Prime Computer Science is a series of books written to help learners acquire basic concepts and skills that will provide the necessary impetus and aptitude to fit into a contemporary world of Information Technology and enable them to become critical, effective and independent users of ICT. They should also be able to benefit from the opportunities and advantages that ICT can provide to support learning in other areas of the curriculum. The authors have used the competence-based approach, which suggests specific tasks that the learners are expected to follow in order to meet the needs of a competitive and emergent information-driven economy.