This second edition of the AS Computer Science textbook is written in the straightforward, easy-to-grasp style for which Pat Heathcote and Rob Heathcote are well-known. Each chapter in the book corresponds to roughly one lesson, and contains questions and exercises which can be done in class, as well as questions at the end of each chapter which can be set as homework. Answers to all questions are provided in downloadable pdf format available free to teachers from the PG Online website. This book is divided into six sections comprising 36 chapters, which together provide complete coverage of the new AS course and the first year of the full A Level course. The specification is written in such a way that AS and A Level students can be taught together. Programming solutions within the textbook are all written in pseudocode to suit all practical languages being taught alongside the theory. To accompany this textbook, PG Online also publishes a series of six downloadable teaching units. Each topic in a unit consists of a PowerPoint presentation, teacher's notes, worksheets, homework sheets and a final assessment test with exam-style questions.Pat Heathcote and Rob Heathcote both have years of experience as teachers, authors and examiners.