HP Forum Archive 01

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HP-15C key sequence Message #1 Posted by donaldg on 7 Apr 1999, 1:41 p.m. Try this on a 15C: Hold down "-" while hitting "ON" (this will clear all of your memory). With Pr Error displayed, turn the calc off. Turn it on again, press "4" and turn it off again. Now hold down the square root key (upper left) while turning it on, and turn it back off, 5 times. Display should read "b 0 0". Hit "+". Some program runs, and the display reads "A 0 0". Now press and hold "+" or "-" for about 5 seconds. Display reads "null" like a 41 would. I don't know what good any of this is, but it's weird.

Re: HP-15C key sequence Message #2 Posted by Paul Brogger on 7 Apr 1999, 5:44 p.m., in response to message #1 by donaldg I tend to think of my preoccupation with HP calculators as a point of distinction, a matter of pride, a highly specialized hobby. However, I'm beginning to wonder . . .

Re: HP-15C key sequence Message #3 Posted by Mark Hardman on 8 Apr 1999, 11:23 a.m., in response to message #1 by donaldg It appears that the "hard reset" (ON-) is not necessary. Also, the same result can be acheived by pressing (ON-y^x) 5 times. Other models/values yeild strange display results but never enter this strange "b 0 0" mode. Mark Hardman (led)

Re: HP-15C key sequence Message #4 Posted by orbital1 on 9 Apr 1999, 12:01 a.m., in response to message #3 by Mark Hardman it appears to be activating the matrix mode, for unknown reasons. the a......0.0 and b......0.0 are normal matrix operation displays, as is the null indicator. other voyagers lack this feature and give different results.

Re: HP-15C key sequence Message #5 Posted by Jeff Woolsey on 29 May 1999, 2:33 a.m., in response to message #1 by donaldg Looks like you've stumbled upon the window into the machine's guts... See http://www.jlw.com/~woolsey/15Cnotes.html for details.

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