Cambridge
Lower Secondary
Computing
8
Ben Barnes
Margaret Debbadi
Pam Jones
Tristan Kirkpatrick
SERIES EDITOR:
Lorne Pearcey
SAMPLE MATERIAL
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Contents
Introduction
8.1
Computer systems: The inside track
8.2
Networks and communication: Across the world in an instant
8.3
Making choices: Search and select
8.4
Testing conditions: Developing games
8.5
Click and collect: Data collection and validation
8.6
Software development: Testing
Glossary
Index
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Unit
8.4
Testing conditions:
Developing games
Get started!
Have you ever played a game where you had to make choices?
Discuss the following with a partner:
l What sort of decisions did you make in the last game
you played?
l Did you notice that the game progresses differently,
depending on which choices you made?
l Have you every played a game that contained bugs?
Computer programs need to be able to check user choices
and other conditions. They also need to be tested to make
sure that the program runs correctly for everyone.
In this unit, you will use Python to develop and test computer games that run different
sections of code, depending on the user’s input.
Learning outcomes
In this unit, you will learn to:
l create and follow a flowchart that uses conditional statements
l develop programs in Python that use conditional statements
l understand how AND, OR and NOT can be used in algorithms
l develop programs in Python that use AND, OR and NOT
l develop programs in Python using different data types
l develop programs using an iterative process
l develop and apply a test plan
l understand the need for using a range of test data
l test a program using suitable test data.
Warm up
In pairs, think about your journey to school this morning. What conditions did you or your
parents have to check before leaving home? For example:
l Have you eaten any food?
l Have you brushed your teeth?
l Is your schoolbag packed?
l Are the doors locked?
Make a list of all the conditions you can both think of.
Most computer programs also check conditions as they are running. The conditions depend
on what the program does. In this unit, you will see how a game, written in Python, checks
conditions to allow a player to move through it. You will also see how important it is to test the
game, so that it works correctly for every possible choice.
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Unit 8.4 Testing conditions: Developing games
SCENARIO
Younger children need to understand the importance
of secure passwords. Your school wishes to promote
online safety and, as a programmer, you have been
asked to create a text adventure game for young
children aged 8–10 years old. The game should
provide the children with some different pathways to
follow as they progress through a story.
The child will play the main character in the game.
They need to find the Chocolate Room in a sweet
shop. They will meet a robot and the sweet-shop
owner on their journey.
When they find and enter the Chocolate Room,
there will be two questions. If the child answers the
questions correctly, they will be given three letters
from a four-letter password. They then have to guess
the password, after being given a clue. If they guess
the password correctly, they open a digital treasure chest and win the game.
Your challenge is to examine existing program code and find out what it does, correct errors in
the code and complete the game.
You need to use the different sample code provided by your teacher.
You will add new code, edit code and test any changes made to the code to make sure that it
works correctly.
DID YOU KNOW?
KEYWORDS
The first adventure games for computers were text adventure games. This was because
the computers were not powerful enough to display good graphics. A famous example
is the game Zork, which you can still play online today. Search for one of the early
Zork games online to find out the quality of the graphics computers of that time
could display.
text adventure game:
a game in which
the player types in
commands to control
the main character
program code: the
Python code created
in the IDLE
arithmetic operators:
+, – , *, / and other
symbols that can be
used for arithmetic
Do you remember?
Before starting this unit, you should be able to:
create an algorithm using flowchart symbols
understand the logic of AND, OR and NOT
understand the difference between integer, real and string
data types
know how to develop programs in Python with inputs
and outputs
use variables in Python
use arithmetic operators in Python
to debug a program.
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Cambridge Lower Secondary Computing
Conditional statements
Learn
Sometimes decisions have to be made in a program. This is usually because the program
has reached a point where there is more than one option or choice. For example: In the
adventure game, players must enter their name and age, and then (if over 8 years-old),
they will enter a name for the sweet-shop owner. After this, there are a number of
possible pathways for the program to follow, depending on how the player answers
certain questions.
Selection allow a program to check whether certain conditions have been met. This allows
the program to select different outcomes. Selection is important in programming,
because the programmer can offer the user choices about the way in which they move
through the program. Selection is achieved by using IF statements.
The structure of an IF statement
Here are two simple IF statements:
if playerage>10:
Condition 1 is that playerage is greater than 10.
print(“You are too old to play this game”)
if playerage<8:
Condition 2 is that playerage is less than 8.
print(“You are too young to play this game”)
This statement uses two conditions and two IF statements.
Remember logical operators:
Equal to
=
Not equal to
!=
Less than
<
Greater than
>
Less than or equal to
<=
Greater than or equal to
>=
Remember: A condition
contains a logical operator.
The logical operator combines
the parts of a condition
together. For example:
playerage>10 is a
condition. The condition
can evaluate to
true or false.
IF statements can be extended to IF—ELSE statements, which allow for more than one
outcome.
When a condition in an
IF statement evaluates
to true, the indented
statements following IF
are executed (but the
statements following
ELSE are not executed).
When a condition in an
IF statement evaluates
to false, the indented
statements following
ELSE are executed (but
the statements following
IF are not executed).
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Unit 8.4 Testing conditions: Developing games
KEYWORDS
For example, this IF—ELSE statement allows for two
different outcomes:
if (playerage>=8:
print(“You can play this game”)
else:
print(“You cannot play this game”)
Here is a flowchart representing the solution. You can see the two
possible paths:
1 one for ‘Yes’, when the condition is true and the statements
following IF are carried out
selection: selecting
statements based on
a decision
condition: an
expression that
evaluates to true or
false; for example,
is age <10?
indentation: move
the Python code four
spaces to the right
2 one for ‘No’, when the condition is false and the statements
following ELSE are carried out.
Playerage >= 8
Yes
Print ‘You can
play this game’
No
Continue with
the rest of the
program
Print ‘You cannot
play this game’
End program
The exact way of writing IF—ELSE statements in
Python is as follows:
if condition:
#statements to be
#carried out when the
#condition is true
else:
#statements to be
#carried out when the
#condition is false
Note the indentation used in the
lines following if and else. Python uses indentation
so that it knows which statements belong with if and which
belong with else.
You must include both the colons in an IF–ELSE statement in
Python. Python will indent the statements automatically
after you type the ‘:’ symbol.
If the indentation is not correct, you will get an error, because
Python needs to know which statements to group together.
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Cambridge Lower Secondary Computing
Practise
l
Open the file indentfile.py provided by your teacher.
l
The file has errors because the indentation of the print statements is incorrect.
Select the print statements as shown.
l
l
l
l
Use the dedent option to bring the print statements back to the correct position.
Save the program.
Run the program.
In a text adventure set in space,
the main character is an astronaut
exploring the caves of Mars. The player
notices a door on the right of the
main cave. The game asks the player
whether or not they wish to go through
the door.
Draw a flowchart to show how the
game can give the player the option
to either open the door or carry on
walking through the main cave.
DID YOU KNOW?
KEYWORD
You can use the indent function on Python’s menu
to highlight code and indent it all together.
dedent: move the
Python code out by
four spaces
If you want to remove the indent, you can highlight
the code and use the dedent feature. This will move
all highlighted code out by four spaces.
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Unit 8.4 Testing conditions: Developing games
Combining conditions using AND and OR
Learn
Decisions sometimes need to be made based on two or more conditions.
These conditions can be combined in different ways.
Remember:
AND and OR are called Boolean operators.
OR needs only one of the conditions to be
true to execute the statement that follows.
AND needs all of the conditions to be true
to execute the statement that follows.
Condition 1 OR Condition 2
Condition 1 AND Condition 2
Example 1: if you help the robot in the
adventure game with directions to the
Digital Sweet Shop OR help him with his
calculations, then you can have some sweets.
Example 2: if you help Botty with
directions to the Digital Sweet Shop
AND help him with his calculations,
then you can have some sweets.
What is the difference between the way in which conditions are combined in Example 1
and Example 2?
l
In Example 1, you only need to do one of the two tasks to receive the sweets.
l
In Example 2, you must do both tasks to receive the sweets.
IF statements in program code can be combined using logical operators such as AND
and OR.
Look at the following IF statement in Python. It is more efficient than the previous
examples, as two conditions have been combined into one.
if (playerage>=8 and playerage<=10):
print(“You can play this game”)
This IF statement is made up of two conditions.
The print statement is carried out only when both
condition 1 (playerage>=8) AND condition 2
(playerage<=10) are true.
Using the AND operator will give an overall outcome of true if both condition 1 and
condition 2 are true; otherwise it gives an overall outcome of false.
Here is another version of an IF statement that uses two conditions combined with the OR
operator.
Using the OR operator will give an outcome of true if either condition 1 or condition 2 is
true; otherwise it gives an overall outcome of false.
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Cambridge Lower Secondary Computing
This table shows when the print statement will be executed by the program when the user
inputs a few different ages.
Player age entered
Print statement executed
10
7
You are not the correct age to play this game! Sorry!!
9
20
You are not the correct age to play this game! Sorry!!
6
You are not the correct age to play this game! Sorry!!
12
You are not the correct age to play this game! Sorry!!
Multiple conditions can also be used within IF—ELSE statements.
For example, this IF—ELSE statement allows for two different outcomes:
if (playerage>=8 and playerage<=10):
print(“You can play this game”)
else:
print(“You cannot play this game”)
IF condition 3:
statements to be carried out when both conditions 1 and 2
are true.
ELSE:
statements to be carried out when either condition 1 or
condition 2 are false.
This means that if condition 1 is true but condition 2 is false,
the ELSE statement is executed.
Similarly, if condition 2 is true but condition 1 is false, the ELSE
statement is executed.
If condition 1 is false and condition 2 is false, then the ELSE
statement is executed.
Practise
l
Look at these IF statements relating to the playerage:
if playerage>10 or playerage <6:
print(“You can play the game”)
else:
print(“You cannot play the game”)
l
Using the IF statements above, copy and
complete the table by writing which print
statement will be executed for each of the
player ages entered. The first one has been
completed for you.
Player age entered
Print statement executed
10
You cannot play the game
7
9
20
6
4
l
Discuss with a friend how this IF statement will change the age rules for playing
the game.
l
Create a new IF statement, which will ensure that players aged 7 to 11 can play the
game. Use the following partially completed IF statement to help you.
if playerage >=7 and _________________________:
print _________________________
else:
print _________________________
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Unit 8.4 Testing conditions: Developing games
Computational thinking
Look at the code below on the left. Discuss with a partner what the output would be if you
enter the following values: x=4, y=7; x=8, y=8; x=11, y=21.
Look at the code below on the right. Which message will be output if you enter the
following values:
x=5, y=4, z=11
x=7, y=7, z=99
x=12, y=21, z=0
Create a set of values for x, y and z so that the message ‘Hello world’ is output.
Go further
Once the player has answered the robot’s question, they enter the Chocolate Room, where
they find the sweet-shop owner. She will ask the player a question, as follows:
Which of the following could be used as a good password?
1. Your pet’s name
2. Password123
3. A random set of numbers and letters.
The correct answer is 3. If the player enters 3, they can then pick one of two chocolate
bars by entering a number 1 or 2.
l If the player picks chocolate bar 1, there is no information in it and they lose a life.
l If the player picks chocolate bar 2, the letter ‘T’ is inside the wrapper.
If the player gives the wrong answer (1 or 2) to the owner’s password question, they lose
all their chocolate and lose a life.
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Cambridge Lower Secondary Computing
Some of the code for the Chocolate Room has been completed for you.
Look at the code with a partner.
Your challenge is to add the lines of code that are missing for
the Chocolate Room.
You can do this by opening the file ad62.py provided by your teacher and add the
required lines of code.
Ending the game
Once the player has left the Chocolate Room, the program will:
l ask the player to try to remember any of the letters they were given in the game
l ask the player to try to guess the password using the clue and the letters they
already know
l calculate and show the player their score.
l Add the lines of code that are missing from this section of the program. You can do
this by editing ad63.py provided by your teacher.
l Run the program and correct any errors.
l
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Unit 8.4 Testing conditions: Developing games
Challenge yourself!
Your challenge is to write a new text adventure game. The game is set in a series of tunnels
and the object of the game is for the player to find a key in one of the tunnels and then to
find their way to the exit. The exit is blocked by a gate that is unlocked by the key.
The game has the following features:
The player always walks forwards through the tunnels — they can’t go backwards.
l The first tunnel ends at a junction. At the first junction, the player can either take the
left tunnel, the middle tunnel or the right tunnel.
l Each of those tunnels also ends in a junction where the player can go left, middle or
right. This means that there are up to nine possible destinations in the game. Only one
of those destinations is the exit with the gate.
l One of the tunnels contains the key for the exit. You must design the game so that the
player can reach the exit from the tunnel that has the key — otherwise the game can
never be won!
l The junction containing the final exit must test whether the player has selected the
correct direction and if they have the key in order for them to win the game.
l Some of the other tunnels can have a range of different features, such as human
characters, monsters, dead-ends or hazards. You can design these features as you
wish — be imaginative!
l The player must pick up points every time they move through a tunnel, but they can
also lose points — for example, if they set off a trap. The game should update their
score using a variable and give them their score at the end.
l
The game should ask for the player’s name at the start of the program and then address
them by their name throughout the game. If the player does not enter a name, then the
code containing the rest of the game should not execute.
You should design your game using a flowchart algorithm before writing any code. Once
you have written your program, you should write a test plan and then test the game using
suitable test data.
13
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Cambridge Lower Secondary Computing
Final project
The skills you have learned in this unit were all in the context of a text adventure game.
However, these skills can be used in any kind of program that you write. In this project,
you will use your skills to develop and test a quiz game.
You are now going to create a new game for use with 10 to 11 year-olds to test their
mental arithmetic. Players will be asked to enter two numbers to multiply together, and
then asked to give the answer. The program will tell them if they are right or wrong. You
will use all the skills you’ve learned in this unit to create the game using Python.
Before you write any code, create a flowchart algorithm based on the details listed
below. When you are sure that your flowchart fully covers all the requirements of the
game, write the code for the game in Python.
Your game should have the following features:
l An introductory screen with information about the game
l A section of code to allow the player to input their name and age, which must be
between 10 and 11, as older or younger players are not allowed to play
l A section of code to print a welcome message and the player’s details on the screen
l A section of code that asks the player which two numbers they wish to multiply
together, and which then stores the first number in a variable called number1 and the
second number in a variable called number2, as real numbers
l A section of code that prints out number1 * number2 as an equation, with a question
mark, for example: What is 5 * 5?
l A section of code to calculate the result of multiplying the variable number1 by
number2, using use an assignment to store the result of this calculation in a variable
called result
l A section of code to allow the user to input their answer to the question, stored in a
variable called answer, and ensuring that the user’s input is stored as an integer
l A section of code, containing an IF statement, which checks to see if the answer equals
the result; if the result and the answer are the same, the player’s score increases by 10,
and the following message displays: ‘Correct — well done! You get 10 points!’
l A section of code that checks to see if the answer is within 1 of the result; if so, then
the player’s score increases by 1, and this message displays: ‘Incorrect — but you
were close! Have 1 point for trying and better luck next time.’
For example: If the result was 20, then an answer of 19 or 21 would display
this message.
A section of code that displays the following message for all other incorrect
answers: ‘Incorrect — you have scored 0 points.’
l A section of code to output the player’s score and a message stating that the
program has ended.
Run your game and correct any errors.
l
Once you have run your program, you need to test it.
l Create a test plan for your program.
l Select a range of test data and, for each case, explain why you chose it.
l Test your program using this test data. Record any further errors you discover before
correcting your program.
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Unit 8.4 Testing conditions: Developing games
Evaluation
l
Swap programs with a partner and play each other’s game. Comment on the following:
Does it cover all of the requirements?
l Is the game easy to use?
l Are the messages easy to understand?
l Are the scores correct for a range of different multiplications? (You should check
the calculations and keep a written record of each answer to see if the code is
working correctly.)
Now open your own program and look at the code. Reflect on what could be
improved in your game. Things you might want to think about include the following:
l What are the largest numbers that you’d expect 10 to 11 year-olds to be able to
multiply in their head?
l How easy would it be to change the program so that it could test addition and
subtraction?
Based on the evaluations, make a list of recommendations to improve your game.
l
l
l
What can you do?
Read and review what you can do.
I can create and follow a flowchart that uses conditional statements.
I can develop programs in Python that use conditional statements.
I can understand how AND, OR and NOT can be used within algorithms.
I can develop programs in Python that use AND, OR and NOT.
I can develop programs in Python using different data types.
I can develop programs using an iterative process.
I can develop and apply a test plan.
I can understand the need for using a range of test data.
I can test a program using suitable test data.
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Lower Secondary
Computing
8
Deliver an exciting computing course for ages 11–14, building on students’ existing computing
skills and experience whilst demonstrating new concepts, with practice opportunities to ensure
progression.
● Recap and activate students’ prior knowledge with ‘Do you remember?’ panels and introduce more
advanced skills with ‘Challenge yourself!’ tasks.
● Allow students to demonstrate their knowledge creatively with engaging end of unit projects that apply
skills and concepts in a range of different contexts.
● Develop computational thinking with an emphasis on broadening understanding throughout the activities.
● Provide clear guidance on e-safety with a strong focus throughout.
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