(25) Resolution of the Catch Equation by a Simple Iterative Method

[rprosperi]

(01-18-2019 08:12 PM)Dieter Wrote:  I have been looking at the listing, but there are a few things I do not understand.

First, the program has 72 steps and it uses line number addressing. Is there any HP calculator with this combination of features? The mentioned HP29C or 67 can handle the program size but they use label addressing. The HP25 can only store the program up to line 48 where it stops. So I wonder what calculator this program is intended for.

I have not looked at the register use yet, but you're right that the provided code does not match any particular machine's capabilities and instruction formats. I'd speculate that the idea was to provide this generic pseudo-code to illustrate Newton's method as implemented in RPN for HP family machines. The author notes that he has an HP-25, and while he knows the 29C and 67 have more steps, he may not be aware they use labels (vs. line numbers) so he wrote out the full procedure using 25-style code.

Another possibility (this is a stretch, but feasible) is that his intention was for part of the problem solution to be run from the HP-25 via program execution, while subsequent parts are accomplished via manual keystrokes. Notice that line 48 is a [R/S] (so this much fits in a HP-25 program) and the only GTO statements after this are to 00 (i.e. to stop), so perhaps he ran the program, and when it ended, continued the solution with manual keystrokes. Just speculating, and it does seem this would have been mentioned if it were the case, but assuming his logic is correct, it would work.