INT 21 - DOS 1+ - RANDOM BLOCK READ FROM FCB FILE
        AH = 27h
        CX = number of records to read
        DS:DX -> opened FCB (see AH=0Fh)
Return: AL = status
            00h successful, all records read
            01h end of file, no data read
            02h segment wrap in DTA, no data read
            03h end of file, partial read
        [DTA] = records read from file
        CX = number of records read (return AL = 00h or 03h)
Notes:  read begins at current file position as specified in FCB; the file
          position is updated after reading
        not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=28h,AH=3Fh