HP-12C gets 'Entry-RPN' or Error in the QSG?

[Les Bell]

(07-05-2014 09:44 PM)Joe Horn Wrote:  Why do you say you disagree when we are saying exactly the same thing? To wit:

I think we're in a tangle because the whole thing is so badly written, and fails to provide any explanation of why you'd want to press ENTER in the first place. You see, for anyone who knows what ENTER does, it would never occur to them to press ENTER between an operation and a number in the first place - so it's an explanation of an unnatural act.

An ENTER in that position is only "optional" in the sense that it disables automatic stack lift, so that after copying X into Y, the contents of X are over-written by the entered number. But if you just go ahead and start to enter the number anyway, the automatic stack lift preserves everything, with the previous X now in Y and the new number in X.

So, the original HP text - "Pressing ENTER is optional after entering a number, if the next key pressed is an operation." - is unclear and emphasises the wrong concept: the next thing to happen. The focus should be on what's happening now - number entry - and how you tell the calculator the number is ended. I would have written, "When entering a number into the calculator, you can end the number by pressing ENTER - especially to separate it from the next number - or just press an operation".

I suspect the automatic disabling of stack lift is only there to simplify life for those who get a bit over-enthusiastic with ENTER; experienced RPN users probably rarely trigger it.