The Mac operating system has evolved with a number of different versions from a decade, and some of them are Panther, Tiger, Leopard, Snow Leopard, Lion etc. It uses HFS, HFS+ file systems in order to arrange files on its hard drives.
It includes several useful features and has been designed using UNIX. Mac OS X is one of the most advanced OS introduced by Apple. Steps to Undelete Mac Files from External Hard Drive