Special thanks to Henning Gutmann for sticking by this book. Special thanks to Aaron Oas for suggesting the idea to Tracy in the first place. Thanks to Laurie Petrycki, Jeffrey Holcomb, and all the others at O'Reilly & Associates. Thanks to Tim O'Reilly for backing this book. Thanks to all the first-draft reviewers: Bruce Perens, Eric Raymond, Eric Allman, Jon Orwant, Julie and Gerald Jay Sussman, Hal Abelson, and Guy Steele. I hope you enjoy this typo-free version. Thanks to Alice Lippman for the interviews, cookies, and photographs. Thanks to my family, Steve, Jane, Tish, and Dave. And finally, last but not least: thanks to Richard Stallman for having the guts and endurance to "show us the code."