HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

               INT 21,5C - Lock/Unlock File Access  (DOS 3.0+)

       AH = 5C
       AL = 00  lock file
          = 01  unlock file
       BX = file handle
       CX = most significant word of region offset
       DX = least significant word of region offset
       SI = most significant word of region length
       DI = least significant word of region length


       on return:
       AX = error code if CF set  (see DOS ERROR CODES)


       - used for networking and multi-tasking system to preserve
         data integrity
       - duplicated handles inherit access to locked regions
       - EXEC'd programs do not inherit access to locked regions

Esc or Alt-X to exit int 21,5c Home/PgUp/PgDn/End ←↑↓→