All modern computers have some form of operating system which users generally
take for granted. The operating system makes it possible to communicate with the
software and hardware that make up a typical computer system.
This textbook has been written to provide the knowledge, understanding and practical skills that a student would need for the Cambridge International Examinations Computer Science IGCSE and GCE O Level courses.
As you progress through this book you will begin to realise how complex computer
systems really are. By the time you reach Chapter 12 you should have a better
understanding of the fundamentals behind computers themselves and the software that
The HEXADECIMAL SYSTEM is very closely related to the binary system. Hexadecimal
(sometimes referred to as simply "hex") is a base 16 system and therefore needs to
use 16 different "values" to represent each digit.