An intro to programming
concepts with Scratch
Quick intro for college citizens.
George Stockman
MSU CSE
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A 10-minute PR clip
sallyAndHorse.sb
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What can we do with Scratch?
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Learn some computing concepts.
Learn some practical algorithms.
Have fun with Scratch creating stories,
games, art.
We are teaching Scratch after school to
middle school kids with the goal of
increasing interest in STEM.
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Start scratch and let’s go!
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Click on the cat icon
If not on desktop, download
from www.scratch.mit.edu
Scratch programming
environment comes up quickly
We will first do simple ops
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Scratch environment
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Stage is at upper right (where actors act and
information is displayed)
Sprite is another name for actor (object).
Instruction menus/panel at left (instructions
for the actors)
A script is another name for program or
method; a script tells the actor what to do.
Programming panel in center; here is where
we construct scripts for the sprites
(Sprites are objects; their scripts are methods
or behaviors.)
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We start with the cat sprite
We will learn to use other sprites
and many sprites LATER. Now we
use the cat as our only actor.
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The LOOKS menu
Has operations for setting the color,
size, and visibility of a sprite.
Constumes will be used LATER
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The “hello” script (program)
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Double click on the “say hello” lego block
Check your sprite behavior at the right
Then double click “say hello for 2 secs”
Your very first Scratch program!
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Try some other looks
operations (double click items)
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Change color effect by 25
Change color effect by 25 again
Hide
Show
Change size by 10
Change size by 10 again
Set size to 100%
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Let’s write a script to
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Say “hello” for 2 seconds
Then change color by 25
Then think “Hmm..” for 4 seconds
Then change color by 75
Then change size by 200
Drag the instructions from the menu to the center panel.
Connect them into a single block. Edit the parameters to
get the numbers we want.
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Our script (program)
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The WAIT instruction
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is needed to slow down the acting so
we can see or hear it properly
(computers are too fast sometimes)
Get the wait instruction from the
CONTROL menu. Please ignore the
other menu options at this time.
Insert a wait in our looks script
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3 second pause between
changing color and size
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The MOTION menu
How to locate and orient a sprite;
position and angle; moving a
sprite
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Position on the stage
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Drag your cat
around and note its
x-y position.
Using the Looks
menu, shrink
our cat to 25%.
Click on the
Motion menu.
Click to check
the box for xposition and yposition
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Other instructions
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goto x,y
glide to x,y
Move N steps
Set direction
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The “glide-to” instruction
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Drag the “glide-to” instruction into your
script panel.
Edit in some coordinate values and
double click to see where your sprites
goes.
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The SENSING menu
Getting information from the user
or some other machine
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Use the SENSING menu
1) Ask the user for age; 2) user types in age;
3) result stored in “answer”
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User types “13” and the script
stores the answer
“answer”
is a
Special
Scratch
variable
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OUTPUT: Giving the user
information with say answer
Say is in Looks menu;
drag “answer” from
Sensing menu; click
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Making an “age variable”
1) Click Variables menu; 2) click “Make a variable”
3) Type in “age” and click OK
Do you want to
display for all
sprites or just one?
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We have an “age variable”
Operations for “age”
Displaying variable “age”
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We can join text and a
number to say things
From Looks
From Operators
From Sensing
Make the join
Build this instruction from
the parts above it.
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Storing a value in a variable;
then saying it to the user
1) Set from Variables menu; 2) Say from Looks menu; 3) Join from the
Operators menu joins your text with the “answer”
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A first “program” for 6th grade
The variable V now stores the computed average of A and B
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Changing costumes
Another way to change the
appearance of a sprite.
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Making a new costume
1) Get bat2-a sprite from
the “sprite box”.
2) Click on sprite
3) Click on “Costumes”
4) Click on “Import”
5) Now get bat-2b sprite
from the sprite box
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Use a loop to make the bat fly!
1) When and repeat from Control menu and 2) next costume from
Looks menu.
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Changing coordinates
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We can randomly set the location of the
bat so it will “flutter”.
Set X to a random number
Set Y to a random number
Move the bat to location (X,Y)
Of course, the bat should remain on
stage!
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Using pick random
Click the stop sign at the stage upper right to stop the forever loop.
Do we need a wait in the loop? Try it to see the change in flying.
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Multiple interactive bat flight
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Adding a background
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Click on the
Stage icon at
lower right
Click on
Backgrounds
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Click on bat
icon (Sprite1)
Click on
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FLY AGAIN!
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Scripts
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Controlling the bat’s direction
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Let’s create multiple scripts.
Click space bar for random moves
Click right arrow to move right
Click left arrow to move left
The bat will behave differently
depending upon which key is typed!
(So, could a gamer catch the bat?)
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On to multimedia, games,
stories
Detecting events;
sending messages;
using music and audio;
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See stock example: Mad Lib
Explore the available examples;
Mad Lib under stories;
Study message sending;
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Study Break Dance
Music and dance example;
Messaging;
Use of stock music and costumes
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Digitizing your own audio
Use din example
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Composing with drum beats
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Jodi jumps on the drum
Story teller script
Jodi’s script
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Recording from a mike (or an
iPod or other music player)
1. Plug in microphone
2. Pick the speaker sprite
3. Click “Sounds”
4. Click “Record”
5. Click red button and speak
6. Click square button to stop
7. Click triangle to hear it
8. Click “OK” if it’s OK
9. Use name of sound in a play-sound
instruction
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Where does all this lead?
Definitely engaging for grades 6,7,8.
Does it increase STEM interest of our kids?
Does it motivate college computing classes?
Does Scratch make a smarter Lego bot?
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