The basis of all of Apple's operating system, is Darwin. When Steve Jobs was ousted from Apple, he recognized the need for a more robust operating system. He developed the NeXT company, and they came up with the NeXTSTEP OS. Apple bought them out, and it became OPENSTEP, then Rhapsody, before being forked into Darwin. Darwin is at the core of all of the Apple operating systems to date. Normally, the current iOS will be based on the same version as the current OSX. For example, OS 10.5 and iOS 1 were based on Darwin 9.0. iOS 4 and OS 10.6 were based on Darwin 10.0. OS 10.7 (Lion) and iOS 5 are based on Darwin 11.0, but then things get interesting. Mountain Lion(10.8) is based on Darwin 12.0, but iOS 6 is based on Darwin 13.0. That means, for once, the mobile system will be operating under a more advanced version of Darwin than the desktop systems. Apple will not be replacing OS 10.8 for at least another year. It will be interesting to see how this plays out in the future. Will Apple continue to bring out a new iOS every year? When you think about the number of features each iOS has brought to us, it makes one salivate about the possibilities. I would not expect every release to be as feature full as iOS 6, but we are living in interesting times.