Logo Lesson 2 Logo Procedures

1. Logo Lesson 2Logo Procedures TBE 540-40 Fall 2004 Farah Fisher

2. Lesson Prerequisites Before beginning this lesson, the student must be able to… • Start the Logo program (appropriate version) • Create simple shapes using FD, BK, LT, RT, REPEAT • Use pen control commands such as PU, PD, PE, PPT (PP) • Change pen color and background color using SETPC or SETBG or a menu

3. Lesson Objectives After completing this lesson, the student will be able to… • Explain the concept of Logo procedures • Create a new Logo procedure • Edit an existing Logo procedure • Execute (run) a Logo procedure • Save and load workspaces • List all procedures in a workspace using POTS

4. What is a Logo procedure? • When you used Logo in Lesson 1, each time you typed a command (or set of commands), the turtle moved immediately. • However, the turtle did not “remember” how to make the shape. To create the shape again, you needed to type the commands again. • A procedure is a way to make the turtle remember a set of commands.

5. What is a Logo procedure? • Each procedure is given a name (e.g., SQUARE or HOUSE or BIG.RED.THING). The name may not include spaces. • Creating the procedure is like teaching the Logo turtle the meaning of a word. • For example, we can teach the turtle that the word SQUARE means REPEAT 4 [FD 50 RT 90] • Afterwards, every time we type the word SQAURE, the turtle will know what to do.

6. What is a Logo procedure? • Procedures are kept in memory as part of a Logo workspace. • The workspace is a collection of all the Logo procedures currently in memory. • These workspaces can be save and loaded, just like other documents. • More information about workspaces will be presented later.

7. How do you create a procedure? • Various versions of Logo may ask that you begin procedures in different ways. • This lesson will show two of the most common ways to start making a procedure. • Check the manual or HELP function of your version of Logo for more information.

8. Creating a Procedure using TO • All Logo procedures actually have the word TO as part of the name (e.g., TO SQUARE or TO HOUSE). • All versions of Logo allow this method for creating procedures. • To begin a procedure, type the word TO and a name for the procedure. • For example, you could type TO MY.NAME or TO TRIANGLE

9. Creating a Procedure using TO • You will see a symbol like this: > • The symbol means “it is your turn to type something”. • Type one or more Logo commands and press Return/Enter. Another > will appear. • After you have finished all commands, type END at the > symbol. • NOTE: You cannot immediately edit a previous line using this method. You must edit later.

10. Creating a Procedure using EDIT • All versions of Logo allow you to edit an existing procedure using the command EDIT. • Some versions of Logo also allow EDIT to be used to create new procedures (check your HELP file or manual). • To begin a new procedure or edit an old one, type the word EDIT, a quote and the procedure name. Example: EDIT “SQUARE

11. Creating a Procedure using EDIT • There are several things to notice when using the EDIT command (e.g., EDIT “HOUSE.BOAT) • There is a space after the word EDIT. • There is no space between the quote and the name of the procedure. • There is no quote after the procedure name. • Many Logo commands follow this pattern.

12. Creating a Procedure using EDIT • You will probably see the following two lines in the editing window when you begin a new procedure: • TO SQUARE (or whatever you specified as the name) • END • You will be typing the commands between these two lines, so you may need to press Return/Enter to open up space to type.

13. Creating a Procedure using EDIT • Finishing and saving a procedure using EDIT will depend on the version of Logo you are using. • There may be a menu item such as “Save and Exit”. • There may be a specific command on the keyboard. • The simplest way is to attempt to close the editing window. The computer should ask if you want to save the changes.

14. The Logo Workspace • Earlier in this lesson, a workspace was defined as a collection of procedures in memory. • Every time you create and save a procedure, it becomes part of the current workspace. • NOTE: Saving a procedure does not put it on a disk. It exists only in memory until the entire workspace is saved.

15. The Logo Workspace • The POTS command (Print Out Titles) shows you a list of all the procedures in memory. • In the list, each procedure name will have the word TO in front of it. For example (the ? is the prompt in most Logo versions - no need to type it): ? POTS TO SQUARE TO TRIANGLE TO HOUSE

16. Saving a Logo Workspace • To save a workspace on disk (including all procedures in memory), type SAVE “filename • The filename may be anything that is appropriate for your operating system. In some versions of Logo, an extension of .LGO will be added to the end of the filename. • There may be a menu item for SAVE in some versions of Logo.

17. Loading a Logo Workspace • To load a workspace that has previously been saved to disk (including all procedures in memory), type LOAD “filename • All procedures will come into memory. If some procedures are in memory before the LOAD, the new ones will simply be added to the POTS list. • There may be a menu item for LOAD in some versions of Logo.

18. Summary of Steps to Create a Logo Procedure • Decide what commands will be included in your Logo procedure and think of a name for it (with no spaces) • In your Logo program, do one of the following: • Type TO and the procedure name (TO SQ) • Type EDIT “ and the procedure name (EDIT “SQ) • Enter the commands in the procedure.

19. Summary of Steps to Create a Logo Procedure • When you have finished the procedure, exit and save using one of these methods: • If you began with TO, type END on the last line. • If you began with EDIT, close the window and save (or use the appropriate menu choice or keys) • Your procedure will become part of the POTS list.

20. Summary of Steps to Create a Logo Procedure • Create other procedures as necessary. • Remember to SAVE the workspace on disk so that you can use it again (e.g., SAVE “FIRST)

21. “Running” a Logo Procedure • After you have created a procedure, you will want to see if it works. • Type the name of the procedure (without TO) to begin. • For example, if the procedure is listed as TO THING, type THING to start the procedure. • Use EDIT “procedurename to correct mistakes.

22. Procedure Names as Logo Commands • After you have created a Logo procedure, you can use its name as a command in another procedure. NOTE: The procedure name you use must be in the current POTS. • For example, if you have created a procedure called TO SQUARE, you can include the command SQUARE in a procedure called TO HOUSE.

23. Procedure Names as Logo Commands • Example: TO TRIANGLE REPEAT 3 [FD 50 RT 120] END TO WINDMILL REPEAT 4 [TRIANGLE RT 90] END

24. Self Check for Lesson 2 • A Logo procedure is… • A shape that you make with the turtle. • A set of commands stored together under one name. • A logo command (e.g. PROCEDURE 7)

25. Self Check for Lesson 2 • A Logo procedure is… • A shape that you make with the turtle. • A set of commands stored together under one name. • A logo command (e.g. PROCEDURE 7)

26. Self Check for Lesson 2 • To begin entering a Logo procedure called GREEN, you should type… • BEGIN “GREEN • EDIT “GREEN • TO GREEN

27. Self Check for Lesson 2 • To begin entering a Logo procedure called GREEN… • Type BEGIN “GREEN • EDIT “GREEN {Most version of Logo • TO GREEN allow either of these.}

28. Self Check for Lesson 2 • After creating the procedure called GREEN, to start it you would type… • BEGIN “GREEN • “GREEN • GREEN • RUN “GREEN

29. Self Check for Lesson 2 • After creating the procedure called GREEN, to start it you would type… • BEGIN “GREEN • “GREEN • GREEN Just type the procedure name • RUN “GREEN

30. Self Check for Lesson 2 • When you type POTS, you see… • A list of all procedures in memory. • A picture of a pot. • A list of all files on the disk. • A list of all possible Logo commands

31. Self Check for Lesson 2 • When you type POTS, you see… • A list of all procedures in memory. • A picture of a pot. • A list of all files on the disk. • A list of all possible Logo commands

32. Self Check for Lesson 2 • When you type SAVE “BASICS • The procedure called BASICS is saved on the disk. • The picture called BASICS is saved on the disk. • All the procedures in POTS are saved on the disk in one file called BASICS. • Each of the procedures in POTS is saved on the disk under its own name.

33. Self Check for Lesson 2 • When you type SAVE “BASICS • The procedure called BASICS is saved on the disk. • The picture called BASICS is saved on the disk. • All the procedures in POTS are saved on the disk in one file called BASICS. • Each of the procedures in POTS is saved on the disk under its own name.

34. Self Check for Lesson 2 • To get the procedures in the BASICS file back into POTS (the workspace), type • UNSAVE “BASICS • GET “BASICS • LOAD “BASICS • You cannot retrieve the files once they have been saved.

35. Self Check for Lesson 2 • To get the procedures in the BASICS file back into POTS (the workspace), type • UNSAVE “BASICS • GET “BASICS • LOAD “BASICS • You cannot retrieve the files once they have been saved.

36. Try some Logo procedures • See the hands-on exercise at http://www.csudh.edu/fisher/tbe540/LEX2.htm • Possible answers are found at http://www.csudh.edu/fisher/tbe540/HO2ans.htm