New 15C LE bug?


Just found some weird behaviour on the 15C LE.

Create a function, integrate it and press R/S during the integration. The display continues flashing between running and the numeric value. In my case the function was simply:

    LBL A

A second integration seemed to get confused unless I did g RTN.

- Pauli


I only get the results that you describe if a runtime error occurs, such as an overflow when the integration algorithm tries to evaluate x! above about 69. It also appears that the integration routine will never terminate automatically after a runtime error occurs on all flavors of "15C". If no such errors have occurred, a normal display occurs anytime the run is stopped with R/S.

I evaluated your integral from 68 to 69 in fix 4 display (no runtime error expected):

Machine          Result      Execution Time
HP-15C 3.9792E97 330 seconds
HP 15C-LE 3.9792E97 4 seconds
DM-15CC (48 MHz) 3.9792E97 16 seconds

Runs could be halted with R/S with no display abnormalities.

I evaluated your integral from 69 to 70 in fix 4 display (runtime error *expected*):

These runs did not terminate automatically.

Machine          Result after R/S at 400 seconds
HP-15C 5.1602E98 blinking display
HP 15C-LE 2.0638E98 then "running" blinking alternately
DM-15CC (48 MHz) 5.2069E98 blinking display

So, there is a difference between HP 15C-LE results and those of the HP-15C and the more accurately emulated DM-15CC. I think it can be called a bug in the sense that it does not reflect the response of the original HP-15C.


I didn't think about the error potential. Yes I was integrating far enough for this to impact.

The 15C blinks the display to show an error. The 15C LE isn't doing this -- it blinks using running not a blank screen. So, definitely a bug.

- Pauli


Much much worse is the bug in the original HP-15C firmware that shows up in the HP 15C-LE and DM-15CC as well.

An integration routine that continues running after any runtime error occurs, for which only a manual R/S stops the process to show a blinking display as the only sign of an error, is very stupidly designed. Without a manual R/S these 15C-type units will just continue running until the batteries are dead, I suppose.

That's really shabby work...from the mythical golden age of HP calculators.

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