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, Cambridge
IGCSE™ and O level
Computer
Science
Second Edition
David Watson
Helen Williams
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,Contents
Introduction v
SECTION 1 COMPUTER SYSTEMS 1
1 Data representation 2
1.1 Number systems 2
1.2 Text, sound and images 25
1.3 Data storage and file compression 32
2 Data transmission 45
2.1 Types and methods of data transmission 45
2.2 Methods of error detection 54
2.3 Symmetric and asymmetric encryption 63
3 Hardware 75
3.1 Computer architecture 75
3.2 Input and output devices 88
3.3 Data storage 119
3.4 Network hardware 133
4 Software 147
4.1 Types of software and interrupts 147
4.2 Types of programming language, translators and
integrated development environments (IDEs) 165
5 The internet and its uses 180
5.1 The internet and the World Wide Web (WWW) 180
5.2 Digital currency 186
5.3 Cyber security 189
6 Automated and emerging technologies 217
6.1 Automated systems 217
6.2 Robotics 230
6.3 Artificial intelligence (AI) 241
iii
, SECTION 2 ALGORITHMS, PROGRAMMING
AND LOGIC 257
7 Algorithm design and problem solving 258
7.1 The program development life cycle 258
7.2 Computer systems, sub-systems and decomposition 260
7.3 Explaining the purpose of an algorithm 271
7.4 Standard methods of solution 272
7.5 Validation and verification 276
7.6 Test data 281
7.7 Trace tables to document dry runs of algorithms 282
7.8 Identifying errors in algorithms 285
7.9 Writing and amending algorithms 288
8 Programming 299
8.1 Programming concepts 302
8.2 Arrays 329
8.3 File handling 333
9 Databases 339
9.1 Databases 339
10 Boolean logic 356
10.1 Standard logic gate symbols 356
10.2 The function of the six logic gates 358
10.3 Logic circuits, logic expressions, truth tables and
problem statements 360
Index 387
iv
, Introduction
Introduction
Aims
This book has been written for students of Cambridge IGCSETM Computer Science
(0478/0984) and Cambridge O Level Computer Science (2210) for examination
from 2023. It fully covers the syllabus content, provides guidance to support you
throughout the course and helps you to prepare for examination.
This book will help students to develop a range of skills, including programming,
problem solving and testing and evaluation, as well as introducing them to
automated and emerging technologies.
Assessment
The information in this section is taken from the Cambridge IGCSE and O Level
Computer Science syllabuses (0478/0984/2210) for examination from 2023. You
should always refer to the appropriate syllabus document for the year of examination
to confirm the details and for more information. The syllabus document is available
on the Cambridge International website at: www.cambridgeinternational.org
There are two examination papers:
Paper 1 Computer Systems Paper 2 Algorithms,
Programming and Logic
Duration 1 hour 45 minutes 1 hours 45 minutes
Marks 75 marks 75 marks
Percentage of overall marks 50% 50%
Syllabus topics examined 1–6 7–10
How to use this book
The information in this section is taken from the Cambridge IGCSE and O Level
Computer Science syllabuses (0478/0984/2210) for examination from 2023. You should
always refer to the appropriate syllabus document for the year of your examination to
confirm the details and for more information. The syllabus document is available on
the Cambridge International website at www.cambridgeinternational.org
Organisation
The content is organised into 10 chapters, corresponding to the syllabus. The
content is in the same order as the syllabus. The material directly relevant
to Computer Systems is in Chapters 1–6 and the material directly relevant to
Algorithms, Programming and Logic is in Chapters 7–10.
v
,INTRODUCTION
Features
Learning outline
Each chapter opens with an outline of the subject material to be covered.
In this chapter, you will learn about:
★ automated systems
– the use of sensors, microprocessors and actuators in automated systems
– the advantages and disadvantages of using automated systems in given
scenarios
★ robotics
– what is meant by robotics
– the characteristics of a robot
– the roles, advantages and disadvantages of robots
★ artificial intelligence
– what is meant by artificial intelligence (AI)
– the main characteristics of AI
– the basic operation and components of AI systems to simulate intelligent
behaviour.
Chapter introduction
A short introduction to the chapter topics and their focus.
This chapter considers the hardware found in many computer systems.
The hardware that makes up the computer itself and the various input and
output devices will all be covered.
Activity
Short questions and exercises to help recap and confirm knowledge and
understanding of the concepts covered.
Activity 1.2
Convert the following denary numbers into binary (using both methods):
a 41 d 100 g 144 j 255 m 4095
b 67 e 111 h 189 k 33000 n 16400
c 86 f 127 i 200 l 889 o 62307
Example
Worked examples of technical or mathematical techniques.
Example 2
A camera detector has an array of 2048 by 2048 pixels and uses a colour depth of 16.
Find the size of an image taken by this camera in MiB.
1 Multiply number of pixels in vertical and horizontal directions to find total number
of pixels = (2 048 × 2 048) = 4 194 304 pixels
2 Now multiply number of pixels by colour depth = 4 194 304 × 16 = 67 108 864 bits
3 Now divide number of bits by 8 to find the number of bytes in the file =
(67 108 864)/8 = 8 388 608 bytes
4 Now divide by 1024 × 1024 to convert to MiB = (8 388 608)/(1 048 576) = 8 MiB.
vi
, Introduction
Find out more
Short activities that go a little beyond the syllabus, for those students who have
a deeper interest in the subject.
Find out more
Find out how buffers are used to stream movies from the internet to a device (such as
a tablet).
Advice
As well as library
Advice
routines, typical IDEs These provide tips and background, and also highlight any content that is not
also contain an editor, specifically covered in the syllabus.
for entering code, and
an interpreter and/or Links
a compiler, to run the Numerous topics in Computer Science are connected together. The Links feature
code. states where relevant material is covered elsewhere in the book.
Link Extension
For more details on Written for students interested in further study, and placed at the end of each
RAM, see Section 3.3. chapter, this optional feature contains details of more sophisticated topics that
are explored in the International A Level syllabus.
Extension
For those students considering the study of this subject The following diagram shows an artificial neural
at A Level, the following section gives some insight into network (with two hidden layers) – each circle, called
further study on a sub-set of machine learning called a unit or node, is like an ‘artificial neuron’:
deep learning.
A1 B1
Deep learning
Deep learning structures algorithms in layers (input 1
A2 B2
layer, output layer and hidden layer(s)) to create an
artificial neural network made up of ‘units’ or ‘nodes’,
which is essentially based on the human brain (i.e. its 2 A3 B3 1
interconnections between neurons). Neural network
systems are able to process more like a human and A4 B4
their performance improves when trained with more 3
and more data. The hidden layers are where data from A5 B5
the input layer is processed into something that can be
sent to the output layer. Artificial neural networks are
excellent at tasks that computers normally find hard. Neural networks are effective at complex visual
For example, they can be used in face recognition: processing such as recognising birds, for example,
by their shape and colour. There are many different
sizes, colours and types of bird, and machine learning
algorithms struggle to successfully recognise such a
wide variety of complex objects. But the hidden layers
in an artificial neural network allow a deep learning
algorithm to do so.
vii
, INTRODUCTION
Summary
At the end of each chapter there is a list of the main points from the chapter
that you should have a good understanding of.
In this chapter, you have learnt about:
✔ use of sensors, microprocessors and actuators in automated systems
✔ the advantages and disadvantages of automated systems in a number of key
areas
✔ what is meant by robotics
✔ what characterises a robot
✔ the role of robots in a number of areas
✔ the advantages and disadvantages of robots in a number of areas
✔ the concept of artificial learning (AI)
✔ the main characteristics of AI
✔ expert systems
✔ machine learning.
Key terms
Key terms are in red throughout the book and are defined at the end of each
chapter.
Key terms used throughout this chapter
bit – the basic computing element that is either 0 or 1, and is formed from the words Binary
digit
binary number system – a number system based on 2, in which only the digits 0 and 1 are
used
hexadecimal number system – a number system based on the value 16 which uses denary
digits 0 to 9 and letters A to F
error codes – error messages (in hexadecimal) generated by the computer
MAC address – MAC address - standing for Media Access Control, this address uniquely
identifies a device on the internet; it takes the form: NN-NN-NN-DD-DD-DD, where NN-
NN-NN is the manufacturer code and DD-DD-DD is the device code
IP address – IP address short for internet protocol address and identified as either IPv4
or IPv6; the IP address gives a unique address to each device connected to the internet,
identifying its location
hypertext mark-up language (HTML) – the language used to design, display and format
web pages
viii
