The 45 with a 15C twist


Hello all,

I've read in John A. Ball's bible, "Algorithms for RPN Calculators" that some early 45s had Recall Arithmetic exactly like the 42S and 15C. Does anyone have the serial number run of these 45s?


Edited: 4 Apr 2012, 5:24 p.m.



HP has not been consistent in implementing RCL arithmetic in all of its calculators. This feature appears in some models but not others.



Yes, as per the book, it mentions how earlier models have the feature but later versions do not.


It's fun to use the museum's calculator compare feature 2 c this.


I've been using that quite a bit lately. Very handy. Quite informative.


All HP-45's had Recall arithmetic like the 42S and 15C. The difference between early and later models was in Store arithmetic. In early models, STO-n would subtract the value in register n from the value in stack X, and store the result in register n. Similarly, STO/n would divide the value in register n into the value in stack X, storing the result in register n. In later models, STO-n would subtract the value in stack X from the value in register n, and STO/n would divide the value in stack X into the value in register n. As for when the change occurred, I have a version 1 (with the raised metal bar at the top of the keyboard instead of the silver trim), S/N 1301A04xxx which has the former behavior and another, S/N 1350A89xxx which has the latter. I know that there are serial numbers which begin 1349 that also have the later behavior. I have no knowledge of other S/N series numbers and do not know when the change-over occurred.

Edited: 6 Apr 2012, 11:38 p.m.

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