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Excuse me for my trivial question, but how happened that the function (calculated by an internal routine) y^x changed starting from the HP45 after to has been, on the HP35, x^y ?

I don't know about the 'official' reason, but at the time...when I was actively using both...I remember thinking the newer/45 way felt more logical within the RPN 'postfix' philosophy.
(You first enter a number, then you apply an operation to it. You don't enter the operation first, ala algebraic.)

It also seems easier (to me) when using the 1/x in conjunction with the y^x in order to do various roots of numbers, particularly if they're already on the stack as the result of a previous operation.
For instance, if I've already got a 729 on the x register, and I want to do a cube root, it's as simple as 3, 1/x, y^x, and I've got 9.

mike

(04-30-2021 08:20 PM)trojdor Wrote: [ -> ]I don't know about the 'official' reason, but at the time...when I was actively using both...I remember thinking the newer/45 way felt more logical within the RPN 'postfix' philosophy.
(You first enter a number, then you apply an operation to it. You don't enter the operation first, ala algebraic.)

mike

Thank-you for your reply, Mike, I'm agree, it's more logical (personally I've not a great experience/feeling with algebraic calculators), but usually, having to choose the first answer I give to myself is not the good one , maybe there is another reason more "official", as you wrote

(04-30-2021 08:04 PM)aurelio Wrote: [ -> ]Excuse me for my trivial question, but how happened that the function (calculated by an internal routine) y^x changed starting from the HP45 after to has been, on the HP35, x^y ?

There is a Museum somewhere they have an explanation.

Quote:The 35 is well-known for having an x^y key instead of y^x. This makes a lot of sense on the 35 since it didn't have a 10x key. If you wanted the anti-log of a number in x, you entered 10 x^y.

Günter

[quote='Guenter Schink' pid='147130' dateline='1619815752']
There is a Museum somewhere they have an explanation.
[quote]
[/quote]

Shame on me , I missed it completely, my first calculator was the 25c thank-you Günter

Interestingly, x^y makes it easier to calculate a sequence of powers, since you go from the "top" downward.

e.g.: 2^2^2^2 = 2^(2^(2^2))

On a 35: 2 ENTER 2 x^y 2 x^y 2 x^y

On a 45: 2 ENTER 2 y^x 2 x><y y^x 2 x><y y^x

Yes, I know there are other ways to do this specific example (fill the stack with 2, etc.), but you get the idea.

Shame twice on me, I wrote "starting from the HP45", forgetting that the second pocket calculator, made by HP has been the HP80, not scientific, but anyway equipped with the y"x key

I've found here another previous old discussion very interesting about that key....

Oh - that is interesting - a negative zero value!