Transcript An intro to Scratch

An intro to programming
concepts with Scratch
Session 1
of 10 sessions
Looks and Motion
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What are our course goals?
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Learn some computing concepts.
Learn some practical algorithms.
Use Scratch as computing tool.
Have fun with Scratch creating stories,
games, art.
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Who computes?
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Scientists
Engineers
Businessmen
Social scientists
Artists
FBI agents
Brain surgeons
Grandkids
Everyone uses
information in
some way.
Computers do
information
processing.
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Session I goals
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Intro to computer science and
programming
Scratch programming environment
Using the looks and motion menus
Writing a sequence of instructions
Positions in 2D; angles and directions
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What is needed
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Students need to have computers with
Scratch installed: 1 or 2 students per
computer
Workbook for each student
[optional] Angle display board
[optional] display of Scratch interface
with names of parts
[optional] thumb drive with examples
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“programming a robot”
Student gives instructions to robot
(instructor) to navigate around
the room
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Session I B: Scratch intro
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Brief introduction to Scratch
5 minute video
How we “program” in Scratch
The parts of the environment
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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.
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 area in center; here is where
we construct scripts for the sprites
(Sprites are objects; their scripts are
methods.)
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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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Choose the Looks menu
Click on the “say hello” lego block
Check your sprite behavior at the right
Then click “say hello for 2 secs”
Your very first Scratch program!
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Try some other looks
operations (click menu 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 each instruction from the menu to the center
script area. 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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A sequence or block is a
simple script or program
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The first instruction is done first
The second instruction is done second
The last instruction is done last.
(if any one instruction is done, then
every on of them is done)
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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. 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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Student exercise: write a
script to do the following
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Double the size of the sprite
Wait 2 seconds
Change the color of the sprite to green
Wait 4 seconds
Change the whirl effect to 100
Say “That’s all folks!”
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The MOTION menu
How to locate and orient a
sprite; location 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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Exercises: goto instruction
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In the Motion menu, drag the “goto xy”
instruction to the script panel.
Edit the coordinates and click to see the
sprite’s position
A) goto x=200, y=0
Where does
the cat go?
B) goto x=-200, y=0
C) goto x=200, y=-100
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The “glide-to” instruction
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Drag the “glide-to” instruction into
your script panel.
Edit the coordinate values and click
to see where your sprites goes.
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Exercise
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Create a script to glide the sprite along
the sides of a triangle. The first vertex
of the triangle is (-100, -100). The
second vertex is (200, -100). The third
vertex is (50, 100). Make sure you
complete the triangle.
Change the speed of gliding and run
again.
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Angles and directions
Making your sprite
go this way and
that way
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Angles are important
180 degrees
About 30
degrees
About 45
degrees
(straight angle)
215 deg
90 degrees
(right angle)
360 deg
complete
circle
http://www.mathsisfun.com/geometry/degrees.html
To see animation of angle measure.
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Using a protractor to measure angles
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Measure some angles with a
protractor
C
Q
P
B
A
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Set direction and move
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Choose Motion menu
Click on turn 15 degrees
Repeat
Click on move 10 step
Repeat
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The treasure is buried under an oak tree
42 degrees to the right of the line
between the statue and post
post
42
deg
statue
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Exercise: write a script
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Start at ( -100, 100 )
Move 200 steps
Turn right 90 degrees
Move 200 steps
Turn right 90 degrees
Move 200 steps
Turn right 90 degrees
Move 200 degrees
Use waits if
needed to make
the motion look
smooth
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Individual achievement:
student creates/demonstrates
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Sprite starts at home base at x=-100; y=-50
Sprite says “I hit the ball” for 2 seconds
Sprite runs (east) 200 steps to 1st base
Sprite changes color
Sprite runs 200 steps to 2nd base (north: left
turn from 1st base)
Sprite doubles size
Sprite says “I hit a double” for 5 seconds
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End of session I
Student should be able to control the looks
of a sprite and its location on the stage.
Students should be able to construct
sequences of instructions controlling looks
and location on the stage.
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