Why Programs Fail is about bugs in computer programs, how to find them, how to reproduce them, and how to fix them in such a way that they do not occur anymore. This is the first comprehensive book on systematic debugging and covers a wide range of tools and techniques ranging from hands-on observation to fully automated diagnoses, and includes instructions for building automated debuggers. This discussion is built upon a solid theory of how failures occur, rather than relying on seat-of-the-pants techniques, which are of little help with large software systems or to those learning to p