Ruby/C2/Variables-in-Ruby/English

Title of script: Variables in Ruby

Author: Afrin pinjari

Keywords: to_s, to_i, video tutorial, local variable, global variable

Visual Clue	Narration
Slide 1	Welcome to the Spoken Tutorial on Variables in Ruby
Slide 2 Learning Objectives	In this tutorial we will learn What is a variable? Dynamic typing in Ruby Declaring a variable Converting variable types What is variable's scope? Types of variables
Slide 3 System Requirements	Here we are using Ubuntu Linux version 12.04 Ruby 1.9.3
Slide 4 Pre-requisites	To follow this tutorial you must have knowledge of using Terminal in Linux. You must also be familiar with irb If not, for relevant tutorials, please visit our website
Slide 5 Variables	Now I will explain what a variable is. Variable is used to store a value. Variable is a reference that can be assigned. Please note that Ruby variables are case sensitive.
Slide 6 Variables	* Variable names should be meaningful. Variable name may only contain lowercase letters, numbers and underscores. Ex : first_name
Slide 7 Dynamic Typing	Now let us see what is dynamic typing Ruby is a dynamic typed language. It means that you don't need to declare datatype while creating a variable. Ruby interpreter determines the data type at the time of assignment.
	Now let us see how to declare a variable in Ruby.
Press Ctrl+Alt+t Switch to the terminal	Open the terminal by pressing Ctrl,Alt and T keys simultaneously. A terminal window appears on your screen.
Type irb<<Press Enter	Type irb Press Enter to launch Interactive Ruby
Type var1=10 <<press Enter	Now type var1 equal to 10 Press Enter
Highlight var1 Highlight 10	Here we have declared a variable var1 and assigned a value 10 to it.
	Let's check whether the datatype allotted by the interpreter is integer or not .
Type var1.kind_of?Integer << press Enter	So, type var1 dot kind underscore of question mark Integer and press Enter
Highlight true	We will get the output as true.
	In Ruby you can dynamically change the variable type. To do so, just assign a new value to it. Let's do this by assigning a string value to variable var1.
Type var1=”hello”<< press Enter	Type var1 equal to within double quote hello press Enter
Type var1.class<< press Enter	Let's verify the variable type assigned Type var1 dot class
Highlight .class	Class method tells us what class of variable it is and Now Press Enter
Highlight string	We get the output as string
	Ruby has automatically changed the variable type from integer to string
Slide 7 Converting variable types Highlight to_s	We will now learn how to convert a variable value to different type Lets switch back to slides Ruby variable classes have methods to convert their value to a different type to_i method is used to convert a variable to integer to_f method is used to convert a variable to floating point value to_s method is used to convert a variable to string The to _ s() method takes number base as an argument. The conversion depends on this number base.
Press Ctrl+L	Now let us try out these methods. Go to the terminal Lets clear the terminal first Press Ctrl,l to clear the irb console
Type y=20<<press Enter	Now Type y equal to 20 and Press Enter
Highlight y and 20	Here we have declared a variable called y and assigned a value 20 to it. We will now convert y to a floating point value using to underscore f method
Type y.to_f<< press Enter	Type y dot to underscore f and Press Enter
Highlight 20.0	We will get the value as float.
Type y.to_s<< press Enter	Now Type y dot to underscore s.and Press Enter
Highlight “20”	We will get output 20 within double quotes
	To convert variable y in binary form give number base as 2 in to_s method
Press Up Arrow	Press up arrow key to get the previous command
Type y.to_s(2)<<press Enter	Now type opening bracket 2 closing bracket and press Enter
Highlight 10100	We will get the output 10100 in the binary form
	Similarly you can convert variable y to octal or hexadecimal form By changing the number base to 8 or 16.
	Let us switch back to our slide
Slide 8 Variable Scope	We will now learn what is variable scope. Scope defines where in a program a variable is accessible. Ruby has four types of variable scope: Local Global Instance Class
Slide 9 Naming Convention	Each variable type is declared by using a special character At the beginning of the variable name Name Beginning With Variable Scope $ A global variable [a-z] or _ A local variable @ An instance variable @@ A class variable [A-Z] A constant $ represents global variable Lower case letters and underscore represents a local variable @ represents an instance variable Two @@ represents a class variable Upper case letters represents a constant
	We will learn in detail about this in another tutorial.
	<<Pause>> This brings us to the end of this Spoken Tutorial.let us summarise
Slide 11 Summary	In this tutorial we have learnt To declare a variable eg var1=10 Changing variable type using to_f, to_s methods Different Variable scope
Slide 13 Assignment	As an assignment Declare a variable and convert it to octal and hexadecimal form
Slide 14 About the Spoken Tutorial Project	Watch the video available at the following link. It summarises the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
Slide 15	The Spoken Tutorial Project Team : Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
Slide 16 Acknowledgement	Spoken Tutorial Project is a part of the Talk to a Teacher project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro. This is Afrin Pinjari from IIT Bombay, signing off. Thank you for watching.

Contributors and Content Editors

Afrin, Nancyvarkey, Sneha