A new edition of a book entitled iOS Forensic Analysis by Sean Morrissey reveals the secret code names of the various versions of iOS, including the as-yet-unreleased iOS 5.1. Unlike the code names of OS X, which have been generally made public since v10.2, iOS code names have been kept unpublicized and are generally used only by Apple. The code names, most of which appeared in the original edition published a year ago, seem to be based on a theme of skiing areas.
