History of Mac OS

Mac OS 9

Mac OS 9 was released on October 23, 1999. It was generally a steady evolution from Mac OS 8. Early development releases of Mac OS 9 were numbered 8.7. Mac OS 9 added improved support for AirPort wireless networking. It introduced an early implementation of multi-user support. Though not a true multi-user operating system, Mac OS 9 did allow multiple desktop users to have their own data and system settings. An improved Sherlock search engine added several new search plug-ins. Mac OS 9 also provided a much improved memory implementation and management. AppleScript was improved to allow TCP/IP and networking control. Mac OS 9 also made the first use of the centralized Apple Software Update to find and install OS and hardware updates. Other new features included its on-the-fly file encryption software with code signing and Keychain technologies, Remote Networking and File Server packages and much improved list of USB drivers.

Mac OS 9 also added some transitional technologies to help application developers adopt some OS X features before the introduction of the new OS to the public, again easing the transition. These included new APIs for the file system, and the bundling of the Carbon library that apps could link against instead of the traditional API libraries — apps that were adapted to do this can be run natively on OS X as well. Other changes were made in Mac OS 9 to allow it to be booted in the "Classic Environment" within OS X. This is a compatibility layer in OS X versions prior to 10.5 (in fact an OS X application, originally codenamed the "blue box") that runs a complete Mac OS 9 operating system, allowing applications that have not been ported to Carbon to run on OS X. This is reasonably seamless, though "classic" applications retain their original Mac OS 8/9 appearance and do not gain the OS X "Aqua" appearance.