1. 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.

2. 000-209 Intro to CS. 12/logo1 2 Overview 1. What is Logo? 2. Installing Logo 3. Basic Commands 4. Drawing a Square 5. More Commands 6. The Repeat Command continued

3. 000-209 Intro to CS. 12/logo1 3 7. Procedures 8. Circle and Square 9. Drawing a Triangle 10. Drawing a House 11. Drawing a Checkboard 12. MSW Logo Examples

4. 000-209 Intro to CS. 12/logo1 4 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.

5. 000-209 Intro to CS. 12/logo1 5 2. Installing Logo 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 Adventure http://www.softronix.com/download/tgla.zip  An Introduction to MSW Logo http://www.southwest.com.au/~jfuller/logotut/menu.htm continued We're using MSW Logo, but there are many other Logo systems.

6. 000-209 Intro to CS. 12/logo1 6 Double click on mswlogo65.exe to start the installation. The program will be added to the start menu as "Microsoft Windows Logo".  called MSW Logo The MSWLogo directory contains an Examples/ folder (see end of these slides).

7. 000-209 Intro to CS. 12/logo1 7 MSW Logo in Action turtle drawing area the turtle editor command window command input window status window menus command box

8. 000-209 Intro to CS. 12/logo1 8 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

9. 000-209 Intro to CS. 12/logo1 9 3. Basic Commands forward  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  the turtle will move backwards  e.g. back 33 continued

10. 000-209 Intro to CS. 12/logo1 10 right  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  turns the turtle to the left

11. 000-209 Intro to CS. 12/logo1 11 4. Drawing a Square forward 100 right 90 forward 100 right 90 forward 100 right 90 forward 100 type these commands into the command input window, pressing after each command

12. 000-209 Intro to CS. 12/logo1 12 Error Messages Your input: forward 10 20 Your input: back error messages

13. 000-209 Intro to CS. 12/logo1 13 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

14. 000-209 Intro to CS. 12/logo1 14 setpencolor  changes the colour of the turtle’s pen  e.g. setpencolor 5 make your turtle draw a pink line continued MSW Logo has command help under "Index"

15. 000-209 Intro to CS. 12/logo1 15 clean  clears the turtle's drawing area home  moves the turtle back to the center of the drawing area

16. 000-209 Intro to CS. 12/logo1 16 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

17. 000-209 Intro to CS. 12/logo1 17 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 [ ]

18. 000-209 Intro to CS. 12/logo1 18 Draw a Square with Repeat repeat 4 [forward 100 right 90]

19. 000-209 Intro to CS. 12/logo1 19 Using Repeat 1.What will the following command draw?  repeat 3 [forward 100 left 120] 2. Make a circle using the repeat command.

20. 000-209 Intro to CS. 12/logo1 20 Answer 1: Draw a Triangle repeat 3 [forward 100 left 120]

21. 000-209 Intro to CS. 12/logo1 21 Answer 2: Draw a Circle repeat 360 [forward 1 right 1]

22. 000-209 Intro to CS. 12/logo1 22 7. Procedures Add a new command to Logo by writing a procedure.  to : end A procedure is a new command, built out of other commands continued

23. 000-209 Intro to CS. 12/logo1 23 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

24. 000-209 Intro to CS. 12/logo1 24 Typing in a Procedure A "To Mode" window pops up after you type to You enter your procedure line by line, and type end or press Cancel to finish. continued

25. 000-209 Intro to CS. 12/logo1 25 After typing repeat 4 [forward 100 right 90] end continued

26. 000-209 Intro to CS. 12/logo1 26 Executing the procedure:  square

27. 000-209 Intro to CS. 12/logo1 27 A Circle Procedure The program:  to circle repeat 360 [forward 2 right 1] end Test it out:  circle

28. 000-209 Intro to CS. 12/logo1 28 The Edall Button To add more procedures, or change one you've already written, click on the Edall button.

29. 000-209 Intro to CS. 12/logo1 29 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.

30. 000-209 Intro to CS. 12/logo1 30 A Pentagon

31. 000-209 Intro to CS. 12/logo1 31 Saving Procedures If want to use the procedures some other time, you should save them.

32. 000-209 Intro to CS. 12/logo1 32 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.

33. 000-209 Intro to CS. 12/logo1 33 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

34. 000-209 Intro to CS. 12/logo1 34 A procedure calls another procedure. circle_and_square circle calls

35. 000-209 Intro to CS. 12/logo1 35 9. Drawing a Triangle We want a procedure that draws a triangle with a flat base. This requires different turnings of the turtle: start 3030 120 9090

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37. 000-209 Intro to CS. 12/logo1 37 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.

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39. 000-209 Intro to CS. 12/logo1 39 Procedure Calls house square calls triangle

40. 000-209 Intro to CS. 12/logo1 40 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.

41. 000-209 Intro to CS. 12/logo1 41 Procedure Calls checkboardcolumn calls squarecorner I'll write four procedures, that call each other in a chain.

42. 000-209 Intro to CS. 12/logo1 42 Drawing a Corner We want a procedure that draws a straight line, then turns 90 degrees to the right. to corner forward 20 right 90 end

43. 000-209 Intro to CS. 12/logo1 43 Where did the Turtle Go? hideturtle  make the turtle invisible  drawing still occurs, but with no turtle showturtle  makes the turtle visible again

44. 000-209 Intro to CS. 12/logo1 44 Drawing a Square with Corners A square is four calls to corner:

45. 000-209 Intro to CS. 12/logo1 45 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 continued

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47. 000-209 Intro to CS. 12/logo1 47 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.

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49. 000-209 Intro to CS. 12/logo1 49 12. MSW Logo Examples Examples/Misc/curves.lgo continued

50. 000-209 Intro to CS. 12/logo1 50 Examples/3D/Hilbert.lgo continued

51. 000-209 Intro to CS. 12/logo1 51 Examples/3D/solar.lgo continued

52. 000-209 Intro to CS. 12/logo1 52 Examples/Misc/clock.lgo continued

53. 000-209 Intro to CS. 12/logo1 53 Examples/Windows/calc.lgo