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Introduction to Turtle Graphics

MicroWorlds 2.0 User's Guide (77 Pages) 462KB

See my MicroWorlds Logo Notes

Useful LOGO commands

	pd        ; pen down so the turtle            ; draws a line when it moves.
	cg        ; clear the screen
	fd 100    ; forward 100
	setpensize 2  ; draw with a                ; thicker line
	setpensize 5  ; draw with a                ; thicker line
	rt 90         ; turn right 90                ; degrees
	pd fd 100 rt 90 fd 50
	pd fd 100 rt 90 fd 50 rt 90 fd 100 rt 90 fd 50
	cg pd fd 50 rt 90 fd 50 rt 90 fd 50 rt 90 fd 50
	cg pd repeat 4 [ fd 50 rt 90 ]
	cg pd repeat 8 [ repeat 4 [ fd 50 rt 90 ] rt 45 ]
	cg pd repeat 36 [ repeat 4 [ fd 50 rt 90 ] rt 10 ]
	cg pd repeat 100 [ fd random 10 lt random 30 ]
	cg setshape "girl setshape "boy
	cg repeat 3 [ setshape "lion1 wait 10 setshape "lion2 wait 10 ]

Note so far we have been typing commands one line at a time into the command center now we will look at typing commands into a procedure.

A procedure is a list of commands typed into the procedures page. All procedures start with the word to and end with the word end. Note all procedures must have unique names. eg to circle.

To switch to the procedures page select Pages | Procedures
or use the keyboard shortcut CTRL + F

At first the procedures page will be blank

Copy a procedure from the example below or type your own.

; Note these comments are only to help explain the program.
; You don't have to type the comments for the program to work.

to circle              ; start of a procedure called circle
  repeat 360 [         ; repeats all commands within the square                          ; brackets [ ] n times
    fd 1               ; move forward one turtle step
    rt 1               ; right turn 1 degree
  ]                    ; end of repeat
end                    ; end of procedure

Close the procedures page by typing CTRL + F

Type the name of the procedure in the command center eg circle.

circle

The power of procedures comes from using one procedure again and again.

to circle
  pd
  repeat 180 [ fd 2 rt 2 ]
end

to torus
  cg
  repeat 36 [ circle rt 10 ] ; draw 36 circles each 10 degrees apart
end

Some shapes using procedures

	to circle           ; start of a procedure                       ; called circle   pd                ; pen down   repeat 360 [      ; repeats all commands                       ; within the square                       ;  brackets n times     fd 1            ; move forward one step     rt 1            ; right turn 1 degree   ]                 ; end of repeat end                 ; end of procedure
	to triangle         ; start of a procedure called                       ; triangle   pd                ; pen down   repeat 3 [        ; repeats all commands                       ; within the square                       ;  brackets n times     fd 200          ; move forward 200 turtle steps     rt 120          ; right turn 120 degree   ]                 ; end of repeat end                 ; end of procedure
	to square           ; start of a procedure called                       ; square   pd                ; pen down   repeat 4 [        ; repeats commands n times     fd 100          ; move forward 100 turtle steps     rt 90           ; right turn 90 degrees   ]                 ; end of repeat end                 ; end of procedure

	to octagon                     pd                     repeat 8 [        ; repeats all commands n times     fd 90           ; move forward 90 turtle steps     lt 360 / 8      ; left turn 360 divided by 8                       ; degrees   ]                     end
	to polygon   cg   pu   setpos [ 20 -60 ] ; move the turtle   pd   repeat sides [    ; repeats sides times     fd 800 / sides  ; move 800 / sides     lt 360 / sides  ; left turn 360 / sides degrees   ] end Note this procedure uses a slider named sides to change the number of sides in the polygon.

Use a button to run a procedure or type the name of the procedure in the command center.

Use sliders to change the value of a variable within a procedure.

To insert a slider 1 click on the slider tool 2 type the name of the slider ~ sides ~
3 enter the Minimum: and Maximum: vaues for the slider 4 click OK

APA citation:
Russell, R. (2016, July 04, 02:14 pm). Microworlds intro.
     Retrieved November 22, 2024, from http://www.rupert.id.au/microworlds/intro.php

Last refreshed: November 22 2024. 06:24.10 pm

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