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

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|-
 
|-
 
|  00:02
 
|  00:02
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|   Welcome to the '''Spoken Tutorial''' on '''Variables in Ruby'''.  
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| Welcome to the '''Spoken Tutorial''' on '''Variables in Ruby'''.  
  
 
|-
 
|-
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|-
 
|-
 
|  00:09
 
|  00:09
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|* What is a variable?
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| What is a variable? Dynamic typing in '''Ruby'''
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+
−
|-
+
−
|  00:10
+
−
|* Dynamic typing in '''Ruby'''
+
  
 
|-
 
|-
 
|  00:13
 
|  00:13
−
|* Declaring a variable
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| Declaring a variable
  
 
|-
 
|-
 
|  00:15
 
|  00:15
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|* Converting variable types  
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| Converting variable types  
  
 
|-
 
|-
 
|  00:18   
 
|  00:18   
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|* What is variable's scope?
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| What is variable's scope?
  
 
|-
 
|-
 
|  00:20
 
|  00:20
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|* Types of variables.
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| Types of variables.
  
 
|-
 
|-
 
|  00:23
 
|  00:23
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|  Here, we are using:
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|  Here, we are using: '''Ubuntu Linux''' version '''12.04''', '''Ruby 1.9.3'''
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* '''Ubuntu Linux''' version '''12.04'''
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−
* '''Ruby 1.9.3'''
+
  
 
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|-
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|  00:38
 
|  00:38
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| You must also be familiar with '''irb'''.
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| You must also be familiar with '''"irb"'''.
  
 
|-
 
|-
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|-
 
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|  00:47
 
|  00:47
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|  Now I will explain what a '''variable''' is.
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|  Now, I will explain you what a '''variable''' is.
  
 
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|01:07  
 
|01:07  
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|  Variable name may only contain lowercase '''letters''', numbers, underscores.  Ex : first_name
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|  Variable name may only contain lowercase letters, numbers, underscores.  Ex : first_name
  
 
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|-
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|-
 
|-
 
|  01:27
 
|  01:27
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|  It means that you don't need to declare '''data type''' while creating a variable.
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|  It means that you don't need to declare datatype while creating a variable.
  
 
|-
 
|-
 
|  01:34
 
|  01:34
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|  '''Ruby interpreter '''determines the data type at the time of assignment.
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|  '''Ruby interpreter '''determines the datatype at the time of assignment.
  
 
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|-
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|-
 
|  01:51  
 
|  01:51  
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| A terminal window appears on your screen.
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| A '''terminal window''' appears on your screen.
  
 
|-
 
|-
 
| 01:55
 
| 01:55
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|  Now, type "irb".
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|  Now, type "irb" and
  
 
|-
 
|-
 
|  01:57
 
|  01:57
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| Press '''Enter '''to launch '''Interactive Ruby'''.
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| press '''Enter '''to launch '''Interactive Ruby'''.
  
 
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|  02:37
 
|  02:37
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|  We will get the output as: "true".
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|  We get the output as "true".
  
 
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|-
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|  02:53
 
|  02:53
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|   Type: '''var1''' equal to within double quotes '''hello'''and   press '''Enter'''.
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| Type: '''var1''' equal to within double quotes '''hello''' and press '''Enter'''.
  
 
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|  03:20
 
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|  We get the output as "string".
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|  We get the output as "String".
  
 
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|  03:35
 
|  03:35
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| Let's switch back to slides.
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| Let's switch back to slide.
  
 
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|  03:38  
 
|  03:38  
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| Ruby '''variable classe'''s have methods to convert their value to a different type.
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| Ruby variable classes have methods to convert their value to a different type.
  
 
|-
 
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|  03:45
 
|  03:45
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|  ''''to_i''''method is used to convert a variable to '''integer'''.
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|  ''''to_i'''' method is used to convert a variable to '''integer'''.
  
 
|-
 
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|  03:51
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|  ''''to_f''''method is used to convert a variable to '''floating point value'''.
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|  ''''to_f'''' method is used to convert a variable to '''floating point value'''.
  
 
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|  ''''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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|  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.  
  
 
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|  04:55
 
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| We will get the value as '''float'''.
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| We get the value as '''float'''.
  
 
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| 05:06
 
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|  We will get output 20, within double quotes.
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|  We get the output as 20, within double quotes.
  
 
|-
 
|-
 
|  05:10
 
|  05:10
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| To convert variable 'y' in binary form, give number base as '''2''' in '''to_s''' method.
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| To convert variable 'y' in binary form, give '''number base''' as '''2''' in the '''to_s''' method.
  
 
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|  05:18
 
|  05:18
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| Press up-arrow key to get the previous command.  
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| Press the up-arrow key to get the previous command.  
  
 
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|  05:44
 
|  05:44
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|  Let us switch back to our slide.
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|  Let us switch back to our '''slide'''.
  
 
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|  05:51
 
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| '''Scope''' defines where in a program, a variable is accessible.
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| '''Scope''' defines- where in a program, a variable is accessible.
  
 
|-
 
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|  05:56
 
|  05:56
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| '''Ruby''' has four types of variable scope:
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| '''Ruby''' has four types of variable scopes:
  
 
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|  06:00
 
|  06:00
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|* Local
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| Local, Global  
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+
−
|-
+
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| 06:01
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−
|* Global  
+
  
 
|-
 
|-
 
|  06:02
 
|  06:02
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|* Instance and
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|Instance and  
  
 
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|-
 
|  06:04
 
|  06:04
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|* Class.
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| Class.
  
 
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|-
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|-
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|   06:14
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| 06:14
 
| '$' represents '''global''' variable.  
 
| '$' represents '''global''' variable.  
  
 
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| 06:18  
 
| 06:18  
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| Lower case letters and underscore represents a '''local''' variable.
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| Lower case letters and underscore represent a '''local''' variable.
  
 
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| 06:37
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| We will learn in detail about this in another tutorial.
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| We will learn in detail, about this, in another tutorial.
  
 
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|  06:51
 
|  06:51
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|* To declare a variable, e.g. var1=10
+
|To declare a variable, e.g. var1=10
  
 
|-
 
|-
 
|  06:56
 
|  06:56
−
|*  Changing variable type using '''to_f, to_s method'''s
+
| Changing a variable type using 'to_f' and 'to_s' methods
  
 
|-
 
|-
 
|  07:04
 
|  07:04
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|*  Different variable '''scope'''s.
+
| Different variable '''scope'''s.
  
 
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|  07:27
 
|  07:27
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| * Conducts workshops using spoken tutorials.  
+
| Conducts workshops using spoken tutorials.  
  
 
|-
 
|-
 
|  07:30
 
|  07:30
−
| * Gives certificates to those who pass an online test.  
+
| Gives certificates to those who pass an online test.  
  
 
|-
 
|-
 
|  07:34
 
|  07:34
−
| For more details, please write to:
+
| For more details, please write to: contact @ spoken hyphen tutorial dot org.
−
contact at spoken hyphen tutorial dot org.
+
  
 
|-
 
|-

Latest revision as of 12:00, 10 March 2017

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? 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 you 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 datatype 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" and
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 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 hello and 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 slide.
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 get the value as float.
04:57 Now, type: y dot to underscore s and press Enter.
05:06 We get the output as 20, within double quotes.
05:10 To convert variable 'y' in binary form, give number base as 2 in the to_s method.
05:18 Press the 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 scopes:
06:00 Local, 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 represent 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 a variable type using 'to_f' and '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 @ 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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