The Design and Implementation of the 4.3BSD UNIX Operating System, by Samuel J. Leffler, Marshall Kirk McKusick, Michael J. Karels, and John S. Quarterman (Addison-Wesley Publishers, 1989, ISBN 0-201-06196-1); or The Design and Implementation of the 4.4 BSD Operating System by Marshall Kirk McKusick, Keith Bostic, Michael J. Karels and John S. Quarterman (Addison-Wesley Longman, 1996, ISBN 0-201-54979-4) Either of the standard reference books on the internals of BSD Unix. So called because the covers have a picture depicting a little demon (a visual play on daemon) in sneakers, holding a pitchfork (referring to one of the characteristic features of Unix, the fork(2) system call).