DOS Fn 5cH: Lock/Unlock File Access

                                                         Compatibility: 3.0+ 
     See: Fn 5c00H (lock a region of a file)

          Fn 5c01H (unlock a region of a file)

    Note: Both functions use the same parameters.  The exact same offset
          and length must be used when unlocking as were used when locking.

See Also: Network Functions
          Directory and File Functions
          DOS Functions