> What does the "~" mean when used in the following way?
>
>  ANDLW   ~SWITCHLINES    ; keep unused outputlines from PortB
>
        generally, the "~" (tilde) means the bitwise negation
        of its operand. contrast to "!" which generally
        means logical negation. (I am assuming they mean the
        same as in ANSI-C).

        bitwise negation, of course, means negate all the bits.
        so you make all 1's into 0's, and all 0's into 1's.
        a.k.a. the 1's complement.

        -Phil