In Mac OS X v10.4 Tiger, Apple introduced a new system startup program called launchd. The launchd daemon takes over many tasks from cron, xinetd, mach_init, and init, which are UNIX programs that traditionally have handled system initialization, called systems scripts, run startup items, and generally prepared the system for the user. And they still exist on Mac OS X Tiger, but launchd has superseded them in many instances. These venerable programs are widely used by system administrators, open source developers, managers of web services, even consumers who want to use cron to manage iCal scheduling, and they can still be called with launchd. The launchd daemon also provides a big performance boost to your system. At any given time, only those daemons that are actually used are launched