Ruby/C2/Variables-in-Ruby/English-timed

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Time Narration
00:02 Welcome to the Spoken Tutorial on Variables in Ruby
00:06 In this tutorial we will learn
00:09 What is a variable?
00:10 Dynamic typing in Ruby
00:13 Declaring a variable
00:15 Converting variable types
00:18 What is variable's scope?
00:20 Types of variables
00:23 Here we are using Ubuntu Linux version 12.04 Ruby 1.9.3
00:32 To follow this tutorial you must have the knowledge of using Terminal in Linux.
00:38 You must also be familiar with irb
00:41 If not, for relevant tutorials, please visit our website
00:47 Now I will explain what a variable is.
00:50 Variable is used to store a value.
00:54 Variable is a reference that can be assigned.
00:58 Please note that Ruby variables are case sensitive.
01:04 Variable names should be meaningful.
01:07 Variable name may only contain lowercase letters, numbers, underscores. Ex : first_name
01:20 Now let us see what is dynamic typing
01:23 Ruby is a dynamic typed language.
01:27 It means that you don't need to declare datatype while creating a variable.
01:34 Ruby interpreter determines the data type at the time of assignment.
01:39 Now let us see how to declare a variable in Ruby.
01:45 Open the terminal by pressing Ctrl, Alt and T keys simultaneously.
01:51 A terminal window appears on your screen.
01:55 Now, type irb
01:57 Press Enter to launch Interactive Ruby
02:02 Now type var1 equal to 10 and Press Enter
02:09 Here we have declared a variable var1 and assigned a value 10 to it.
02:15 Let's check whether the datatype allotted by the interpreter is integer or not.
02:21 So, type var1 dot kind_(underscore)of (?)question mark Integer and press Enter
02:37 We will get the output as true.
02:39 In Ruby you can dynamically change the variable type.
02:44 To do so, just assign a new value to it.
02:47 Let's do this by assigning a string value to variable var1.
02:53 Type var1 equal to within double quote helloand press Enter
03:02 Let's verify the variable type assigned
03:06 Type var1 dot class
03:12 Class method tells us what class of variable it is. Now Press Enter
03:20 We get the output as string
03:23 Ruby has automatically changed the variable type from integer to string
03:29 We will now learn how to convert a variable value to different type
03:35 Lets switch back to slides
03:38 Ruby variable classes have methods to convert their value to a different type
03:45 to_i method is used to convert a variable to integer
03:51 to_f method is used to convert a variable to floating point value
03:57 to_s method is used to convert a variable to string
04:03 to _s method takes number base as an argument.
04:08 The conversion depends on this number base.
04:12 Now let us try out these methods.
04:15 Go to the terminal Lets clear the terminal first
04:21 Press Ctrl L to clear the irb console
04:25 Now Type y equal to 20 and Press Enter
04:32 Here we have declared a variable called y and assigned a value 20 to it.
04:39 We will now convert y to a floating point value using to underscore f method
04:47 Type y dot to underscore f and Press Enter
04:55 We will get the value as float.
04:57 Now Type y dot to underscore s and Press Enter
05:06 We will get output 20 within double quotes
05:10 To convert variable y in binary form give number base as 2 in to_s method
05:18 Press up arrow key to get the previous command
05:22 Type opening bracket 2 closing bracket and press Enter
05:29 We get the output in the binary form
05:33 Similarly you can convert variable y to octal or hexadecimal form
05:39 By changing the number base to 8 or 16.
05:44 Let us switch back to our slide
05:47 We will now learn what is a variable scope.
05:51 Scope defines where in a program a variable is accessible.
05:56 Ruby has four types of variable scope:
06:00 Local
06:01 Global
06:02 Instance and
06:04 Class
06:06 Each variable type is declared by using a special character at the beginning of the variable name
06:14 $ represents global variable
06:18 Lower case letters and underscore represents a local variable
06:25 @ represents an instance variable
06:29 Two @@ symbols represents a class variable
06:33 Upper case letters represents a constant
06:37 We will learn in detail about this in another tutorial.
06:42 This brings us to the end of this Spoken Tutorial. Let us summarises
06:48 In this tutorial we have learnt
06:51 To declare a variable eg var1=10
06:56 Changing variable type using to_f, to_s methods
07:04 Different Variable scope
07:06 As an assignment
07:08 Declare a variable and convert it to octal and hexadecimal form
07:14 Watch the video available at the following link.
07:17 It summarises the Spoken Tutorial project.
07:20 If you do not have good bandwidth, you can download and watch it.
07:24 The Spoken Tutorial Project Team :
07:27 Conducts workshops using spoken tutorials
07:30 Gives certificates to those who pass an online test
07:34 For more details, please write to contact at spoken hyphen tutorial dot org
07:41 Spoken Tutorial Project is a part of the Talk to a Teacher project.
07:45 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
07:51 More information on this Mission is available at the below link
07:57 This is Afrin Pinjari from IIT Bombay, signing off.Thank you for watching.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14, Sneha