Pi Approximation Day

[C.Ret]

(07-23-2022 11:44 AM)J-F Garnier Wrote:  

(07-23-2022 01:20 AM)Valentin Albillo Wrote:  Set FIX 6 and then run on your HP-42S (physical or virtual) this little piece of mystery code I've hastily concocted and see what you get:

01 LBL "?"
02 10
03 STO ST Y
04 LBL 00
05 RCL ST Y
06 RCL× ST Z
07 RCL+ ST Z
08 RCLx ST X
09 RCL× ST L
10 1/X
11 -
12 DSE ST Y
13 GTO 00
14 SQRT
15 END

Wonderful little program!

I'm trying to fit it to my HP-41C, but I must have missed something. Especially at step 09 RCL× ST L; where is the LAST register initialized on the first pass? Why isn't this a problem regardless of what is previously stored in the LAST register? Is this a specific HP-42S trick, does memory recall arithmetic modify the LAST register?

I'm stuck; need a little more beers to drink and any good advice to hear !