Table Of ContentDynamic Learning is an online subscription solution that supports teachers and students with high
quality content and unique tools. Dynamic Learning incorporates elements that all work together to give
you the ultimate classroom and homework resource.
Teaching and Learning titles include interactive resources, lesson planning tools, self-marking tests
and assessment. Teachers can:
● Use the Lesson Builder to plan and deliver lessons
● Share lessons and resources with students and colleagues
● Track student’s progress
Teachers can also combine their own trusted resources alongside those from Cambridge International
AS & A Level Computer Science Online Teacher’s Guide which has a whole host of informative and
interactive resources including:
● Teaching notes and guidance
● Schemes of work
● Extra activities and exam-style questions
● Answers to questions in the Student’s Book
Cambridge International AS & A Level Computer Science is available as a Whiteboard
eTextbook which is an online interactive version of the printed textbook that enables teachers to:
● Display interactive pages to their class
● Add notes and highlight areas
● Add double-page spreads into lesson plans
Additionally the Student eTextbook of Cambridge International AS & A Level Computer Science
is a downloadable version of the printed textbook that teachers can assign to students so they can:
● Download and view on any device or browser
● Add, edit and synchronise notes across two devices
● Access their personal copy on the move
To find out more and sign up for free trials visit: www.hoddereducation.com/dynamiclearning
Cambridge
International AS & A Level
Computer
Science
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 1 4/30/19 7:42 AM
This page intentionally left blank
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 2 4/30/19 7:42 AM
Cambridge
International
AS & A Level
Computer
Science
David Watson
Helen Williams
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 3 4/30/19 7:42 AM
Unless otherwise acknowledged, the questions, example answers and comments that appear in this book were
written by the authors. In examinations, the way marks are awarded may be different. Questions from the
Cambridge International AS & A Level Computer Science papers are reproduced by permission of Cambridge
Assessment International Education. Cambridge Assessment International Education bears no responsibility for
the example answers to questions taken from its past question papers which are contained in this publication.
The publishers would like to thank the following who have given permission to reproduce the following material
in this book:
Page 181 Extract from IEEE Code of Ethics. Reprinted with permission of IEEE with the copyright notice © Copyright
2018 IEEE; Pages 181–3 Copyright © 1999 by the Institute for Electrical and Electronics Engineers, Inc. and the
Association for Computing Machinery, Inc.; Page 187 eBay software pirates stump up $100,000 – https://www.
theregister.co.uk/2006/11/24/ebay_pirates_payup/. Reprinted with permission of Out-Law.com, the news service of
international law firm Pinsent Masons; Page 218 Map data © 2018 Google, Imagery © 2018 Landsat/Copernicus.
Photo credits
Figures 1.1 and 1.2 © David Watson; Figure 1.3 © Sébastien Delaunay/stock.adobe.com; Figure 2.18 © Forgem/
Shutterstock.com; Figure 3.1 tl © studio306fotolia/stock.adobe.com; tr © Chavim/stock.adobe.com; bl © pozdeevvs/
stock.adobe.com; br © Sergey Yarochkin/stock.adobe.com; Figure 3.4 © Mau Horng/stock.adobe.com; Figure 3.5
© science photo/stock.adobe.com; Figure 3.9 © Maksym Dykha/Shutterstock.com; Figure 3.10 © Hurst Photo/
Shutterstock.com; Figure 3.11 © philipus/stock.adobe.com; Figure 3.12 © belekekin/ Shutterstock.com;
Figure 4.4 l © cybertrone/stock.adobe.com, c © Tungphoto/Shutterstock.com, r © Luminis/Shutterstock.com;
Figure 5.1 l © Stuart Brady (Public Domain) via Wikipedia Commons; r © Jiri Hera/stock.adobe.com; Figure 6.3
© Andrey Burmakin/stock.adobe.com; Figure 6.4 © bkilzer/stock.adobe.com; Figure 7.2 l © Pres Panayotov/
Shutterstock.com; c © James Balog/Getty Images; r © caluian/stock.adobe.com; Figure 18.19 © seewhatmitchsee/
123rf.com; Figure 18.21 b © Garmon/stock.adobe.com; t © Christian Musat/stock.adobe.com; ct © Ammit/stock.
adobe.com; cb © Martina Berg/stock.adobe.com; Figure 18.24 Harshal/stock.adobe.com; Figures 18.27 and 18.28
all © David Watson.
l = left, c = centre, b = bottom, t = top, r = right
Every effort has been made to trace and acknowledge ownership of copyright. The publishers will be glad to
make suitable arrangements with any copyright holders whom it has not been possible to contact. Computer
hardware and software brand names mentioned in this book are protected by their respective trademarks and
are acknowledged.
Although every effort has been made to ensure that website addresses are correct at time of going to press,
Hodder Education cannot be held responsible for the content of any website mentioned in this book.
Hachette UK’s policy is to use papers that are natural, renewable and recyclable products and made from wood
grown in well-managed forests and other controlled sources. The logging and manufacturing processes are
expected to conform to the environmental regulations of the country of origin.
Orders: please contact Bookpoint Ltd, 130 Park Drive, Milton Park, Abingdon, Oxon OX14 4SE. Telephone:
(44) 01235 827827. Fax: (44) 01235 400401. Email [email protected] Lines are open from
9 a.m. to 5 p.m., Monday to Saturday, with a 24-hour message answering service. You can also order through
our website: www.hoddereducation.com
© David Watson and Helen Williams 2019
First published 2019 by
Hodder Education,
An Hachette UK Company
Carmelite House
50 Victoria Embankment
London EC4Y 0DZ
www.hoddereducation.com
Impression number 10 9 8 7 6 5 4 3 2 1
Year 2023 2022 2021 2020 2019
All rights reserved. Apart from any use permitted under UK copyright law, no part of this publication may be
reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and
recording, or held within any information storage and retrieval system, without permission in writing from the
publisher or under licence from the Copyright Licensing Agency Limited. Further details of such licences (for
reprographic reproduction) may be obtained from the Copyright Licensing Agency Limited, www.cla.co.uk
Cover photo © Terrance Emerson – stock.adobe.com
Illustrations by Aptara Inc. and Hodder Education
Typeset by Aptara Inc.
Printed by Bell & Bain Ltd, Glasgow
A catalogue record for this title is available from the British Library.
ISBN: 9781510457591
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 4 4/30/19 7:42 AM
Contents
Introduction viii
AS LEVEL
1 Information representation and multimedia 1
1.1 Data representation 2
1.2 Multimedia 15
1.3 File compression 21
2 Communication 27
2.1 Networking 28
2.2 The internet 54
3 Hardware 68
3.1 Computers and their components 68
3.2 Logic gates and logic circuits 89
4 Processor fundamentals 107
4.1 Central processing unit (CPU) architecture 107
4.2 Assembly language 121
4.3 Bit manipulation 130
5 System software 136
5.1 Operating systems 136
5.2 Language translators 149
6 Security, privacy and data integrity 159
6.1 Data security 159
6.2 Data integrity 169
7 Ethics and ownership 178
7.1 Legal, moral, ethical and cultural implications 179
7.2 Copyright issues 186
7.3 Artificial intelligence (AI) 189
8 Databases 196
8.1 Database concepts 196
8.2 Database management systems (DBMSs) 208
8.3 Data definition language (DDL) and data manipulation
language (DML) 211
v
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 5 4/30/19 7:42 AM
s 9 Algorithm design and problem solving 217
t
n
e
t 9.1 Computational thinking skills 217
n
o 9.2 Algorithms 219
C
10 Data types and structures 238
10.1 Data types and records 238
10.2 Arrays 241
10.3 Files 249
10.4 Abstract data types (ADTs) 250
11 Programming 264
11.1 Programming basics 264
11.2 Programming constructs 271
11.3 Structured programming 275
12 Software development 283
12.1 Program development lifecycle 283
12.2 Program design 287
12.3 Program testing and maintenance 293
A LEVEL
13 Data representation 304
13.1 User-defined data types 304
13.2 File organisation and access 308
13.3 Floating-point numbers, representation and manipulation 312
14 Communication and internet technologies 328
14.1 Protocols 328
14.2 Circuit switching and packet switching 337
15 Hardware 346
15.1 Processors and parallel processing 346
15.2 Boolean algebra and logic circuits 354
16 System software and virtual machines 372
16.1 Purposes of an operating system (OS) 372
16.2 Virtual machines (VMs) 392
16.3 Translation software 394
vi
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 6 4/30/19 7:42 AM
17 Security 410 C
o
n
t
17.1 Encryption 410 e
n
17.2 Quantum cryptography 414 t
s
17.3 Protocols 416
17.4 Digital signatures and digital certificates 418
18 Artificial intelligence (AI) 425
18.1 Shortest path algorithms 425
18.2 Artificial intelligence, machine learning and deep learning 434
19 Computational thinking and problem solving 450
19.1 Algorithms 450
19.2 Recursion 490
20 Further programming 498
20.1 Programming paradigms 498
20.2 File processing and exception handling 525
Glossary 541
Index 553
vii
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 7 4/30/19 7:42 AM
n Introduction
o
I
t
C
U
D
o This textbook provides the knowledge, understanding and practical skills
R
t to support those studying Cambridge International AS & A Level Computer
n
I Science. This textbook is part of a suite of resources which include a
Programming Skills Workbook and an Online Teacher’s Guide.
The syllabus content has been covered comprehensively and is presented in two
sections: Chapters 1 to 12 cover the AS Level, Chapters 13 to 20 cover the extra
content required for the full A Level.
How to use this book
To make your study of Computer Science as rewarding and successful as possible,
this textbook, endorsed by Cambridge Assessment International Education, offers
the following important features.
Organisation
The content is presented in the same order as in the syllabus, and the chapter
titles match those in the syllabus.
Features to help you learn
Each chapter is broken down into several sections, so that the content is
accessible.
At the start of each chapter, there is a blue box that gives a summary of the
syllabus points to be covered in that chapter, to show you what you are going
to learn.
In this chapter, you will learn about
★ binary magnitudes, binary prefixes and ★ how to estimate the file size for a bit-map image
decimal prefixes ★ image resolution and colour depth
★ binary, denary and hexadecimal number ★ encoding of vector graphics
systems ★ the representation of sound in a computer
★ how to carry out binary addition and ★ the effects of changing sampling rate and
subtraction resolution on sound quality
★ the use of hexadecimal and binary coded ★ the need for file compression methods (such
decimal (BCD) number systems as lossy and lossless formats)
★ the representation of character sets (such as ★ how to compress common file formats
ASCII and Unicode) (such as text files, bit-map images, vector
★ how data for a bit-mapped image is encoded graphics, sound files and video files).
The grey-blue What you should already know boxes at the beginning of each
chapter or section help you to check you have the right level of knowledge
before you begin. You may have already studied Computer Science at IGCSE,
O Level or equivalent, or you may not have. These boxes contain questions to
find out how much you remember, or to gauge your previous learning. If you are
unable to answer the questions, you will need to refresh your memory, or make
sure you are familiar with the the relevant ideas, before continuing.
viii
457591_FM_CI_AS & A_Level_CS_i-xiv.indd 8 4/30/19 7:42 AM
