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.
There are several commands to move the turtle over the screen.
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 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 X
turnleft
commands the turtle to turn an amount of X degrees to the left. turnleft
can be abbreviated to tl
.turnright X
turnright
the turtle to turn an amount of X degrees to the right. turnright
can be abbreviated to tr
.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
.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 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 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
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
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 X
penwidth
sets the width of the pen (the line width) to an amount of X pixels. penwidth
can be abbreviated to pw
.pencolor R,G,B
pencolor
sets the color of the pen. pencolor
takes an RGB combination as input. pencolor
can be abbreviated to pc
.There are several commands to control the canvas.
canvascolor R,G,B
canvascolor
set the color of the canvas. canvascolor
takes an RGB combination as input. canvascolor
can be abbreviated to cc
.There are two commands to clean up the canvas after you have made a mess.
clearWith
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
.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
makes the turtle visible again after it has been hidden. show
can be abbreviated to ss
.The answer is: “yes”. The turtle can write: it writes just about everything you command it to.
print XThe
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!"
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.There is one command that rolls dice for you, it is called random
, and it is very useful for some unexpected results.
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.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
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.
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