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

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  1. 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.

  2. 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

  3. 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

  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. 000-209 Intro to CS. 12/logo1

  5. 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

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

  7. 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

  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 000-209 Intro to CS. 12/logo1

  9. 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

  10. 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

  11. 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

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

  14. 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

  15. 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

  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 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 <number> [ <commands> ] 000-209 Intro to CS. 12/logo1

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

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

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

  22. 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

  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 000-209 Intro to CS. 12/logo1

  24. 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

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

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

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

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

  34. A procedure calls another procedure. circle_and_square calls circle 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 120 30 120 90 000-209 Intro to CS. 12/logo1

  36. 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. 000-209 Intro to CS. 12/logo1

  38. 000-209 Intro to CS. 12/logo1

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

  41. 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

  42. 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

  43. 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

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

  46. 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. 000-209 Intro to CS. 12/logo1

  48. 000-209 Intro to CS. 12/logo1

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

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