NAME
    PRD_PRTCOMMAND -- send a command to the printer

FUNCTION
    This function sends a command to either the parallel or serial
    device.  The printer device maps this command to the control
    code set of the current printer.  The commands supported can
    be found with the printer.device/Write command.  All printers
    may not support all functions.

IO REQUEST IOPrtCmdReq
    io_Message      mn_ReplyPort set
    io_Device       preset by OpenDevice
    io_Unit         preset by OpenDevice
    io_Command      PRD_PRTCOMMAND
    io_PrtCommand   the actual command number
    io_Parm0        parameter for the command
    io_Parm1        parameter for the command
    io_Parm2        parameter for the command
    io_Parm3        parameter for the command

RESULTS
    Errors: if the PRD_PRTCOMMAND succeeded, then io_Error will be zero.
    Otherwise io_Error will be non-zero.  An error of -1 indicates that
    the command is not supported by the current printer driver.  This
    could be used to check if the connected printer supports a particular
    command (italics for example).

SEE ALSO
    printer.device/Write printer.h, parallel.device, Preferences