OS_Prt, send character directly to printer filter

RST 20H, DEFB $24

IN:

     A = character to be written to printer filter

     Fc = 0

     Fc = 1
     A = error code:
          RC_ESC ($01), escape detected
          RC_WP, write protected

     ..BCDEHL/IXIY same
     AF....../.... different

It is generally preferred to open a channel to the printer filter and use the usual routines.