Most mind-blowing program for your favorite calculator

[Steve Simpkin]

(06-18-2022 04:18 AM)pauln Wrote:  

(06-18-2022 03:29 AM)Steve Simpkin Wrote:  You really could do a lot with 49 steps of program memory.

Certainly: 49 fully-merged program steps, RPN and the ability to go to an arbitrary step without declaring a label. I'm not sure how programmers were dealing without subroutines though.

Does anybody know why 49 steps and not 50? Seems like a really odd number to me.

The HP-25 had an external data chip with sixteen 56-bit registers. Each 56-bit register could hold one BCD number or 7 steps (bytes) of program memory. One register was used for LAST x, 8 for memory registers and 7 for program memory. Thes last 7 registers with 7 bytes each made a total of 49 program steps.

See the Nov 1975 issue of HP Journal for more information.
https://www.hpl.hp.com/hpjournal/pdfs/Is...975-11.pdf