UNDOing Program deletion


I perused the manual but I don'think it specifically says this (although it may be in there somewhere). Experimenting with the UNDO key, I discovered that if you CLEAR a program label in MEM (ie. delete a program) the UNDO key will retrieve the program. The manual states it can UNDO a line of program, register, equation, or cleared value, but not specifically an entire program. FYI.



Whoa! If that's true, that's a big plus! Great find.



Seems to be true! Note that it can only do this if you haven't yet left the program list, and haven't deleted another program. I suspect that the program isn't actually deleted until you perform one of these other actions, and hence it's easy to undo.

Good feature!

I wonder if there's a way to UNDO the lack of R->P and P->R keys? :-)



Now that would be nice trick. ;)


You can UNDO *anything* immediately after a CLEAR. Even an UNDO after a CLEAR ALL works. All programs, memories, equations the stack and the program pointer come back! The only thing that you can do between a CLEAR and a successful UNDO is turn off the calculator and turn it back on, anything else will void the UNDO.


Interesting. A virtual delete followed by a commit later, huh? ;-)

Thanks for experimenting and finding the limit, Katie. I have to say, this would seem to be a key feature that HP should highlight better in the manual. Maybe there's a resistance to become "liable" for mistakes, but wow, being able to UNDO a CLEAR ALL is a hugely important feature that shouldn't be glossed over.

Reason: I tend to memorize a lot of the 33s/35s style of choice menus such that I just hit the appropriate number key instead of navigating to the item and hitting ENTER. Let's say I'm not at the top of my game today, and I go to the CLEAR menu, planning on clearing all the stats registers, but then find that I've hit 2 instead of 4 -- clearing the variables instead of stats. It is a great feature to know that I can do an UNDO and get them back!


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