Mac OS X

Mac OS X is Apple's computer operating system. It was originally based on Unix, and so it has many similarities to Linux.

About
Mac OS X is the 10th version of Mac OS (X = Roman 10), Apple gives the subversions names of animals:
 * 10.0 - Cheetah
 * 10.1 - Puma
 * 10.2 - Jaguar
 * 10.3 - Panther
 * 10.4 - Tiger
 * 10.5 - Leopard
 * 10.6 - Snow Leopard
 * 10.7 - Lion