This book contains 201 top principles, rules of thumb, assumptions, proverbs of software development. Each principle has a short explanation and its reference on a single page, and they are organized by lifecycle phase (requirements, design, etc.). The purpose of the book is to enumerate the underlying principles of good software development, not teach specific techniques. The book is meant to be read by those new to software engineering so they can quickly grasp the principles that have evolved from more experienced people. It also provides who and where first stated a principle, which can be handy for researchers.