NAME   
        SetAPen -- Set the primary pen for a rastport.

   SYNOPSIS
        SetAPen( rp, pen )
                 a1  d0

        void SetAPen( struct rastport *, ubyte );

   FUNCTION
        Set the primary drawing pen for lines, fills, and text.

   INPUTS
        rp - pointer to rastport structure.
        pen - (0-255)

   RESULT
        Changes the minterms in the rastport to reflect new primary pen.
        Sets line drawer to restart pattern.

   BUGS

   SEE ALSO
        setbpen() graphics/rastport.h