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Hello everybody.

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Welcome to this tutorial on Grammar of TurtleScript in KTurtle.

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In this tutorial, we will learn about

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Grammar of Turtle script  and  'if'-'else' condition

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To record this tutorial I am using,  Ubuntu Linux OS version. 12.04.  KTurtle version. 0.8.1 beta.

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We assume that you have basic working knowledge of KTurtle

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If not, for relevant tutorials, please visit our website.  http://spoken-tutorial.org

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Let's open a new KTurtle Application.

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Click on Dash home.

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In the Search bar, type KTurtle.

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Click on the KTurtle icon.

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We  can also open  KTurtle  using Terminal.

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Press CTRL+ALT+T simultaneously to open the Terminal.

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Type KTurtle  and press enter   to open the KTurtle Application.

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Let's first look at TurtleScript

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TurtleScript is a programming language

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It has different types of words and symbols used for various purposes

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It instructs Turtle what to do

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Grammar of TurtleScript in  KTurtle includes-

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Comments

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Commands

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Numbers

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Strings

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Variables and

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Boolean values

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Now we will see where to store numbers

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Numbers  can be stored in

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Mathematical operators

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Comparison operators and

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Variables

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I will zoom the program text for clear view.

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First  let's look at variables.

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Variables are words that start with  ‘$’ sign, for example $a.

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Variables are highlighted in purple color.

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Using the assignment, equal to (=), a variable is given its content.

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Variables can contain  numbers $a=100.

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strings $a=hello or

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boolean values that is true or false $a=true

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Variable keeps the content until program finishes execution or until it is reassigned to something else.

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For example, consider the code.

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Let us type,$a = 2004

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$b = 25

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print $a + $b

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Variable 'a' is assigned a  value  2004.

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Variable 'b' is assigned a value 25

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print command, commands Turtle to write something on the canvas.

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print  command, takes numbers and strings as input.

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print $a + $b  commands Turtle to add two values and display them on the canvas.

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Let's Run the code in slow speed.

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Value 2029 is displayed on the canvas

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Let us next see the Mathematical  Operators.

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Mathematical operators include,

 + (Addition) 



 - (Subtraction) 



 * (Multiplcation)  and



 / (Division)

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I will clear the current code from editor and type clear command and RUN to clean the canvas

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I already have a program in a text editor.

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I will Explain the code now

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“reset” command sets Turtle to its default position

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canvassize 200,200 fixes the width and height of the canvas to 200 pixels each.

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value 1+1 is assigned to the variable $add,

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Value 20-5 is assigned to variable $subtract,

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value 15 * 2 is be assigned to the variable $multiply.

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30/30 is assigned to the variable $divide.

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go 10,10 commands to Turtle to go 10 pixels left of canvas and 10 pixels from top of canvas

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print command displays the varible on the canvas

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I will copy the code from text editor and paste it into KTurtle editor.

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Pause the tutorial and type the program into KTurtle editor.

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Resume the tutorial after typing the program

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Let us click on Run button  to run the program

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Command which is getting executed is highlighted on the editor.

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Turtle displays the values on the canvas at the specified positions.

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Let us consider a simple example for using  comparison operator .

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I will clear the current code from editor and type clear command and RUN to clean the canvas

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I will  zoom the progrm text to have clear view

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Let's type

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$answer = 10 > 3

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print $answer

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Here 10 is compared to 3 with the ’greater than’ operator.

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The result of this comparison, the boolean value true is stored in the

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variable $answer and the value true is displayed on the canvas.

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Let's run the code now

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Turtle displays Boolean value true on the canvas.

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Now lets see how Strings work in this application –

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Strings can be put in variables like numbers

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Strings cannot be used in mathematical or comparison operators

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Strings are highlighted in red color

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KTurtle identifies a line in double quotes as a string

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I will clear the current code from editor.type clear command and Run to clean the canvas

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Now  I will explain about Boolean values.

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There are only two boolean values: true and false.

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For example  Let's type the code

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$answer = 7<5

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print $answer

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Boolean value false is assigned to variable $answer  because 7 is greater than 5

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Let's Run the code now

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Turtle diplays Boolean value false on the canvas.

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Let's next learn about “if-else” conditon.

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‘if’ condition is executed only if the boolean value evaluates ‘true’

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‘else’ condition is executed only if the ‘if’ condition is ‘false’ .

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I will clear the current code from editor.type clear command and Run to clean the canvas

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I already have a code in a text file.

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This code compares  numbers 4 , 5 and 6 and  displays the results accordingly on the canvas.

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I will copy the code from text editor and paste it into KTurtle editor.

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Pause the tutorial and type the program into your KTurtle editor.

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Resume the tutorial after typing the program

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Let's Run the code now

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the Turtle has compared the values 4 and 5.

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and has displayed the  result 4 is smaller than 6 on the canvas .

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With this we come to the end of this tutorial.

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Let's summarize.

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In this tutorial, we have learnt about

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Grammar of Turtle script  and

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‘if-else’ condition

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Now to the assignment part.

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Solve an equation using

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if - else condition

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Mathematical  and comparision  operators

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Display the results using  “print” and “go” commands.

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To solve the assignment

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Choose any four random numbers

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Multiply two sets of random numbers

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Compare the results using the comparison operators

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Display both the results

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Display greater result at the  center of the canvas

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You can choose any equation which you like.

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Watch the video available at this URL http://spoken-tutorial.org/What is a Spoken Tutorial

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It summarises the Spoken Tutorial project

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If you do not have good bandwidth, you can download and watch it

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The Spoken Tutorial Project Team&#160;:

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Conducts workshops using spoken tutorials

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Gives certificates to those who pass an online test

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For more details, please write to  contact@spoken-tutorial.org

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Spoken Tutorial Project is a part of the Talk to a Teacher project

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It is supported by the National Mission on Education through ICT, MHRD, Government of India

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More information on this Mission is available at this link http://spoken-tutorial.org/NMEICT-Intro ]

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The Script is contributed by ITfC Bangaluru.

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This is Madhuri Ganpathi from IIT Bombay  signing off Thank you for joining.