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B.A. (Mahayana Studies) 000-209 Introduction to Computer Science November 2005 - March 2006 12. Logo (Part 1). An introduction to Logo: drawing, moving, turning, repetition, and basic procedures. Overview. 1. What is Logo? 2. Installing Logo 3. Basic Commands 4. Drawing a Square

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B.A. (Mahayana Studies)000-209 Introduction to Computer ScienceNovember 2005 - March 200612. Logo (Part 1)

An introduction to Logo: drawing, moving, turning, repetition, and basic procedures.


Overview
Overview

  • 1. What is Logo?

  • 2. Installing Logo

  • 3. Basic Commands

  • 4. Drawing a Square

  • 5. More Commands

  • 6. The Repeat Command

continued

000-209 Intro to CS. 12/logo1


  • 7. Procedures

  • 8. Circle and Square

  • 9. Drawing a Triangle

  • 10. Drawing a House

  • 11. Drawing a Checkboard

  • 12. MSW Logo Examples

000-209 Intro to CS. 12/logo1


1 what is logo
1. What is Logo?

  • A programming language developed at the MIT Artificial Intelligence Lab

    • MIT = Massachusetts Institute of Technology

  • Logo is easy to learn, but powerful.

  • Logo has been used in telecommunications, multimedia, and robotics.

000-209 Intro to CS. 12/logo1


2 installing logo
2. Installing Logo

We're using MSW Logo, but there are many other Logo systems.

  • MSW Logo Website:

    • http://www.softronix.com/logo.html

  • The set-up kit (Windows installer):

    • http://www.softronix.com/download/mswlogo65.exe

  • Tutorials

    • The Great Logo Adventurehttp://www.softronix.com/download/tgla.zip

    • An Introduction to MSW Logohttp://www.southwest.com.au/~jfuller/logotut/menu.htm

continued

000-209 Intro to CS. 12/logo1


000-209 Intro to CS. 12/logo1


Msw logo in action
MSW Logo in Action

the turtle

menus

status

window

editor

turtle drawing

area

command

window

command

box

command input window

000-209 Intro to CS. 12/logo1


What is the turtle
What is the Turtle?

  • Originally, the turtle was a robot that moved around the floor when the user typed Logo commands into a computer.

  • Today, it is a picture on the Logo drawing area

    • in MSW Logo, the turtle is drawn as a triangle

000-209 Intro to CS. 12/logo1


3 basic commands
3. Basic Commands

  • forward <number>

    • the larger the number the farther the turtle will go

    • if you use a large enough number, the turtle will walk off the screen and wrap around to the other side

    • e.g. forward 40

  • back <number>

    • the turtle will move backwards

    • e.g. back 33

continued

000-209 Intro to CS. 12/logo1


  • right <number>

    • the number is how many degrees the turtle will turn right

    • e.g. RIGHT 90

      • turn the turtle to the right by 90 degrees.

  • left <number>

    • turns the turtle to the left

000-209 Intro to CS. 12/logo1


4 drawing a square
4. Drawing a Square

type these commands into

the command input window,

pressing <enter> after each

command

forward 100

right 90

forward 100

right 90

forward 100

right 90

forward 100

000-209 Intro to CS. 12/logo1


Error messages
Error Messages

  • Your input: forward 10 20

  • Your input: back

error

messages

000-209 Intro to CS. 12/logo1


5 more commands
5. More Commands

  • penup

    • causes the turtle to pick up its pen so that when it moves no line is drawn

  • pendown

    • puts the pen back down so drawing starts again

continued

000-209 Intro to CS. 12/logo1


  • setpencolor <number>

    • changes the colour of the turtle’s pen

    • e.g. setpencolor 5

      • make your turtle draw a pink line

MSW Logo has

command help

under "Index"

continued

000-209 Intro to CS. 12/logo1


  • clean

    • clears the turtle's drawing area

  • home

    • moves the turtle back to the center of the drawing area

000-209 Intro to CS. 12/logo1


Example using setpencolor
Example Using Setpencolor

forward 100

setpencolor 5

right 72

forward 100

setpencolor 14

right 72

forward 100

setpencolor 3

right 72

forward 100

setpencolor 2

right 72

forward 100

Because the turtle

turned right

72 degrees

5 times, it made

a pentagon

000-209 Intro to CS. 12/logo1


6 the repeat command
6. The Repeat Command

  • Get the turtle to do things many times, by using the repeat command.

  • e.g. repeat 4 [forward 10]

    • move the turtle forward 10 spaces, 4 times

    • the turtle will move forward 40 spaces altogether

  • In general, you type:

    • repeat <number> [ <commands> ]

000-209 Intro to CS. 12/logo1


Draw a square with repeat
Draw a Square with Repeat

repeat 4 [forward 100 right 90]

000-209 Intro to CS. 12/logo1


Using repeat
Using Repeat

  • 1.What will the following command draw?

    • repeat 3 [forward 100 left 120]

  • 2. Make a circle using the repeat command.

000-209 Intro to CS. 12/logo1


Answer 1 draw a triangle
Answer 1: Draw a Triangle

repeat 3 [forward 100 left 120]

000-209 Intro to CS. 12/logo1


Answer 2 draw a circle
Answer 2: Draw a Circle

repeat 360 [forward 1 right 1]

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7 procedures
7. Procedures

  • Add a new command to Logo by writing a procedure.

    • to <name of your procedure> <command 1> <command 2> :end

A procedure is a new command, built out of other commands

continued

000-209 Intro to CS. 12/logo1


  • For example:

    • to square repeat 4 [forward 100 right 90] end

  • The new command (procedure) is for drawing a square

    • it can be used just like other Logo commands

000-209 Intro to CS. 12/logo1


Typing in a procedure
Typing in a Procedure

  • A "To Mode" window pops up after you type to <name of procedure>

  • You enter your procedure line by line, and type end or press Cancel to finish.

continued

000-209 Intro to CS. 12/logo1


continued

000-209 Intro to CS. 12/logo1


000-209 Intro to CS. 12/logo1


A circle procedure
A Circle Procedure

  • The program:

    • to circle repeat 360 [forward 2 right 1] end

  • Test it out:

    • circle

000-209 Intro to CS. 12/logo1


The edall button
The Edall Button

  • To add more procedures, or change one you've already written, click on the Edall button.

000-209 Intro to CS. 12/logo1


Using edall
Using Edall

  • Enter a procedure for drawing a purple pentagon:

    • to pentagon setpencolor 10 repeat 5 [forward 75 right 72] end

  • In the Editor "File" menu, select "Save and Exit" when you are finished.

000-209 Intro to CS. 12/logo1


A pentagon
A Pentagon

000-209 Intro to CS. 12/logo1


Saving procedures
Saving Procedures

  • If want to use the procedures some other time, you should save them.

000-209 Intro to CS. 12/logo1


8 circle and square
8. Circle and Square

  • How would you write the procedure circle_and_square to make a drawing that looks like this?

  • The triangle is the position of the turtle at the end of the procedure.

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Procedure
Procedure

  • to circle_and_square home clean repeat 360 [forward 2 right 1] forward 50 repeat 3 [left 90 forward 100] left 90 forward 50 end

  • Now change circle_and_square so it uses the circle procedure.

  • continued

    000-209 Intro to CS. 12/logo1


    A procedure calls

    another procedure.

    circle_and_square

    calls

    circle

    000-209 Intro to CS. 12/logo1


    9 drawing a triangle
    9. Drawing a Triangle

    • We want a procedure that draws a triangle with a flat base.

    • This requires different turnings of the turtle:

    start

    120

    30

    120

    90

    000-209 Intro to CS. 12/logo1



    10 drawing a house
    10. Drawing a House

    • A simple house is a square with a triangle on top of it.

    • After drawing the square, the turtle must move to the start of the triangle.

    • After drawing the triangle, the turtle must move back to its original position.

    000-209 Intro to CS. 12/logo1



    Procedure calls
    Procedure Calls

    square

    house

    calls

    triangle

    000-209 Intro to CS. 12/logo1


    11 drawing a checkboard
    11. Drawing a Checkboard

    • We're going to write a series of procedures that help us make a checkboard.

    • A checkboard is a series of columns.

    • A column is a series of squares.

    • A square is made from 4 corners.

    000-209 Intro to CS. 12/logo1


    Procedure calls1
    Procedure Calls

    • I'll write four procedures, that call each other in a chain.

    checkboard

    column

    square

    corner

    calls

    000-209 Intro to CS. 12/logo1


    Drawing a corner
    Drawing a Corner

    • We want a procedure that draws a straight line, then turns 90 degrees to the right.

    • to cornerforward 20right 90end

    000-209 Intro to CS. 12/logo1


    Where did the turtle go
    Where did the Turtle Go?

    • hideturtle

      • make the turtle invisible

      • drawing still occurs, but with no turtle

    • showturtle

      • makes the turtle visible again

    000-209 Intro to CS. 12/logo1


    Drawing a square with corners
    Drawing a Square with Corners

    • A square is four calls to corner:

    000-209 Intro to CS. 12/logo1


    Drawing a column with squares
    Drawing a Column with Squares

    • A column is eight squares, followed by the turtle moving back to its starting position.

    • After drawing a square, the turtle needs to move up by 20 to get to the starting position for the next square.

    start

    start

    continued

    000-209 Intro to CS. 12/logo1



    Drawing a checkboard with columns
    Drawing a Checkboard with Columns

    • A Checkboard is eight columns.

    • After drawing a column, the turtle must move right to the starting position for the next column.

    • At the end of drawing the checkboard, the turtle should move back to the lower-left corner of the checkboard.

    000-209 Intro to CS. 12/logo1



    12 msw logo examples
    12. MSW Logo Examples

    Examples/Misc/curves.lgo

    continued

    000-209 Intro to CS. 12/logo1


    Examples/3D/Hilbert.lgo

    continued

    000-209 Intro to CS. 12/logo1


    Examples/3D/solar.lgo

    continued

    000-209 Intro to CS. 12/logo1


    Examples/Misc/clock.lgo

    continued

    000-209 Intro to CS. 12/logo1


    Examples/Windows/calc.lgo

    000-209 Intro to CS. 12/logo1


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