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. Please note that all build in commands we discuss here are highlighted with dark green in the code editor, this can help you to distinguish them.

Moving the turtle

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

forward (fw)

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 (bw)

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 (tl)

turnleft

turnleft X

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

turnright (tr)

turnright

turnright X

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

direction (dir)

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

center moves the turtle to the center on the canvas.

go

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

gox X

gox using this command the turtle will move to X pixels from the left of the canvas whilst staying at the same height.

goy

goy

goy Y

gox using this command the turtle will move to Y pixels from the top of the canvas whilst staying at 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 (pu)

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 (pd)

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 (pw)

penwidth

penwidth X

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

pencolor (pc)

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 (cs)

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 is the new height of the canvas in pixels. canvassize can be abbreviated to cs.

canvascolor (cc)

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

wrapon

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

wrapoff

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 wrapping is.

Commands to clean up

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

clear (cr)

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 cr.

reset

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 turtle is positioned at the middle of the screen, the canvas color is white, and the turtle draws a black line on the canvas.

The turtle is a sprite

First a brief explanation of what sprites are: sprites are small pictures that can be moved around the screen, like we often see in computer games. Our turtle is also a sprite. For more info see the glossary on sprites.

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 (ss)

show

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

hide (sh)

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?

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

print

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 = 2003
author = "Cies"
print author + " started the KTurtle project in " + year + " and still enjoys working on it!"

A command that rolls dice for you

There is one command that rolls dice for you, it is called random, and it is very useful for some unexpected results.

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.

Input and feedback though dialogs

A dialog is a small pop-up window that provides some feedback or asks for some input. KTurtle has two commands for dialogs, namely: message and inputwindow

message

message

message X

The message command takes a string as input. It shows a pop-up dialog containing the text from the string.

year = 2003
author = "Cies"
print author + " started the KTurtle project in " + year + " and still enjoys working on it!"

inputwindow

inputwindow

inputwindow X

inputwindow takes a string as input. It shows a pop-up dialog containing the text from the string, just like the message. But in addition to it also puts an input field on the dialog. Through this input filed the user can enter a number or a string which can be stored in a container. For example

in = inputwindow "What is you age?"
out = 2003 - in
print "In 2003 you where " + out + " years old at some point."

When a user cancels the input dialog, or does not enter anything at all the container is emptied.