Software costs typically account for well over half of the total in computer systems, and this book discusses softwre and the importance of having a professional approach to softwre production. Professional practices are examined in the context of the planning and production of reliable robust softwre to meet a given specification. Leading from design techniques, through implementation practices into maintenance operations, this book aims to demonstrate economical and efficient ways in which software can be produced and kept up-to-date. Each of the book's four interdependant sections follows the life-cycle of the softwre product, with the notion of software engineering as the underlying and unifying principle.