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Hi all.

Given that the HP-25/25C has a LastX register and function, why was LastX omitted from the 21?

Thanks

(03-04-2021 04:04 AM)Matt Agajanian Wrote: [ -> ]Hi all.

Given that the HP-25/25C has a LastX register and function, why was LastX omitted from the 21?

Thanks

The 21 came out before the 25's, and was similar in functionality to the 35. There is no external memory in the HP-21, only the registers in the ACT, one (M1) is the single memory location, the other (M2) register is for scratchpad use during calculations, the 6 others are the stack and display/scratchpad use.

cheers

Tony

Thanks for the details. I didn’t realize that after the stack, scratchpad, and display, there was nothing left for a Last X reg.

HP-70 don't have LSTx too.

Gamo