BigStack RPN Calculator

Nice but know that the action of the Enter key is different from nearly all other RPN calculators. Everywhere else, "Enter" moves the stack up but also leaves a copy of the x register in the x register. This calculator deletes the x register. So if you type "2 Enter +" on this calculator you get an error, where every other RPN calculator I've seen would give a result of "4".

First of all, thanks for the feedback. Good or bad, it's all welcome.

To answer the question directly though, the Enter key is working correctly.

On the older model HP RPN calculators, like the 11, 12, and 15 series, there was only a single line of the stack shown in the display. So HP made the decision to keep showing the value you had entered after you pressed the Enter key until you pressed some other number and then it would be replaced by the number you had typed. HP made this decision because they were only showing a single line of the stack and the alternative was to show nothing, or zero, once the Enter key was pressed. And this would have confused people.

If you look at a newer model of an HP RPN calculator, like one of the 28 series, where there are multiple lines of the stack displayed at once, the Enter key no longer behaves this way. When you press Enter, the value you have entered so far is put onto the stack and the entry area is cleared. So on an HP 28-S for example, pressing "2 Enter +" would give an error, just as it does on the BigStack RPN calculator.