HP-41CV "private" program


I just recently turned on my HP-41CV, and heard two beeps before it turned on. When I went into program mode, the display showed PRIVATE. In this mode, it did not allow me to enter any program steps. Has anyone ever seen this strange behaviour before? I had to do a reset before the calculator returned to normal.


The card reader can be used to make programs private so they are not editable. Somehow the internal flags must have been set to make your whole calc private. There were tricks to getting around private programs detailed in PPC mags and the like.


In previous threads here at the Museum, and (if memory helps) in the articles forum, there are explanations about Private programs and how to un-private a program so protected by accident. The idea of Private mode was to protect the program code from scrutiny, copying or alterations, while allowing full use of it. There are few other ways in which to protect code when the source code is loaded in RAM and interpreted at run time, as in a calculator. On a computer you may distribute compiled and linked executable code without risking the source code.

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