INT 21 - DOS 3.2+ - IOCTL - GENERIC CHARACTER DEVICE REQUEST
        AX = 440Ch
        BX = device handle
        CH = category code
            00h unknown (DOS 3.3+)
            01h COMn: (DOS 3.3+)
            03h CON (DOS 3.3+)
            05h LPTn:
            9Eh Media Access Control driver (STARLITE)
            00h-7Fh reserved for Microsoft
            80h-FFh reserved for OEM/user-defined
        CL = function
            00h MAC driver Bind (STARLITE)
            45h set iteration count
            4Ah select code page
            4Ch start code-page preparation
            4Dh end code-page preparation
            5Fh set display information (DOS 4.0)
            65h get iteration count
            6Ah query selected code page
            6Bh query prepare list
            7Fh get display information (DOS 4.0)
        DS:DX -> (DOS) parameter block (see below)
        SI = parameter to pass to driver (European MSDOS 4.0, OS/2 comp box)
        DI = parameter to pass to driver (European MSDOS 4.0, OS/2 comp box)
Return: CF set on error
            AX = error code (see AH=59h)
        CF clear if successful
            DS:DX -> iteration count if CL=65h
            SI = returned value (European MSDOS 4.0, OS/2 comp box)
            DI = returned value (European MSDOS 4.0, OS/2 comp box)
        DS:DX -> (OS/2 comp box) data block
Note:   bit assignments for function code in CL:
                bit 7: set to ignore if unsupported, clear to return error
                bit 6: set if passed to driver, clear if intercepted by DOS
                bit 5: set if queries data from device, clear if sends command
                bits 4-0: subfunction
SeeAlso: INT 2F/AX=0802h,INT 2F/AX=122Bh,INT 2F/AX=1A01h

Format of parameter block for function 00h:
Offset  Size    Description
 00h  8 BYTEs   ASCIZ signature "STARMAC"
 08h    WORD    version
 0Ah    WORD    flags
                bit 0: media requires connect or listen request before use
                bit 1: network is a LAN (broadcast/multicast supported)
                bit 2: point-to-point network
 0Ch    WORD    handle for use with MAC driver's private interface (filled in
                by MAC driver)
 0Eh    WORD    context
 10h    WORD    approximate speed in KB/sec (filled in by MAC driver)
 12h    WORD    approximate cost in cents per hour (filled in by MAC driver)
 14h    WORD    maximum packet size in bytes (filled in by MAC driver)
 16h    WORD    addressing format (filled in by MAC driver)
                0000h general addressing
                0001h Ethernet addressing
                0002h Token Ring addressing
                0003h Token Bus addressing
 18h    DWORD   Send entry point (filled in by MAC driver)
 1Ch    DWORD   RegisterEventHandler entry point (filled in by MAC driver)
 20h    DWORD   SetPacketFilter entry point (filled in by MAC driver)
 24h    DWORD   UnBind entry point (filled in by MAC driver)

Format of parameter block for function 45h:
Offset  Size    Description
 00h    WORD    number of times output is attempted before driver assumes
                device is busy

Format of parameter block for functions 4Ah and 6Ah:
Offset  Size    Description
 00h    WORD    length of data
 02h    WORD    code page ID
 04h 2N BYTEs   DCBS (double byte character set) lead byte range
                  start/end for each of N ranges (DOS 4.0)
        WORD    0000h  end of data (DOS 4.0)

Format of parameter block for function 4Dh:
Offset  Size    Description
 00h    WORD    length of data
 02h    WORD    code page ID

Format of parameter block for function 4Ch:
Offset  Size    Description
 00h    WORD    flags
                DISPLAY.SYS = 0000h
                PRINTER.SYS bit 0 clear to prepare downloaded font, set to
                        prepare cartridge selection
 02h    WORD    length of remainder of parameter block
 04h    WORD    number of code pages following
 06h  N WORDs   code page 1,...,N

Format of parameter block for functions 5Fh and 7Fh:
Offset  Size    Description
 00h    BYTE    level (0 for DOS 4.x and 5.0)
 01h    BYTE    reserved (0)
 02h    WORD    length of following data (14)
 04h    WORD    control flags
                  bit 0 set for blink, clear for intensity
                  bits 1 to 15 reserved
 06h    BYTE    mode type (1=text, 2=graphics)
 07h    BYTE    reserved (0)
 08h    WORD    colors
                   0 = monochrome
                   else N bits per pixel
 0Ah    WORD    pixel columns
 0Ch    WORD    pixel rows
 0Eh    WORD    character columns
 10h    WORD    character rows

Format of parameter block for function 6Bh:
Offset  Size    Description
 00h    WORD    length of following data
 02h    WORD    number of hardware code pages
 04h  N WORDs   hardware code pages 1,...,N
        WORD    number of prepared code pages
      N WORDs   prepared code pages 1,...,N