The design of this book is based on teaching the ]SP (Jackson Structured Pro gramming) methodology to undergaduates and postgraduates over a period of a number of years. I am grateful for the comments and feedback that have been provided by students who have taken these courses. The aim of the book is to provide readers with an understanding of the concepts behind the ]SP methodology in order that they may apply it for themselves; simply using the notation is not sufficient, it must be used appropriately. The answer to the question "Why is this wrong?" can lead to a greater understanding than...