MSW Logo

Book Two

Rose Bay High School

Revision of Book One

Entering MSW Logo Commands

MSW Logo is an "interpreted" language. This means that commands issued by the user are interpreted by the computer and acted upon immediately, one statement at a time. "Compiled" programs, on the other hand, are first converted into machine language as an entire unit before any part of the program can be 'run'.

Commands are entered in the Input Box in the Commander window at the bottom of the screen.

Commands are executed, after being entered in the Input Box, by either pressing the Return key, or clicking on the Execute button. Each command is recorded in the Output/Command-Recall List Box above the Input Box.

A Typical Logo Program Screen Dimensions

To exit MSW Logo enter BYE in the Input Box, or select Exit from the File menu.

Summary of Selected MSW Logo Commands

Command	Action	Short Version
FORWARD 100	Turtle moves forward the specified number of units.	FD 100
BACK 50	Turtle moves back the specified number of units.	BK 50
RIGHT 90	Turtle turns clockwise the number of degrees specified.	RT 90
LEFT 45	Turtle turns counterclockwise the angle specified.	LT 45
PENUP	Turtle's pen is up. (Doesn't draw as it moves.)	PU
PENDOWN	Turtle's pen is in the down position.	PD
PENERASE	Turtle erases as it moves.	PE
HIDETURTLE	Removes the Turtle 'triangle' from the screen.	HT
SHOWTURTLE	Makes the Turtle visible again.	ST
CLEARSCREEN	Erases the screen and returns the Turtle to its "home" position in the centre of the drawing screen.	CS
HOME	Returns the Turtle to the "home" position without erasing the screen. (Issue a PU command before HOME to prevent it drawing its return path as it goes.)	HOME
LABEL [HELLO WORLD]	Displays text at the Turtle location.	-
SETPENCOLOR 1-15	Determines pen color according to: SETPC 4 = Red SETPC 2 = Green SETPC 1 = Blue	- -
SOUND [1000 200]	SOUND [<frequency> <duration>] where “frequency” is in cps and “duration” is in 1000ths of a second.
SETPENSIZE [10 10]	Sets width and height of the drawing pen. MSW Logo uses only the second value. Set them both the same.	- --
BYE	Exits MSW Logo	-

Writing Procedures in the Editor Window:

If you define a procedure via the Input Box by typing in: to box, the input dialogue window appears where you enter one line at a time followed by <Enter>. You are prompted to type in “End” to end the procedure.

A better approach for editing is to use the built-in Editor window…

1. Go to the File/Edit… menu

2. Type in a suitable procedure name and click the OK button. The Editor window appears…

You can type in commands, edit them, cut and paste, just like a conventional word processor. When you have finished defining the procedure go to File/Exit and click the Yes button to save your work..

Remember that nothing has been saved to disk until you do a File/Save.

Saving Your Work in MSW Logo:

The File/Save and File/Save As… menus can be used to save logo files in the usual way, BUT this will only save work that has been defined as procedures. MSW Logo will save ALL of the procedures you defined during the ‘session’ as a file with the extension .LGO. The programme does NOT save individual procedures as separate files. All the procedures you created will be saved. You will lose all of the commands typed directly into the Input Box that were not defined as part of a procedure. (Another great reason for using procedures!)

Activity 1

1. Write the procedure below in MSWlogo’s editor.

To wow
CS HT
REPEAT 100 [FD 20 RT REPCOUNT REPEAT 3 [FD 60 RT 120]]
END

2. Save your work to your user directory.

· Click on File/Save as

· Find your user directory on U: drive.

Loading Previously Saved Sessions:

The File/Load menu allows you to reload procedures you have previously defined. Only those files with a “.LGO” extension will listed in the dialogue box. If you want to load a file created with a text editor and saved without the .LGO extension select All Files (*.*) from the Files of Type: box.

WARNING: Loading a file will overwrite any procedures from the current session of the same name. ie If you have just defined a procedure called MyPicture and the file you load also has a procedure called MyPicture, the current one will be overwritten by the one contained in the file and you will lose all of the commands defined within the current version.

Activity 2

1. Close MSWlogo

2. Open MSWlogo

3. Load the work you saved in Activity 1.

· Click on File/Load.

· Find your user directory and click on the filed you saved.

· Run the procedure wow

******To Print Your Work Click On BITMAP/PRINT******

Activity 3

1. Make a copy of the table below in Word using copy / paste from the Intranet version of this document. Print out the table.

2. Copy all of the procedures in the table into the MSWlogo editor.

3. Run each in turn.

4. Draw a copy of the shape produced in the right hand column of the table. Put your completed table into your flip file.

TO PIC1 REPEAT 4 [ FD 20 RT 90] END
TO PIC2 REPEAT 60 [ FD 1 RT 6] END
TO PIC3 MAKE "SIDE 1 REPEAT 240 [FD :SIDE RT 10 MAKE "SIDE :SIDE+.01] END
TO PIC4 MAKE "SIDE 1 REPEAT 120 [FD :SIDE RT 10 MAKE "SIDE :SIDE*1.015] END
TO PIC5 REPEAT 10 [PIC1 RT 60] END
TO PIC6 REPEAT 6 [REPEAT 3 [FD 20 RT 120] RT 60] END
TO PIC7 FD 10 RT 120 FD 20 RT 120 FD 30 RT 120 FD 40 END
TO PIC8 MAKE "X 1 REPEAT 20 [FD :X RT :X BK :X MAKE "X :X+2] END
TO PIC9 REPEAT 10 [PIC1 RT 36] END
TO PIC10 REPEAT 2 [LT 90 FD 20 LT 90 FD 100] END

Using Variables in MSW Logo

A variable can be thought of as a ‘container’ for different values. You can change the value of a variable at any time.

MSW Logo uses a statement in the form: make “MyVariable 20 to assign a value to a variable.

The value of the variable is accessed in the form: label :MyVariable (NOTE: the colon in front of the variable name.)

to multiply
   make “Number1 16
   make “Number2 3
   make “Answer :Number1 * :Number2
   label :Answer
end

IMPORTANT – You need to understand the difference between using a variable and ordinary text. When accessing a variable’s value you must put a colon in front of the variable name.

Eg. LABEL hello will produce – hello

Whereas

Make “hello 79

LABEL :hello will produce – 79

LABEL hello * 2 will produce an error

Whereas

LABEL :hello * 2 will produce 158

Passing Values into Procedures

to box :size
Repeat 4 [fd :size rt 90]
end

The size of the box can be determined by the value typed in when running the procedure.

Eg box 20, box 40 , etc.

NOTE: If you type in box, without the value, MSW Logo will report an error.

Activity 4

Fun With Repeat

1. Type the procedure “box” (previous page) into the MSWlogo editor.

Test it by calling it with different values for :size.

Eg. box 50

Box 100

Box 150

Now try these cool programs.

· REPEAT 100 [BOX REPCOUNT RT 10]

· CS REPEAT 20 [FD 100 RT 170]

· CS REPEAT 100 [FD 10 RT REPCOUNT]

What does the command REPCOUNT do?

You can find out by typing : REPEAT 8 [ PRINT REPCOUNT]

For more information look it up in the Help / Index.

User Input

MSW Logo is a Windows programming language. It makes extensive use of the built-in Windows “Graphical Users Interface (“GUI”). If you want to write a programme which accepts user input and then acts on it you must use the standard Windows GUI for user input.

to multiply
   ; A sample routine to demonstrate “readlist”
   ; and “first” to extract a number from user input.
   make “Number1 first readlist
   make “Number2 first readlist
   ; See the next page for an explanation of READLIST.
   make “Answer :Number1 * :Number2
   home
   cs
   ht
   print :Answer
end

READLIST (RL)

READLIST

The function “readlist” displays the dialogue box (as below) and allows the user to enter text.

The contents of the input box may be entered as a variable and manipulated by functions such as LABEL.

to writename
make “TheirName RL
label :TheirName
end

Activity 5

Write a procedure which will input three numbers and then output their sum.
Use PRINT rather than LABEL to display the answer in the procedure.
Write a procedure that will input the length of one side of a square. The program will then output both the perimeter and area of the square.
Write a procedure that will input the length of the side of a box. The procedure will then draw the box.

Activity 6

A Game of Chasings for Two

Commands to be Used

ST Show the Turtle

PU Pen up

PD PenDown

FD Forward eg FD 150 RT Right eg RT 140

Setturtle 1 Sends the next commands to turtle 1

Setturtle 0Sends the next commands to turtle 0

Wrap To keep the turtle visible

RT and LT

Setting up the Game

Player 1 in the Input Box type:

Wrap Setturtle 1 PU ST RT random 360 FD random 200

Player 2 in the Input Box type:

Setturtle 0 PU

Playing.the Game

Player 1 makes a move with two FD commands and one RT command. eg

Setturtle 1 FD 100 RT 60 FD 100

Player 2 now tries to catch the first player using only one RT command and one FD command. eg

Setturtle 0 RT 30 FD 1 50

Play continues until the chasing turtle catches the first turtle.

Activity 7

The following procedures draw a shell:

to shells :size
    square :size rt 10
    if :size > 200 [stop]
    shells :size +5
end

to square :side
repeat 4 [fd :side rt 90]
end

Enter the procedures in the editor and see the result by typing shell 5 in the input box.
Rewrite the procedures so that a triangle is spiraled to produce the pattern.
Make any other changes that you consider improve the pattern.
Print out both the procedures you have written and the pattern produced.