Chapter 4. KTurtle's Logo Programming Reference

Commands

Using commands you tell the turtle or KTurtle to do something. Some commands need input, some give output. In this section we explain all the commands that can be used in KTurtle.

Moving the turtle

There are several commands to move the turtle over the screen.

forward

forward X
forward moves the turtle forward by the amount of X pixels. When the pen is down the turtle will leave a trail. forward can be abbreviated to fw

backward

backward X
backward moves the turtle backward by the amount of X pixels. When the pen is down the turtle will leave a trail. backward can be abbreviated to bw.

turnleft

turnleft X
turnleft commands the turtle to turn an amount of X degrees to the left. turnleft can be abbreviated to tl.

turnright

turnright X
turnrightthe turtle to turn an amount of X degrees to the right. turnright can be abbreviated to tr.

direction

direction X
direction set the turtle's direction to an amount of X degrees counting from zero, and thus is not relative to the turtle's previous direction. direction can be abbreviated to dir.

center

center
center moves the turtle to the center on the canvas.

go

go X,Y
go commands the turtle to go to a certain place on the canvas. This place is X pixels from the left of the canvas, and Y pixels form the top of the canvas. Note that using the go command the turtle will not draw a line.

gox

gox X
gox using this command the turtle will move to X pixels from the left of the canvas while she keeps his height.

goy

goy Y
gox using this command the turtle will move to Y pixels from the top of the canvas while she keeps his on the same distance from the left border of the canvas.

The turtle has a pen

The turtle has a pen, that draws a line when the turtle moves. There are a few commands to control the pen. In this section we explain these commands.

penup

penup
penup lifts the pen from the canvas. When the pen is “up” no line will be drawn when the turtle moves.See also pendown.penup can be abbreviated to pu.

pendown

pendown
pendown presses the pen down on the canvas. When the pen is press “down” on the canvas a line will be drawn when the turtle moves. See also penup.pendown can be abbreviated to pd.

penwidth

penwidth X
penwidth sets the width of the pen (the ligne width) to an amount of X pixels.penwidth can be abbreviated to pw.

pencolor

pencolor R,G,B
pencolor sets the color of the pen. pencolor takes an RGB combination as input.pencolor can be abbreviated to pc.

Commands to control the canvas

There are several commands to control the canvas.

canvassize

canvassize X,Y
With the canvassize command you can set the size of the canvas. It takes X and Y as input, where X is the new canvas width in pixels, and Y id the new height of the canvas in pixels.canvassize can be abbreviated to cs.

canvascolor

canvascolor R,G,B
canvascolor set the color of the canvas. canvascolor takes an RGB combination as input.canvascolor can be abbreviated to cc.

wrapon

wrapon
With the wrapon command you can set wrapping “on” for the canvas. Please see the glossary if you want to know what is wrapping.

wrapoff

wrapoff
With the wrapoff command you can set wrapping “off” for the canvas. This means the turtle can move off the canvas and can get “lost”. Please see the glossary if you want to know what is wrapping.

Commands to clean up

There are two commands to clean up the canvas after you have made a mess.

clear

clear
With clear you can clean all drawings from the canvas. All other things remain: the position and angle of the turtle, the canvascolor, the visibility of the turtle and the canvas size.clear can be abbreviated to ccl.

reset

reset
reset cleans much more thoroughly than the clear command. After a reset command everything is like is was when you had just started KTurtle. The tortle is positionned at the middle of the screen, the canvas color is white and the turtle daws a black line on the canvas.

The turtle is a sprite

Many people do not know what sprites are, so here a short explanation: sprites are small pictures that can be moved around the screen. (for more info see the glossary on sprites). So the turtle is a sprite!

Next you will find a full overview on all commands to work with sprites.

[The current version of KTurtle does not yet support the use of sprites other than the turtle. With future versions you will be able to change the turtle into something of your own design!]

show

show
show makes the turtle visible again after she has been hidden.show can be abbreviated to ss.

hide

hide
hide hides the turtle. This can be used if the turtle does not fit in your drawing.hide can be abbreviated to sh.

Can the turtles write text?

The answer is: “yes”. The turtle can write, he writes just about everything you command him to.

print

print X
The print command is used to command the turtle to write something on the canvas. print takes numbers and strings as input. You can print various numbers and strings using the “+” symbol. See here a small example:
year = 2004
author = "Cies"
print "KTurtle was made in " + year + " by " + author

fontsize

fontsize X
fontsize sets the size of the font that is used by print. fontsize takes one input which should be a number. The size is set in pixels.

A command that rolls a dice for you

There is one command that rolls a dice for you

random

random X,Y
random is a command that takes input and gives output. As input are required two numbers, the first (X) sets the minimum output, the second (Y) sets the maximum. The output is a randomly chosen number that is equal or greater then the minimum and equal or smaller than the maximum. Here a small example:
repeat 500 [
  x = random 1,20
  forward x
  turnleft 10 - x
]
Using the random command you can add a bit of chaos to your program.