Where Mac OS X 10.4 Tiger had come in separate versions for PowerPC and Intel Macs, the Leopard installer could run on both platforms, and the version of Mac OS X installed could boot either type of hardware. Leopard itself was also a unified operating system. For the first time, a version of OS X was certified as Unix, and the new unified appearance makes Leopard friendlier and less confusing for users.
Mac OS X 10.5 Leopard, released on October 26, 2007, was the biggest change to Mac OS X since Apple first released OS X 10.0 in March 2001.
