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I seem to have two different versions of the HP-45. On one of them the sides run around the perimeter of top with no variation but on another, at about halfway down the screen, there's a bevel in the plastic on both sides. Is one earlier or rarer than the other?

If it's like my HP-45 the bevels are wear marks from carrying the calculator in the optional hard leather belt case. I paid more for my 45 than I did for a quarter's registration fees at UC Berkeley, so during my years at Berkeley the calculator was either in the hard case on my belt or in my hands. I dug a lot of ditches to pay for that machine, and I still have it (and of course it still works).

As indicated the bevels may be worn marks. However I have 2 different types of 45s.
One comes with a metal bar below the screen instead of chrome plating. On this one ON/OFF is printed in yellow.
The other does not have the metal bar and is chrome plated all around and has ON/OFF molded in the brow plastic.

I however don't know if there are some molded on/off with metal bar or some printed on/off without the metal bar

Arnaud

On the firmware side, there were at least two variants of HP 45, which differed in the operand sequence for recall arithmetic.

For instance, if Register 1 contains a 5 and the X register contains a 3...

In some calculators, RCL - 1 gives 2 (i.e.: X - R1 -> 5 - 3)

In others, RCL - 1 gives -2 (i.e.: R1 - X -> 3 - 5)

The same change of order affects division, of course, there si no difference for addition and multiplication.

"The same change of order affects division, of course, there si no difference for addition and multiplication."



What about LASTX ?

[VPN]

We were talking about recall arithmetic, which avoids stack lifts. As one of the arguments is still in one register (say R1), the only reasonable use of Last X is to hold the previous X value (the one before the recall artitmetic operation), independently of order.

Sadly, I don't have a 45 on hand to check this out.

VPN:

At least in the HP42S (the only recall arithmetic enabled model I have on hand) the behavior of LastX is just to keep the previous X value, so there is no order issues for Last X in recall arithmetic.

Regards