HP 25 Fibonacci sequence in one program step

[Gerson W. Barbosa]

(10-13-2021 08:34 PM)rprosperi Wrote:  Many other models support recall arithmetic (45, 27, 15C, 32S, 32SII, others?) but only the 42S includes recall arithmetic AND stack register access.

Since we’re at it, I decided to write an HP-42S program to display the Fibonacci sequence trying to use the least number of steps (Not sure whether I’ve succeeded or not – another one I tried has exactly the same number of steps and bytes). Interestingly an equivalent HP-15C program, which lacks recall stack arithmetic but does have recall arithmetic, is possible using the same number of steps (8).

Code:


00 { 20-Byte Prgm }
01▸LBL "Fib"
02 2
03 -1
04 +
05▸LBL 00
06 RCL+ ST L
07 STOP
08 GTO 00
09 END

XEQ “Fib” → 0
R/S → 1
R/S → 1
R/S → 2
R/S → 3
R/S → 5
R/S → 8
…