Daniel P. Bovet got a Ph.D. in computer science at UCLA in 1968 and is now full Professor at the University of Rome, "Tor Vergata," Italy. He had to wait over 25 years before being able to teach an operating system course in a proper manner because of the lack of source code for modern, well-designed systems. Now, thanks to cheap PCs and to Linux, Marco and Dan are able to cover all the facets of an operating system from booting to tuning and are able to hand out tough, satisfying homework to their students. (These young guys working at home on their PCs are really spoiled; they never had to fight with punched cards.) In fact, Dan was so fascinated by the accomplishments of Linus Torvalds and his followers that he spent the last few years trying to unravel some of Linux's mysteries. It seemed natural, after all that work, to write a book about what he found.