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Computing Science Scratch Programming
Computing Science
Scratch Programming
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Creating an Account
1. Access Scratch here: https://scratch.mit.edu/
2. Sign up for an account by clicking Join Scratch.
Don’t use your real name as your username.
3. Use your Glow email address:
You will have to log in to your Glow emails
Click on the link you will be sent to confirm you
Scratch account
4. If you forget your username or password, you can
click the need help button when you sign in.
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Worked
Example
1
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Worked Example 1: Using Flow Charts
What is a Flow Chart?
A flow chart is a design technique used to show the sequence of steps to be
followed by a program.
Different shapes are used to indicate different types of instruction.
Rounded rectangle:
start of a program
Rectangle:
A normal instruction
Parallelogram:
An input (type something)
Rectangle:
A normal instruction
Parallelogram:
An output (display a message)
Rounded rectangle:
start of a program
Arrows: Point to the next instructions. This shows
the sequence of steps the program will follow.
What is an Algorithm?
An algorithm is a sequence of steps that describe how to solve a problem.
The flow chart above is an example of an algorithm.
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Design
The first thing to do when creating a program is to design the steps that the program
must follow. We can do this with a flow chart.
Step 1 The program starts. Step 2 The character should be set to 100% size. Step 3 The character should turn to face the right. Step 4 The program must display a message saying “Hello World” This is called an OUTPUT. Step 5 The program plays a “Meow” sound. Step 6 The program waits for 1 second. Step 7 The character should turn to face the left. Step 8 The character size should be set to 200%. Step 9 The program ends.
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Converting Design to Code
We can now use the design we created to write the Scratch code needed to make
the program work.
You can see below how the flow chart shapes can be converted into the correct
Scratch blocks.
Flow Chart (Design) Scratch (Code)
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Task 1a
Watch the Worked Example 1.mp4 video.
Follow the instructions on the next 3 pages to:
• Write the Scratch code
• Test your program
Writing the Code: Step-by-Step Guide
Step 1
Click Find Drag it into the middle area
Step 2
Click Find Drag it into the middle area and connect it to the green flag block.
Step 3
Click Find Connect it to the size block and change its value to 90.
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Step 4
Click Find
Connect it to the direction block and change its text to “Hello World”.
Step 5
Click Find
Connect it to the say block.
Step 6
Click Find Connect it to the sound block.
Step 7
Click Find Connect it to the wait block and leave its value as -90.
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Step 8
Click Find Connect it to the direction block and change its value to 200.
Testing the Code
1. Run the program by clicking on the green flag at the top
on the stage area.
2. Check that scratch does the following:
• Size changes to 100% (run the program twice to check this)
• Turns to the right (run the program twice to check this)
• Says “hello world”
• Plays the “meow” sound
• Waits for a second
• Turns to the left
• Doubles in size
3. Try running the program again to make sure it follows .
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Saving the Code (to a computer)
1. Give the project a name that matches the name of the task.
2. Click on File – Save to your computer.
3. At the bottom of the browser, click on the arrow next to your download and click
Show in Folder.
4. Right click on the download and copy it to a folder that you keep all your
projects in (you will have to make a folder somewhere).
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Saving the Code (using a tablet or phone)
1. Give your project a name that matches the task.
2. Click on the Save Now button
3. Click on the folder icon to see your projects.
4. Select a project the click on See Inside.
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Worked
Example
2
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Worked Example 2: Colour and Turn
Read the description below of the problem we are going to solve.
Problem Description
A program is required that will do the following each time the green flag is clicked:
• Change the colour of Scratch to blue.
• Display the message, “I love coding” for 2
seconds.
• Change direction by 900 to the right.
• Change the colour of Scratch back to normal
• There should be a 1 second delay between each instruction.
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Design
The first thing to do is to design the steps that the program will follow. We can do this
with a flow chart.
Step 1 The program starts. Step 2 The program changes the character’s colour to blue. Step 3 The program must wait for 1 second. Step 4 The program must display a message saying “I love coding”. This is called an OUTPUT. Step 5 The program must wait for 1 second. Step 6 The program rotate the character by 900 to the right. Step 7 The program must wait for 1 second. Step 8 The program changes the character’s colour to back to normal. Step 9 The program ends.
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Converting Design to Code
We can now use the design we created to write the Scratch code needed to make
the program work.
You can see below how the flow chart shapes can be converted into the correct
Scratch blocks.
Flow Chart (Design) Scratch (Code)
Task 2a
• Watch the Worked Example 2.mp4 video.
• Put the code together in the order shown above connecting all the blocks
together. (You can follow the instructions on the next 2 pages to help if you need to)
THEN
• Test your program (see page 17)
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Writing the Code: Step by Step Guide
Step 1
Click Find Drag it into the middle area
Step 2
Click Find Connect it to your green flag block. Change the effect number 100.
Step 3
Click Find Connect it to the set colour block.
Step 4
Click Find
Connect it to the wait block and change the message to “I love coding”
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Step 5
Click Find Connect it to the say block.
Step 6
Click Find Connect it to the wait block. Change the degrees value to 90.
Step 7
Click Find Connect it to the turn block.
Step 8
Click Find Connect it to the wait block.
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Testing the Code
1. Run the program by clicking on the green flag at the top on
the stage area.
2. Check that scratch does the following:
• Changes colour to blue.
• Displays the message, “I love coding” for 2 seconds.
• Changes direction by 900 to face downwards.
• Changes colour back to normal.
• Waits 1 seconds between each of the above.
Test the program 4 times to check that Scratch returns to the starting position.
Save the Code
Give the project the name, Worked Example 2 and save it.
