Transcript tenSessionScratchL1 - Computer Science and Engineering

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
• 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 [if available]
How we “program” in Scratch
The parts of the environment
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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.
• 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.
Costumes 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
• 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
• 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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Exercises: goto instruction
• 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
• B) goto x=-200, y=0
the cat go?
• C) goto x=200, y=-100
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The “glide-to” instruction
• 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
• 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 [if available]
C
Q
P
B
A
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Set direction and move
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 steps
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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