Note: This API call is for DOS and Win16 personality only. Use Family API for portability.

2018/09/07 05:04 · prokushev · 0 Comments

Int 21H, AH=5cH, AL=00H


3 and higher


lock region of file

Family API


AH = 5Ch
AL = 00h lock region of file
BX = file handle
CX:DX = start offset of region within file
SI:DI = length of region in bytes


CF clear if successful
CF set on error
    AX = error code (01h,06h,21h,24h) (see #01680)



error returned unless SHARE or network installed
an unlock call must specify the same region as some prior lock call
locked regions become entirely inaccessible to other processes
duplicate handles created with AH=45h or AH=46h inherit locks, but
  handles inherited by child processes (see AH=4Bh) do not
under DR DOS 3.41 and 5.0, if a process opens a file without the no-
  inherit flag and then starts a child, any locks set by the parent
  are ignored, and the child will only get an error if it tries to
  lock an area previously locked by the parent process.	 Under Novell
  DOS 7, this function is fully supported as in MS-DOS.

See also

AX=440Bh,AH=BCh,AH=BEh,INT 2F/AX=110Ah,INT 2F/AX=110Bh


2018/09/04 17:23 · prokushev · 0 Comments