Hello, Wayne;
I hope you forgive me posting instead of Eric (and I hope Eric forgive me, too), but I think there is no problem on what you're getting after you press [R/S].
I don't see Eric's listing, but there is one fact we probably agree with: unless the circuits are faulty, you can either use [RCL] or [STO] to make sure a register exists. If you use [RCL] instead of [STO], you'll change stack contents unless the register you recall the contents from does not exist. You probably have one or more [FS? 25] or [FS?C 25] instruction somewhere in Eric's program to detect the occurrence of a "nonexistent" register. When this happens, the program stops and shows a compreensive message, like "STO OK:###".
I guess you typed the program in and you did it without using any specific "synthetic" procedure, I mean, only regular keystroke sequences. So I must tell you that the HP41 has a "standard" behavior when you run a program: the program becomes the "current" program. if you run a program and right after it stops you press [PRGM], you'll see something like this:
[00 .REG. ### ] (if you press [SST] you can navigate)
or
[ PRIVATE ] (protected program; can't navigate)
or
[00 ] (ROM program; can navigate but alter)
It's not unusual to start running a program and stop somewhere else; in this case, you can also see a step number and some mnemonics after pressing [PRGM], meaning the program actually stopped somewhere but the last step (an END). The fact is that the "current" program is completely available to be edited if you press [PRGM] (unless it's a protected program or a ROM program). The best procedure to position the "calculator" (i.e. program counter) in an unused part of the available memory is pressing:
[GTO][.][.]
after you finish using any programs. You might do that only when you are not running programs taht compuse a particular computation that's still being performed at the moment, because [GTO][.][.] sets some internal pointers to default condition, and also clears some internal references like subroutine return addresses, if applicable (and if I am not wrong...). If you are in the middle of some particular computations with the use of programs AND you need to briefly stop, don't use [GTO][.][.]. You'll probably need to start over or find some mid point to continue. In
most cases, switching the calculator to OFF and back to ON later to continue where you stop without the need to start over is enough and safe.
Sorry writing too much. I think that as a beginner, you must go for the most common cases and then getting deeper into particular ones. I hope I did not confuse you much.
Luiz (Brazil)
Edited: 31 Mar 2004, 12:01 a.m.