Apple extended keyboards do not have a Num Lock on them, at least the ones I have don't, which means that they just work.
After all, on an Apple extended keyboard there is nothing on the number pad except numbers and math symbols so why would you need to turn it on and off.
Third party Mac key boards may have a Num Lock which, I guess, functions in the same way as a keyboard on a PC.
I don't see anything in the System Preferences/Keyboard that relates to this problem or a Keyboard preference file
P
The numbers lock on my old keyboard quit. I just purchased any new extended keyboard and that doesn't work either. I am using a Mac Pro 2 x3 GHz Quad-Core Intel Xeon.
What's the trick for the getting extended keyboard to lock.

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