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Comment by 7thaccount | Hacker News Reader

No, HP calculators were more efficient it would seem with their RPN.

"20 ENTER 8 ENTER - 7 ENTER +"

So you push 20 onto the stack and then 8 on the stack. Then you hit the minus key which returns 12 and puts that 12 on the stack, then you put 7 on the stack and click the plus key to give you 19.

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That will give you 20 0 14 on the stack (top to the right). After 20 ENTER 8 ENTER you have 20 8 8 on the stack (and the stack lifter disabled). - gets you 20 0; 7 ENTER gets you 20 0 7 7 (and the stack lifter disabled again); + gets you 20 0 14. If you want to compute 20 - 8 + 7, type 20 ENTER 8 - 7 + . As another comment points out, you only use ENTER to separate two numbers. Other ENTER:s are not optional, they are usually downright wrong, unless duplicating the number at the top of the stack is what you want. (Edit: as I am mentioning the stack lifter, I should probably say "bottom" rather than "top". The HP calculator stack was usually visualized as being above the display, with operations taking place at the display, i.e. at the bottom of the stack.)

Per what you say, it takes 9 key presses on HP and 8 key presses on a soviet to calc same expression. Which one is more effient ? ;)

You only need the first ENTER to separate the numbers; the rest were optional:

"20 ENTER 8 - 7 +"

Not in general, I guess; 20 - 8 * 7 would be "20 ENTER 8 ENTER 7 * -". So if you need to do first operation which is not the leftmost, you'd have to add another "ENTER".

7 replies in from my (downvoted) original post and people are still arguing about syntax.

I rest my case

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