1st Edition January 1999 1-56592-582-3, Order Number: 5823 280 pages, $24.95 Twenty Years of Berkeley Unix From AT&T-Owned to Freely Redistributable Marshall Kirk McKusick Early History Ken Thompson and Dennis Ritchie presented the first Unix paper at the Symposium on Operating Systems Principles at Purdue University in November 1973. Professor Bob Fabry, of the University of California at Berkele