well as allowing load order to be altered without renaming items. Extensions were only loaded at startup time, meaning that any attempted change required a reboot. The most common time for extension conflicts to start was the release of a new version of the operating system, followed closely by the installation of a complex new application that either conflicted with existing extensions, or installed extensions that conflicted with the existing set. All of this was mitigated by the ease with which extensions and the operating system itself could be swapped in and out: Instead of modifying configuration files as on other operating systems, extensions and other automatically run software simply had to reside in a particular subfolder of the System Folder to be picked up. And load their order could be altered by renaming items in the Finder, based on descending ASCIIbetical order for each System subfolder. In addition, the Mac was perfectly happy to have two (or more) System Folders present on a hard drive. Only the "blessed" System Folder would be loaded at startup. So, when a new version of the operating system was to be installed, or a new application, the user could easily duplicate the system folder, perform the install, and then fall back if a problem resulted. Extension conflicts came to an end with the release of Mac OS X, which uses a different extension mechanism. Software can still add new features to the Mac but instead of requiring a kernel extension, the new method has allowed Apple to push more and more extensions into user space, which is a safer and more organized approach that cannot destabilize the entire machine. See also Configuration management Dependency management Dependency hell DLL hell JAR hell Portable application Portable application creators References Classic Mac OS