HP-41CX Bug?


Hi All,

Using my HP-41CX, I happened to execute CAT IND followed by the decimal and a stack register name (such as X or Y), expecting the command to use the value in the references stack register. Instead the calculator behaved like I entered CAT 0. Is this a know bug? Is it a bug at all? Am I missing something?



My HP-41CX exhibits the identical behaviour, V41 too. If I put 2 into register 00 for example, CAT IND 00 performs CAT 2. If I put 2 into a stack register (any of them), CAT IND ST X (or Y or Z or T) performs CAT 0. Strange.

Another interesting thing: i41CX+ does not allow CAT IND. When CAT is pressed, it comes out as CAT' and SHIFT key is ignored after that.

Edited: 5 June 2009, 6:22 p.m.


Regarding the I41CX and CAT ' , you probably have CCD installed. Without CCD, it does allow you to enter CAT IND etc.



Nigel, I believe that you are wrong. I have an HP-41C (early, all bugs version), an HP-41CV 'fullnut', an HP-41CX 'fullnut' and an HP-41CX 'halfnut'.

All four instruments allow me to execute a CAT IND X, with no modules of any kind installed.

The result is the same for all of them, regardless of what resides in the X register. The HP-41 executes a CAT 3.



Got any modules installed? ZenROM, CCD, and maybe other ROMs affect the way "partial key sequence" entry works.


I have the IR printer module and an X-Mem module in my HP-41CX.


You're right. After I removed CCD, Advantage, Math, and PPC modules, I now can execute CAT IND. However, as stated in a post below, the bug appears to be identical to the one on V41 and real HP-41.


If memory serves me correctly, this 'bug' has been documented in at least one of the popular '3rd party' HP-41 books (Extend your HP-41?) It exists in all the HP-41 versions. It was omitted from almost all 'bug lists' because it was inconsequential. There was no real application for CAT IND (X-T), (CAT is not programmable) so the design and engineering effort was never expended by HP to 'fix' it.



Thanks Dan. I just wanted to know if I was just "re-visiting" a previously known bug.


Edited: 7 June 2009, 4:44 p.m.

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