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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?

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!

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 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)

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)

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 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

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

Using the Looks menu, shrink our cat to 25%.

Click on the Motion menu.

Click to check the box for x-position and y-position

Drag your cat around and note its x-y position.

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Other instructions

goto x,y glide to x,y Move N steps Set direction

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The “glide-to” instruction

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 menu1)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”Displaying variable “age”Operations for “age”

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We can join text and a number to say things

Build this instruction from the parts above it.

From Looks

From OperatorsFrom Sensing

Make the join

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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

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

Click on the Stage icon at lower right

Click on Backgrounds

Click on bat icon (Sprite1)

Click on Scripts

FLY AGAIN!

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Controlling the bat’s direction 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?