David Watson & Helen Williams 
Cambridge IGCSE and O Level Computer Science Study and Revision Guide Second Edition 

Stretch yourself to achieve the highest grades, with structured syllabus coverage, varied exam-style questions and annotated sample answers, to help you to build the essential skill set for exam success.- Benefit from expert advice and tips on skills and knowledge from experienced subject authors- Target revision and focus on important concepts and skills with key objectives at the beginning of every chapter- Keep track of your own progress with a handy revision planner- Consolidate and apply your understanding with exam-style questions- Apply your understanding of theoretical content and practical skills with sample practice papers, written by the authors, at the end of the book and online.Answers can be found at hoddereducation.com/cambridgeextras