Int 2F Fn 122F  U - Dos 4.x Internal - Set Dos Version Number To Return    [D]

   AX = 122Fh
   DX = DOS version number (0000h = return true DOS version)

Notes: not available under DR DOS 5.0 or 6.0, or Novell DOS 7
   supported by FREEVER.COM, a freeware DOS version faking TSR by Matthias
     Paul

See Also: INT 21/AH=30h,INT 21/AX=3306h,INT 2F/AX=E000h"SETDRVER"