> What I don't understand is why the assembler didn't throw an error if
> incf W,0 isn't allowed.

        Where does it say it ISN'T allowed? It is certainly allowed, it just
doesn't do what you expect. incf W, 0 will assemble without issue. The
reason is 'W' is simply a constant while assembling, the preprocessor simply
replaces 'W' with it's numerical value (0 IIRC), so the assembler actually
sees: incf 0, 0, a perfectly valid opcode. Now, you could say that Microchip
could have added something in the assembler to catch these sorts of things.
The problem is that is a slippery slope for them, where does the "babying"
end? TTYL

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