|Regular HP12C and HP10C: [1/x] bug?|
Message #1 Posted by Vieira, L. C. (Brazil) on 9 Jan 2007, 6:01 a.m.
last year, a 'keyboard lock' for the HP12C was mentioned by one visitor, and I felt compelled to investigate. Right after January 1st. I got such information from a friend of a friend... and it works! At least, it gave me the expected results.
In fact, it seems to be a bug in the [1/x] routine in both the regular HP12C and the HP10C. I tested with the HP11C and the HP15C and it did not happen. I did not test the HP16C, but it seemed meaningless, as youīll see.
Exception made for the new breed HP12C Platinum and Prestige, all voyagers have the [ON]/[yx] reset ([ON]/[PMT] in the HP12C, [ON]/[D] in the HP16C), and some investigation from other contributors allowed us to know that, if I am not wrong, a nibble rotation in the x-register contents is actually what happens. So, after such [ON]/[PMT] reset ([ON]/[yx] in the HP10C), chances are that what you see in the display cannot be handled by the calculator internal routines as a valid number.
In both the HP10C and īflatī HP12C the resulting 'number' after this reset causes a sort of endless loop if the [1/x] key is pressed. Maybe the [1/x] routine in these models never reaches a return point with such arguments.
SO... if you want your HP12C (or HP10C) in a coma state for some minutes, try this:
KEEP IN MIND THAT YOUR CALCULATOR WILL NOT RESPOND TO KEYSTROKES FOR SOME MINUTES, MAYBE 10, AND THAT I TESTED THIS PROCEDURE IN, AT LEAST, FOUR HP12C AND ONE HP10C, BUT I CANNOT ENSURE THAT THE SAME BEHAVIOR AND/OR INTEGRITY WILL BE OBSERVED IN ALL UNITS!!!!
turn your calculator on;
simultaneously press [ON] [PMT] (HP12C);
you should see something like 0.00004;
Your calculator will not respond to any keystroke for some time. I guess it waits for about 10 minutes, i.e., the auto shut-off time. I do not know if this 'coma period of time' is recycled if a key is pressed, all I know is that I had to leave them resting for some time prior to use them again. Not a 'keyboard lock' as stated before, instead a 'coma' state.
There it is... I was told that people used to do this here to avoid uninvited users to take control of their beloved calculators.
Edited: 9 Jan 2007, 7:32 a.m.