1. Learn… Create… Program

2. What is Scratch?
Scratch is a free programmable toolkit that enables kids to
create their own games, animated stories, and interactive art
share their creations with one another over the Internet.
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3. What is Scratch?
Scratch builds on the long tradition of Logo and LEGO/Logo, but takes advantage of new computational ideas and capabilities to make it easier for kids to get started with programming (lowering the floor) and to extend the range of what kids can create and learn (raising the ceiling).
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4. What is Scratch?
The ultimate goal is to help kids become fluent with digital media, empowering them to express themselves creatively and make connections to powerful ideas.
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5. What is Scratch? Increase student skills with computers
Increase student interest in programming
Student achievement on fun project
Learn Cartesian coordinates, distance computations, etc.
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6. Computer scientists Create solutions to problems using computers
Study information
Invent algorithms
Write programs to implement the algorithms
Reuse a lot of existing program and machine parts
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7. Start scratch and let’s go!
Click on the cat icon
Or, find “scratch” under “Programs”
When home, download from
Scratch programming environment comes up quickly
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8. Click on the “Looks” button at the top left.
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9. Major components
At right: the stage with sprite[s] or objects or actors
At left: operations and attributes for the sprites
Center: scripts or program[s] for the behavior[s] of the sprites
Your sprites are actors that you direct with your scripts
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10. Let’s implement an algorithm to average two numbers
Make a variable “number1” (click and drag and set)
Make another one “number2”
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11. Compute average first as sum
Make variable average
Drag a “set operation” to script area
Drag a + operation
Drag variables number1 and number2 to parameters
Click to execute
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12. Average script as 4 operation sequence.
Change the two numbers and click the sequence to execute the block again.
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13. But Scratch computes with multimedia – color, sound, …
Can make cartoons
Can create stories
Can create video games
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14. The “hello” script Can do it in 57 languages – java, C++, … Scratch
Easy in Scratch: select “Looks” operations and drag the “hello operation” onto your center panel.
Then double click on this “lego block”: check your sprite behavior at the right
Your very first Scratch program!
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15. Make the cat 50% larger Select “Looks” operations
Drag the “change size” operator into your script
Click and edit for a 50% change (increase)
Double click your one operation script
Did your cat sprite get 50% bigger?
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16. Scripting a sequence of ops
Do ops in the following order by dragging operation blocks into a single connected block
Say hello
Move 200 steps forward
Grow 50% bigger
Make the “meow sound”
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17. Some new operations wait (Control) move (Motion) color change (Looks)
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18. Starting a looped script
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19. Exercise: write a script to
Make the cat move along a square path
Say “hi” at all four corners
Wait 3 seconds at each corner
Change color at all four corners
Double size when back to the original starting location.
Say “That’s all folks” when done.
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20. Elements of Scratch: objects
Colors
Sounds
Locations in 2D space
Sprites
Costumes
Variables (to remember the state of things)
Events: that are broadcast for communication
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21. Elements of Scratch: control
Sequence of operations
Loops or repetition
Detecting events (key or mouse pressed, sprites overlapping each other, sprites hitting edge of stage, sensor giving value)
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22. Loop constructs in Scratch
Repeat N times
Repeat forever
Repeat forever if some condition exists (suppose I’m a sprite wandering about this lab until someone asks a question)
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23. Conditions can be checked
Do something if sprite k hits sprite m
Do something if a certain key is pressed
Do something is some variable takes a certain value
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24. Interacting with your sprite or story
Using mouse
Entering a character
Asking the user a question
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25. Sprite follows the mouse
Try changing the number of steps or the wait time.
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26. Play and examine MadLib
Choose the “file” option at the top of the window
Choose “open”, then “examples”
Choose “stories”
Choose “MadLib” and then read the authors instructions
Click OK, wait for load, click green flag
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27. About the MadLib story How many actors (sprites)?
What is the role of the girl?
How are the answers you give 'remembered' and then used in later actions?
What is the role of the little whale?
What makes the little whale flip around?
What makes the big whale spout?
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28. Sprites can interact with each other
Can detect when colors overlap in space
Can detect when sprites bump into edge of the stage
See “bouncing balls” example under Simulations under Examples
Interact with this simulation
Check out the rather complex scripts
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29. Check out the break dance
Open examples; music and dance; break dance
How does break dancing begin?
What are the roles of the sprites?
What events are in the scripts?
What should happen when the boom box is clicked?
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30. Experiment with Scratch as time permits
Try your own scripts: make moves, sounds, interactions in simple cases
Try the examples and learn what makes them work
Download Scratch on your own machine and experiment some more
Direct a story; or a simulation; or create a video game.
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