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

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 data type 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 quotes 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	Let's 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. Let's 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 represent a class variable.
06:33	Upper case letters represent 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 summarize.
06:48	In this tutorial, we have learnt:
06:51	* To declare a variable, e.g. var1=10
06:56	* Changing variable type using to_f, to_s methods
07:04	* Different variable scopes.
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 summarizes 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