DOS Fn 5c01H: Unlock File Access

                                                         Compatibility: 3.0+ 
 Expects: AX    5c01H
          BX    file handle
          CX:DX file offset from start of file    (CX * 65536)+DX
          SI:DI length in bytes of region to lock (SI * 65536)+DI
 Returns: AX    error code if CF is set to CY
    Info: This function unlocks access to a region of the file which was
          previously locked.

          See fn 5c00H for more details on file locking.

   Notes: ■ The offset and length must match exactly with the parameters
            used when the lock was applied.

          ■ It is important that all locks be removed from a file before a
            program is terminated.

          ■ It is recommended that you unlock as soon as possible.  Always
            try to lock, access the file, and unlock in one operation.

See Also: Network Functions
          Directory and File Functions
          DOS Functions