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

[Dieter]

(01-16-2019 08:47 PM)SlideRule Wrote:  A typical listing of this program for HP programmable pocket calculators is presented in Table 1. Depending on the model of calculator used, all or parts of the program may be performed automatically …
With the model HP-25 calculator used by the author, parts (2), (3) and (5) are performed with the program, while parts (1) and (4) must be done manually, but the whole computation is possible in a single program with models HP-29 or HP-67. The program occupies a small number of program steps and a small amount of memory.

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.

Looking at the code it seems that several input has be be prestored in various data registers, eg. R0, R1 and R5 which hold the error tolerance. Also there must be a value in R3 before the iteration starts. The program stores such a value in line 62 and 71, but this part of the program does not fit into the HP25's 49 step memory. All in all I do not see any instructions on how to store some initial values into the mentioned registers. But without doing so the program cannot run correctly.

To me it looks like a value for M has to be stored in R0, an initial value for F in R1, the desired tolerance in R5 and finally a value for N in R3. The latter may instead be calculated by the last part of the program. But I do not see any instructions for all this in the PDF document.

Dieter