Advice with HP41 Card Reader


I recently purchased a card reader for the HP41, so am fairly ignorant as to exact operational details, and so ask for some expert advice.
I assume that when one writes a program to a magnetic card, the reader looks for a LBL and then an END and records that as a program. So if I had a short program, say only a few lines, the program will be stored on track 1 leaving lots of empty registers on that track.
So am I correct in assuming that if one wanted to record say more than one short program onto track 1 (and possibly overflow onto track 2), all you have to do is remove the "END" statement from program 1, and both will be recorded, until the "END" statement of program 2?
Your help will be appreciated in understanding how this works.
Thanks John


Correct. The card reader does not depend on labels to determine what to write. It will quite happily write a program with no labels at all. It will simply right the entire program contents of the current program--that would be everything between the beginning of the program and the END.

Hope that helps.




Thanks Marwan. By the way, I asked for advice the other day on which 41 to buy, and took your suggestion and bought a 41CV and 41CX! The CX was in fairly good condition and once I cleaned the "famous" zebra strips and I/O connections of the CV, both are working great - no cracked posts. Thanks for your help.
Regards John


Glad I could help! And I'm glad you are enjoying your new toys. The 41 was always my favorite HP and I still have quite a few of them including one that I recently converted to a CL.





The procedure, as already agreed by M. Joury, is correct. You just need to keep in mind that if you remove the 'END' statement of an existing program and, as a consequence, it merges with another existing program, its functionality will be probably corrupted. In most cases, the 'END' statement also plays the role of a RTN (return of a subroutine) or a single STOP, meaning that a running program that finds the 'END' statement will either stop running or cause a return to a subroutine call (XEQ). In any case, once you remove the 'END' statement it is a good idea to either replace it with a RTN (preferable) or a STOP, so the program will respond accordingly. These additional steps will not interfere in the original program operation.


Luiz (Brazil)

Edited: 5 Apr 2012, 11:37 a.m.


Thanks Luiz. I understand your comments and intended inserting a "Dummy" label or alpha, to remind myself where to re-insert the "end" statements.
It just appeared to be a waste of space to save or record a small program on a card.
Thanks again, regards


Hi Luiz,

Good point. I guess sometimes I forget that what I take for granted is new to others.





And for the records, the removal of the 'END' as a means to merge neighbor existing programs in memory is something that is not written in the HP41 manuals, so it is something we conclude after reasoning and experimenting, right? And we never know how deep is the understanding of the reader, we can only guess. So based on the fact that the removal of the 'END' statement had already been considered, your assumption of the basic understanding of the hole process from the reader was not incorrect. It is not an excuse but I teach at the local university. And you know, teachers tend to answer questions not yet made... (not always a good strategy, though)


Luiz (Brazil)


Thanks for both your responses. Always appreciated.

BTW I am really having fun with these new toys. I received two HP67 card packs with the calculator, and busy learning about the conversion process.


Hi John,

Glad you are having fun! Try taking all those HP67 programs and rewriting them to not need any of the 67 functions that the 41 card reader provides. Usually that is pretty straight forward but sometimes it can be a little more challenging.






I think answering questions ahead of time is a great way to prevent unexpected disasters due to unexpected side effects. I wish I was better at it but I often make assumptions that when not valid can lead to confusion.



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