Difference between revisions of "Ruby/C2/Variables-in-Ruby/English-timed"

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|  Welcome to the Spoken Tutorial onVariables in '''Ruby'''  
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|  Welcome to the Spoken Tutorial on Variables in '''Ruby'''  
  
 
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|-
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|  00.07
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|  00.06
 
| In this tutorial we will learn
 
| In this tutorial we will learn
  
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|  00.09
 
|  00.09
 
| What is a variable?
 
| What is a variable?
 +
 
|-
 
|-
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|  00.11
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|  00.10
 
|  Dynamic typing in '''Ruby'''
 
|  Dynamic typing in '''Ruby'''
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|-
 
|-
 
|  00.13
 
|  00.13
 
|  Declaring a variable
 
|  Declaring a variable
 +
 
|-
 
|-
 
|  00.15
 
|  00.15
 
|  Converting variable types  
 
|  Converting variable types  
 +
 
|-
 
|-
 
|  00.18   
 
|  00.18   
 
|  What is variable's scope?
 
|  What is variable's scope?
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|-
 
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|  00.20
 
|  00.20
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|  00.23
 
|  00.23
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|  Here we are using  '''Ubuntu''' Linux version 12.04   '''Ruby''' 1.9.3
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|  Here we are using  '''Ubuntu Linux version 12.04'''    '''Ruby''' 1.9.3
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+
−
 
+
  
 
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|  00.32
 
|  00.32
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|  To follow this tutorial you must have knowledge of using''' Terminal''' in '''Linux.'''
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|  To follow this tutorial you must have the knowledge of using''' Terminal''' in '''Linux.'''
  
  
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|  00.41
 
|  00.41
 
| If not, for relevant tutorials, please visit our website
 
| If not, for relevant tutorials, please visit our website
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|  00.47
 
|  00.47
 
|  Now I will explain what a variable is.
 
|  Now I will explain what a variable is.
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|-
 
|-
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|  00.51
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|  00.50
 
|  Variable is used to store a value.
 
|  Variable is used to store a value.
 +
 
|-
 
|-
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|  00.55
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|  00.54
 
|  Variable is a reference that can be assigned.
 
|  Variable is a reference that can be assigned.
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|-
 
|-
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|  00.59
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|  00.58
 
|  Please note that '''Ruby '''variables are''' case sensitive.'''
 
|  Please note that '''Ruby '''variables are''' case sensitive.'''
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| 01.04
 
| 01.04
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|  Variable names should be '''meaningful'''.  
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|  Variable names should be meaningful.  
 +
 
 
|-
 
|-
 
|01.07  
 
|01.07  
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|  Variable name may only contain lowercase letters, numbers and underscores.  Ex : first_name
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|  Variable name may only contain lowercase letters, numbers, underscores.  Ex : first_name
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+
−
 
+
  
 
|-
 
|-
 
|  01.20
 
|  01.20
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|  Now''' '''let us see what is dynamic typing
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|  Now let us see what is dynamic typing
  
 
|-
 
|-
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|  01.24
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|  01.23
 
|  '''Ruby''' is a dynamic typed language.
 
|  '''Ruby''' is a dynamic typed language.
 
|-
 
|-
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|  01.28
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|  01.27
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|  It means that you '''don't''' need to declare '''datatype''' while creating a variable.
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|  It means that you don't need to declare '''datatype''' while creating a variable.
  
 
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|  01.45
 
|  01.45
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|  Open the terminal by pressing '''Ctrl,Alt''' and''' T '''keys simultaneously.
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|  Open the terminal by pressing '''Ctrl, Alt''' and''' T '''keys simultaneously.
  
  
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| 01.55
 
| 01.55
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|  Type''' ''''''irb'''
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|  Now, type '''irb'''
  
 
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|-
 
|  02.02
 
|  02.02
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|  Now type '''var1''' equal to '''10  and'''Press '''Enter'''
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|  Now type '''var1''' equal to 10  and Press '''Enter'''
  
 
|-
 
|-
 
|  02.09
 
|  02.09
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|  Here we have declared a variable '''var1''' and assigned a value '''10 '''to it'''.'''
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|  Here we have declared a variable '''var1''' and assigned a value '''10 ''' to it.
  
 
|-
 
|-
 
| 02.15
 
| 02.15
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|  Let's check whether the datatype allotted by the interpreter is  '''integer '''or not''' . '''
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|  Let's check whether the datatype allotted by the interpreter is  integer or not.
  
  
 
|-
 
|-
 
| 02.21
 
| 02.21
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|  So, type '''var1 '''dot '''kind''' underscore '''of '''question mark '''Integer'''and press '''Enter'''
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|  So, type '''var1''' dot '''kind'''_(underscore)'''of '''(?)question mark '''Integer''' and press '''Enter'''
  
 
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|  In''' Ruby''' you can dynamically change the variable type.
 
|  In''' Ruby''' you can dynamically change the variable type.
  
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| Let's do this by assigning a '''string''' value to variable '''var1.'''
 
| Let's do this by assigning a '''string''' value to variable '''var1.'''
  
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| 03.03  
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| 03.02  
 
| Let's verify the variable type assigned  
 
| Let's verify the variable type assigned  
  
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| 03.20
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| 03.23
 
|  '''Ruby '''has automatically changed the variable type from '''integer''' to '''string'''
 
|  '''Ruby '''has automatically changed the variable type from '''integer''' to '''string'''
  
 
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|  | We will now learn how to convert a variable value to different type  
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|  We will now learn how to convert a variable value to different type  
  
 
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| '''Ruby''' variable classes have methods to convert their value to a different type
 
| '''Ruby''' variable classes have methods to convert their value to a different type
  
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|  04.03
 
|  04.03
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| The '''to _''' '''s()''' method takes number base as an argument.
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| '''to _s''' method takes number base as an argument.
  
 
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|-
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|  04.21
 
|  04.21
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| Press Ctrl,l to clear the '''irb '''console  
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| Press Ctrl L to clear the '''irb '''console  
  
  
 
|-
 
|-
 
| 04.25
 
| 04.25
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| Now  Type '''y '''equal to '''20'''  and Press''' '''Enter
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| Now  Type '''y '''equal to '''20'''  and Press '''Enter'''
  
 
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|  04.40
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| We will now convert '''y''' to a floating point value using '''to '''underscore''' f''' method
 
| We will now convert '''y''' to a floating point value using '''to '''underscore''' f''' method
  
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|  Now Type  '''y '''dot '''to '''underscore '''s. and''' Press '''Enter'''
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|  Now Type  '''y dot '''to '''underscore s''' and Press '''Enter'''
  
 
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|  05.11
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| To convert variable '''y''' in binary form give number base as '''2''' in '''to_s''' method
 
| To convert variable '''y''' in binary form give number base as '''2''' in '''to_s''' method
  
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|  05.22
 
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|  Now type opening bracket 2 closing bracket and  press '''Enter'''
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|  Type opening bracket 2 closing bracket and  press '''Enter'''
  
 
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|-
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|  05.29
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| We will get the output''' 10100 '''in the binary form
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| We get the output in the binary form
  
 
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|  05.48
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|  05.47
 
|  We will now learn what is a '''variable scope'''.
 
|  We will now learn what is a '''variable scope'''.
  
  
 
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|  05.52
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|  05.51
 
| '''Scope''' defines where in a program a variable is accessible.
 
| '''Scope''' defines where in a program a variable is accessible.
  
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| '''Ruby''' has four types of variable scope:
 
| '''Ruby''' has four types of variable scope:
  
−
* '''Local'''
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|-
−
* '''Global'''
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|  06.00
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* '''Instance '''
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| Local
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* '''Class '''
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|-
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|  06.01
 +
|Global
  
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|  06.02
 +
| Instance and
  
 
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|  06.06
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|  06.04
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| Each variable type is declared by using a special character
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| Class
  
 
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|  06.11
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|  06.06
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| At the beginning of the variable name  
+
| Each variable type is declared by using a special character at the beginning of the variable name  
  
 +
  
 
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|    06.14
 
|    06.14
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| '''$ '''represents '''global''' variable  
+
| '''$ '''represents ''' global''' variable  
  
 
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|  06.29
 
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| Two''' @@''' represents a '''class''' variable  
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| Two''' @@''' symbols represents a '''class''' variable  
  
 
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| 06.48
 
| In this tutorial we have learnt
 
| In this tutorial we have learnt
  
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|  07.07
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|  07.06
 
| As an assignment
 
| As an assignment
  
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|  07.24
 
|  The Spoken Tutorial Project Team :
 
|  The Spoken Tutorial Project Team :
  
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|-
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|  07.46
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|  07.45
 
| It is supported by the National Mission on Education through ICT, MHRD, Government of India.
 
| It is supported by the National Mission on Education through ICT, MHRD, Government of India.
  
 
|-
 
|-
−
|  07.52
+
|  07.51
−
| More information on this Mission is available at:  spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
+
| More information on this Mission is available at the below link
  
 
|-
 
|-

Revision as of 14:48, 2 June 2014

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

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