A Commentary on the Sixth Edition UNIX Operating System by John Lions (later reissued as Lions' Commentary on UNIX 6th Edition) is a highly influential 1976 publication containing analytical commentary on the source code of the 6th Edition Unix computer operating system "resident nucleus" (i.e., kernel) software, plus copy formatted and indexed by Lions, of said source code obtained from the authors at AT&T Bell Labs. It is also commonly referred to as the Lions Book.Itself an exemplar of the early success of UNIX as portable code for a publishing platform, Lions's work was typeset using UNIX tools, on systems running code ported at the University, similar to that which it documented, see page vi.It was commonly held to be the most copied book in computer science. Despite its age, Lions's book is still considered an excellent commentary on simple, high quality code. Lions's work was most recently reprinted in 1996 by Peer-To-Peer Communications, and has been circulated, recreated or reconstructed variously in a number of media by other parties, e.g. see webpage of Greg Lehey. Source: Wikipedia (en)