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# Logo Lesson 1 - PowerPoint PPT Presentation

Logo Lesson 1. TBE 540-40 Fall 2004 Farah Fisher. What is Logo?. A programming language (instructions to the computer to perform a task) Created at MIT during a study of artificial intelligence (see http://el.media.mit.edu/logo-foundation/logo/index.html )

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Logo Lesson 1

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## Logo Lesson 1

TBE 540-40

Fall 2004

Farah Fisher

### What is Logo?

• A programming language (instructions to the computer to perform a task)

• Created at MIT during a study of artificial intelligence (see http://el.media.mit.edu/logo-foundation/logo/index.html)

• Can be used by virtually any student - from young children through engineering students

• Can be used to create pictures, display text, or perform calculations. Some versions can even make music!

### What is Logo?

• When Logo is used to create pictures, commands are given to a “robot turtle”.

• Some samples of the “turtle” shape:

### What does Logo look like?

• The simplest form of Logo uses movement commands to control the “robot turtle”.

• Sample commands:

• FD (or FORWARD) moves the turtle forward

• BK (or BACK) moves the turtle backwards

• RT (or RIGHT) turns the turtle to the right

• LT (or LEFT) turns the turtle to the left

### What does Logo look like?

• FD and BK both require a number, which indicates the “turtle steps” to move (steps are very small).

• RT and LT both require the number of degrees in the turn.

• Examples (notice the space after the command):

• FD 50 (move forward 50 turtle steps)

• LT 90 (turn left 90 degrees)

### What does Logo look like?

• As the turtle moves, it leaves a “trail” on the screen.

• These “trails” make shapes.

• Imagine for a moment that you are walking around the bases of a baseball diamond, about 30 steps on each side. Assume that you are walking forward from base to base. Are you turning left or right?

• Go to the next slide when you finish.

### What does Logo look like?

• In walking around the baseball diamond in your imagination, you probably followed these steps (written as they would be in Logo):

• FD 30 (home to 1st base)

• LT 90 (turn toward 2nd base)

• FD 30 (1st base to 2nd base)

• LT 90 (turn toward 3rd base)

• FD 30 (2nd base to 3rd base)

• LT 90 (turn toward home)

• FD 30 (3rd base to home)

• Imagine that you were dragging a paint brush when you walked. What shape would you have drawn?

### What does Logo look like?

• The commands below would make a square! (turtle shown at the end)

FD 30

LT 90

FD 30

LT 90

FD 30

LT 90

FD 30

SHAPE 1

FD 30

RT 90

FD 60

SHAPE 3

FD 50

LT 60

FD 50

SHAPE 2

RT 90

FD 50

LT 90

FD 50

SHAPE 4

FD 100

RT 45

FD 50

SHAPE 1

FD 30

RT 90

FD 60

SHAPE 3

FD 50

LT 60

FD 50

SHAPE 2

RT 90

FD 50

LT 90

FD 50

SHAPE 4

FD 100

RT 45

FD 50

### The REPEAT Command

• When you “walked around the bases”, you may have noticed that the Logo commands were repeated.

• The REPEAT command is used as a shortcut in place of writing out repeated commands.

• Example: REPEAT 2 [FD 50 RT 90] is the equivalent of FD 50 RT 90FD 50 RT 90

• Notice that the number of repeats comes first, with the commands to be repeated inside square brackets.

To make a SQUARE

FD 30

LT 90

FD 30

LT 90

FD 30

LT 90

FD 30

OR…to make a SQUARE

REPEAT 4 [FD 30 LT 90]

This version actually adds another LT 90 to the list, but does not change the basic shape.

### REPEAT Example

• You have seen that REPEAT 4 [FD 30 LT 90] makes a square. Guess the shapes made by the REPEAT commands below. Click to see if you were right.

REPEAT 3 [FD 30 LT 120]

REPEAT 6 [FD 30 LT 60]

REPEAT 8 [FD 30 LT 45]

REPEAT 5 [FD 30 LT 72]

REPEAT 3 [FD 30 RT 120]

REPEAT 8 [FD 30 LT 45]

REPEAT 6 [FD 30 LT 60]

REPEAT 5 [FD 30 LT 72]

### Did you notice a pattern?

• The number after REPEAT is the number of sides.

• Examine the number of repeats and the number of degrees. Try multiplying them together. Example: 4 (sides) x 90 (turn)

• The sides x degrees should always be the same number in the samples you tried.

• Could you use this information to make a 10-sided figure? Click for a possible answer.

### Did you notice a pattern?

• REPEAT 10 [FD 30 LT 36] should make a 10-sided figure.

• Why? Look at the “total turtle turns” below:

REPEAT 3 [FD 30 LT 120] 3 x 120 = 360

REPEAT 6 [FD 30 LT 60] 6 x 60 = 360

REPEAT 8 [FD 30 LT 45] 8 x 45 = 360

REPEAT 5 [FD 30 LT 72] 5 x 72 = 360

REPEAT 10 [FD 30 LT 36] 10 x 36 = 360

• When the turtle makes a closed figure (no breaks in the sides), the total turns add up to 360 degrees.

### Logo and Critical Thinking

• You have just seen an example of the use of Logo to enhance critical thinking.

• Your students (and you, too) can be challenged to write the sequential steps needed to make shapes, look for patterns, predict outcomes…all part of critical thinking.

• Watch for more examples of critical thinking as you learn Logo.

### Changing Things

• Here is another prediction task for you.

• You have seen that to make a square, you can use REPEAT 4 [FD 30 LT 90]

• Do you think the same commands would work if you turned RT instead of LT?

• How could you make a square larger? What would you have to change?

• After you have made predictions, go to the next slide.

REPEAT 4 [FD 30 LT 90]

REPEAT 4 [FD 30 RT 90]

REPEAT 4 [FD 10 LT 90]

REPEAT 4 [FD 50 LT 90]

### Controlling the Logo “Pen”

• When the Logo turtle moves, it usually draws with a “pen”.

• This pen can be “down” (draws a line) or “up” (does not draw a line). If the pen is up, the turtle moves without drawing.

• The pen can also become an eraser (remove a line already drawn).

• The pen color abd background can be changed.

### Pen Control Commands

• PU (PENUP) - subsequent movements of the turtle will not leave a line

• PD (PENDOWN) - subsequent movements of the turtle will leave a line

• PE (PENERASE) - subsequent movements of the turtle will erase any line it crosses

• PPT or PP (PENPAINT) - used by some versions of Logo to “undo” PENERASE

### Logo Challenge

• How could you use PU and PD to make a dashed line (like the middle of a road)?

• Try making the pattern below (turtle always starts pointed “up” with the pen down):

### Logo Challenge

Two possible solutions for this shape:

RT 90 FD 25 PU FD 25 PD FD 25 PU FD 25 PD

FD 25 PU FD 25 PD FD 25

Alternate using REPEAT:

RT 90 REPEAT 4 [FD 25 PU FD 25 PD]

OR…You could draw a line and go back over it with an eraser!

(NOTE: Logo commands can be placed on the same line.)

### Logo Color

• The Logo command to set the pen color is SETPC on most versions of Logo.

• The Logo commands to set the background color is SETBG on most versions of Logo.

• Each of these commands must be followed by a number (typically from 0 to 15).

• The numbers may signify different colors in various version of Logo. You will need to experiment.

• NOTE: Some versions of Logo use a menu to choose colors.

### Logo Color

• Here are some sample commands using color.

• SETPC 0 (pen will draw in black)

• SETPC 7 (pen will draw in white - probably)

• SETBG 3 (screen background will change color)

• NOTE: If you set the pen color and the background to the same number, you will not see any drawing!

### Self-Check for Lesson 1

• Suppose you enter these commands (with the turtle starting at “home” in the middle of the screen, pointing up): FD 30 RT 90

• Which shape would appear?

### Self-Check for Lesson 1

• Suppose you enter these commands (with the turtle starting at “home” in the middle of the screen, pointing up): FD 30 RT 90

• Which shape would appear?

### Self-Check for Lesson 1

• Which of the following is a Logo shortcut for

FD 50 LT 60 FD 50 LT 60 FD 50 LT 60

• REPEAT 3 (FD 50 LT 60)

• REPEAT [LT 60 FD 50]

• REPEAT 3 [FD 50 LT 60]

• REPEAT [FD 50 LT 60]

### Self-Check for Lesson 1

• Which of the following is a Logo shortcut for

FD 50 LT 60 FD 50 LT 60 FD 50 LT 60

• REPEAT 3 (FD 50 LT 60)

• REPEAT [LT 60 FD 50]

• REPEAT 3 [FD 50 LT 60]

• REPEAT [FD 50 LT 60]

### Self-Check for Lesson 1

• Which of the following sets of Logo commands will move the turtle 50 steps without drawing?

• FD 50 PU

• PU FD 50

• PE FD 50

### Self-Check for Lesson 1

• Which of the following sets of Logo commands will move the turtle 50 steps without drawing?

• FD 50 PU

• PU FD 50 {PENUP starts no drawing} OR

• PE FD 50 {PENERASE also starts no drawing}

### Self-Check for Lesson 1

• Suppose you type these three Logo commands:

• SETBG 0 SETPC 0 FD 100

• What will you see on the screen?

### Self-Check for Lesson 1

• Suppose you type these three Logo commands:

• SETBG 0 SETPC 0 FD 100

• What will you see on the screen?

You will see the turtle in a different place, but no line. You have instructed the turtle to draw in black on a black background!

### Time to Try Logo

• Use the class CD-ROM to start Logo or download it from the website at http://www.csudh.edu/fisher/tbe540

• You should see two windows - one for commands and one to show the drawing.

FD 50

RT 90

FD 25

### Time to Try Logo

• Try the activities from Hands-On Exercise 1. This is not a graded exercise.

• Experiment with the Logo commands listed on the handout for Week 1.