> I found some lines of code which don't make any sense. I got one line
>                 TRIS    PORTC
> The 16C58A does not have a PORTC, so how come I got a TRIS for that port?

Perhaps an earlier version of that product (maybe a development proto) used
a 16C57 and consequently had a PORTC (which the programmer could use for
outputting diagnostics).  While the 16C58 no longer has a PORTC, the prog-
rammer may have left in the diagnostic code from before (since leaving it
in is less likely to change the program's operation than taking it out).