun 18, 2025, 1:32 AM Jerome Shidel via Freedos-devel < freedos-devel@lists.sourceforge.net> wrote:
> > It looks interesting. > > But, I think I have know idea on how to use such a calculator. > > I tried entering “12-5” and got -7 as the answer. Probably me. > > ;^/ > That is the correct result for an RPN calculator if you did what I think you did. RPN operates on a stack with operators. So to calculate "12-5" you'd enter: 12 <enter> 5 - Typing "12 <enter>" puts the number 12 into the stack. Typing "5" puts the number 5 into the stack as the next value. And typing "-" performs the action to subtract the two values in the stack: the first number minus the second number, or 12 minus 5, which gives 7. But if you entered the numbers like you might in a standard calculator, you probably entered: 12 - 5 And if you start with nothing (zero) in the stack, the "-" is the action, so that's the same as "0-12" so now you have -12 in the stack. Entering the "5" puts 5 on the stack, and if you happened to hit "+" after that (that's what I think happened) then that adds the two values on the stack, which is the same as "-12 + 5" which gives -7. So you got the right answer for what you entered. I'll add that RPN is not my preferred way to use a calculator, but I know a few folks who love it so I've learned the basics of RPN just by osmosis. :-) >
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