Mac OS X Leopard

Mac OS X Leopard, or Mac OS X 10.5, is the sixth major release of Mac OS X that was released on 26 October 2007. Leopard was supposed to be released in 2006, but it was delayed due to the launch of the iPhone. It is the first version of Mac OS X to drop support for G3 systems and introduces a new version of Aqua that Apple would use until Snow Leopard. It is also the last version of Mac OS X to have support for Intel Pentium 4 processors, though this can only be seen with Hackintoshes as no retail Macs shipped with Pentium 4s. The Universal Binary concept was extended in Leopard, as the separate builds for Intel and PowerPC Macs were unified in Leopard and installation media could be used for either system. The first 64-bit Mac applications were designed for Leopard due to a new 64-bit userland (the kernel remained 32-bit until Snow Leopard).

New features and changes

 * Updated the UI with a 3D reflective Dock, transparent menu-bar, and unified iTunes-like window chrome.
 * Stacks for providing shortcuts to files on the Dock.
 * Spaces, a multi-workspace manager.
 * Time Machine, a backup utility.
 * Safari 3 with support for WebClips.
 * Support for RSS feeds, Stationery, Notes, and to-dos in Mail.
 * Boot Camp, a software assistant used for dual booting Windows.
 * Front Row now resembles the interface of the original Apple TV.
 * Updated Finder with a new sidebar, Cover Flow, and multithread support.
 * Quick Look, which allows previewing files in Finder without launching an app.
 * Core Animation, an API allowing for keyframe animation in the OS X UI.
 * 64-bit applications, userland, and system libraries.
 * Removed support for Classic applications.