BGE S1-S3 computing science and digital literacy : third and fourth levels

148 Pages·2021·10.431 MB·English

by  David Alford

A whole-school approach to BGE
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BGE S1–S3
Computing Science
& Digital Literacy
Third and
Fourth Levels
David Alford
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© David Alford 2021
First published in 2021 by
Hodder Gibson, an imprint of Hodder Education
An Hachette UK Company
211 St Vincent Street
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Year 2025 2024 2023 2022 2021
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A catalogue record for this title is available from the British Library.
ISBN: 978 1 3983 1321 7
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Contents
Introduction 1
1 Computer systems
1.1 Binary 2
1.2 CPU and main memory 4
1.3 Backing storage devices 6
1.4 Input and output devices 8
1.5 Networks 10
2 Staying safe online
2.1 Personal data and privacy 12
2.2 The Internet of Things 14
2.3 Hacking and DOS attacks 16
2.4 Malware and phishing 18
2.5 Protecting computer systems 20
2.6 Real-world examples of cybercrime 22
2.7 Searching the Web 24
3 Game creation
3.1 Introduction to Scratch 26
3.2 Events: avoid the enemy 30
3.3 Variables: catch the objects 34
3.4 Constructs: Racemania 36
3.5 Parallel processes: Bat in a cave 40
3.6 Parameters: the random number function 42
3.7 Practical challenges 44
4 Coding basics
4.1 Calculations in Scratch 46
4.2 Solving problems with fixed loops 48
4.3 Solving problems with conditional statements 50
4.4 Solving problems with conditional loops 52
4.5 Practical challenges 53
4.6 Practice questions 54
5 Text-based coding
5.1 Input and output in Python 56
5.2 Conditional statements in Python 59
5.3 Fixed loops in Python 62
5.4 Conditional loops in Python 64
5.5 The software development process 67
5.6 Design techniques 70
5.7 Practical challenges 72
5.8 Practice questions 74
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6 Web design
6.1 Introduction to web design 76
6.2 Designing a website 78
6.3 Basic structure of a web page 80
6.4 Hyperlinks and the anchor tag 82
6.5 Embedding media 84
6.6 CSS: styling other elements 87
6.7 CSS: styling text 90
6.8 JavaScript events 92
6.9 Practical challenges 94
6.10 Practice questions 96
7 Databases
7.1 What is a database? 98
7.2 Real-world case study 100
7.3 Designing a database 102
7.4 Creating a database in MS Access 104
7.5 Adding images 108
7.6 Validation 110
7.7 Database creation challenges 112
7.8 Searching a database 114
7.9 Sorting a database 115
7.10 Complex queries 116
7.11 Practical challenges 118
7.12 Practice questions 120
Glossary 122
Answers 125
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Introduction
The aim of this book is to help you enjoy developing your skills and understanding
as you experience the computing science and digital literacy concepts contained
in the technologies area of Curriculum for Excellence. This book will not only help
you excel at applying your computing science knowledge, but will also assist in
your progress in literacy, numeracy, career education and health and wellbeing
outcomes.
u How to use this book
This book is best used as part of a series of lessons on each topic led by your
teacher, who may use the Teacher’s Guide and resources available on the Hodder
Gibson website to support them.
The book is divided into chapters. Each chapter has one topic and contains many
sub-topics. The topics can be completed in any order as decided by your teacher,
apart from Chapters 3–5, where the coding skills required in later chapters build
on those skills learnt earlier.
Each sub-topic begins with an explanation of any new or key concepts. The ‘Work
it out’ section contains questions to which you can write your answers in a jotter
or type out the answers on a device. These answers should be found within the
earlier explanation in the chapter. It is always best to answer in sentences so
that the statements in your answers make sense when you revise them for any
assessments. The ‘Activities’ section contains tasks where you apply your skills
using software on a device.
If there are any computing science terms that are unfamiliar, you will find a
definition in the Glossary at the end of the book.
1
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1.1 Binary
Learning intentions Did you
know?
●  Understand that computers store data using 0s and 1s.
●  Understand how real-world information is changed into 0s and 1s. Digit is another 
word for finger.
u Number systems
Humans count using a number system with ten digits (0–9). This is probably
because we have ten fingers. The number system with ten digits is called
denary. However, computers store information using only two digits. This
number system is called binary.
Here are some of the reasons that computers use only two digits:
● Two possibilities can be easily stored.
● Two possibilities are less likely to experience errors when being sent to
other devices.
● There are fewer rules for calculations when there are only two digits.
›› Place values
In the numbers you are used to (denary), the place values start with one at the
right, and multiply by ten each time. So, 25 314 is:
Did you
×10 ×10 ×10 ×10
know?
Place value 10 000 1000 100 10 1
Digit 2 5 3 1 4 A binary digit, 
that is, a 0 or a 
In binary, the place values start with one at the right, and multiply by two each 1, is known as a 
time. So, the binary number 10110011 would be written as: bit: it’s made up 
from the words 
×2 ×2 ×2 ×2 ×2 ×2 ×2
‘binary’ and 
Place value 128 64 32 16 8 4 2 1 ‘digit’ squashed 
Digit 1 0 1 1 0 0 1 1 together!
You can work out what a binary number is in denary by adding up the place
values wherever there is a ‘1’ for that place value. The example above would be
128+32+16+2+1, which equals 179. So, 10110011 in binary is 179 in denary.
u Storing text
Any key you press on the keyboard has a unique code made up of 0s and 1s.
One common method of storing text as 0s and 1s is called extended ASCII.
Extended ASCII uses eight binary digits for each character. One letter, number or
punctuation symbol is called a character.
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Computer systems
u Storing images
›› Vector storage
Images that have been created on the computer can be stored as text using extended
ASCII. The text will contain the names of objects and each object’s attributes. For
example, the object might be a rectangle and might have attributes such as how
many pixels wide it is, how high it is, the coordinates on the screen where it begins,
the fill colour and the line colour. Here is an example in a language called SVG:
<rect x="300" y="5" width="200" height="120"
style="fill:yellow; stroke:blue"/>
›› Bitmap storage
Did you
know?
Captured images, such as photos, have to be stored using bitmap storage. Each possible
colour has been assigned a unique code, a combination of 1s and 0s, in the same way as
A pixel is a 
extended ASCII gives each character a unique code. Bitmap storage involves storing the
square that 
colour codes for each pixel, in order, like a ‘map’ of the image or screen. The resolution
makes up an 
is the number of pixels in the screen/image, usually given as width x height, for example
image. The word 
1024x768. A higher resolution means higher quality, but also a bigger file size. Bitmap
‘pixel’ is short for 
images are often compressed to reduce file size so that they take up less space on
picture element.
backing storage and take less time to transfer across a network.
Work it out
1  How many digits are there in denary? 9  What is extended ASCII used for?
2  What is the name for the number system  10  What is a character?
that uses only two digits?
11  What is the name given to the tiny squares 
3  Give two reasons that computers use 0s and  that make up images on the computer?
1s to represent data.
12  Which method of storage stores objects and 
4  Convert 00001011 from binary into denary. their attributes?
5  Convert 10010101 from binary into denary. 13  How are bitmap images stored?
6  Convert 11000011 from binary into denary. 14  What is the term for the number of pixels in 
an image?
7  Convert 01111100 from binary into denary.
15  Why are bitmap images often compressed?
8  Convert 10101000 from binary into denary.
Activities
Do some research on the World Wide Web to find  3  An SVG tutorial. See if you can find out how 
the following. Make a note of the websites you use. to make:
a)  a red rectangle
1  A binary game, so you can practise converting 
binary to denary. b)  a yellow ellipse
2  An extended ASCII table. Write out the binary  c)  a pink line
codes for the word ‘Computing’. d)  a combination of shapes that make a cool logo.
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1.2 CPU and main memory
u Main memory
Learning
intention
There are two kinds of main memory in a computer system: ROM and RAM.
● Understand 
how the CPU 
›› ROM
and main 
memory each 
ROM stands for Read Only Memory. This is because the contents of ROM
contribute to 
cannot easily be erased or changed. ROM keeps the data stored there even if
the operation 
the computer is switched off. ROM is used to store the instructions that tell the
of a computer 
computer how to start up the operating system when it is switched on. The
system.
operating system is the collection of key important programs that allow the
computer to function. Using the instructions in the ROM, the operating system is
loaded into the RAM when the computer starts up.
›› RAM
A computer program is a list of instructions.
This is true whether the program is a part of
the operating system, a game, a browser or
anything else. Programs that are currently
running and files/data that they are using
are stored in RAM while they are open. If
the computer has to open more programs
than there is room for in the RAM, it will run
more slowly because it uses backing storage
to hold them. This is called virtual memory.
RAM stands for Random Access Memory.
The contents of RAM can easily be erased –
and this is a good thing – it’s what allows
▲ Figure 1.1 RAM being inserted into a computer’s motherboard
us to run different programs on the same
computer. RAM loses the data stored there if the computer is switched off, which
is why if there is a power cut then you lose your unsaved work!
u The CPU
CPU stands for Central Processing Unit
and is often called the processor. The CPU
ensures that the instructions of the running
programs are carried out. To do this, it has
to be able to get the instructions from RAM
(or occasionally ROM) and send data to
RAM to be stored there. The collections of
lines that carry data between the CPU and
main memory are called buses. ▲ Figure 1.2 A CPU being installed on a computer’s motherboard
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