INT 21 - DOS 1+ - CLOSE FILE USING FCB
AH = 10h
DS:DX -> File Control Block (see AH=0Fh)
Return: AL = status
00h successful
FFh failed
Notes:  a successful close forces all disk buffers used by the file to be
written and the directory entry to be updated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=16h,AH=3Eh

See also: 210F

2110 - DOS 1+ - CLOSE FILE USING FCB