INT 21 - ENVLOCK - INSTALLATION CHECK AX = 6262h SI = 1994h Return: AX = 1994h if installed ES = ENVLOCK's resident segment Notes: to deactivate ENVLOCK, zero out the byte at ES:[0102h] Program: ENVLOCK is a TSR(Terminate and Stay Resident) A program which remains in memory after terminating in order to provide services to other programs or the user. The name comes from the name of the DOS function call used to remain in memory after termination. by Alexander Yanovsky that forces other TSRs to deallocate their environment when they stay resident