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

{| border=1

{| border=1

|| '''Narration'''

|| '''Narration'''

|-

|-

|  Welcome to the Spoken Tutorial on Variables in '''Ruby'''  

|  Welcome to the Spoken Tutorial on Variables in '''Ruby'''  

|-

|-

| In this tutorial we will learn

| In this tutorial we will learn

|-

|-

| What is a variable?

| What is a variable?

|-

|-

|  Dynamic typing in '''Ruby'''

|  Dynamic typing in '''Ruby'''

|-

|-

|  Declaring a variable

|  Declaring a variable

|-

|-

|  Converting variable types  

|  Converting variable types  

|-

|-

|  What is variable's scope?

|  What is variable's scope?

|-

|-

|  Types of variables

|  Types of variables

|-

|-

|  Here we are using  '''Ubuntu Linux version 12.04'''    '''Ruby''' 1.9.3

|  Here we are using  '''Ubuntu Linux version 12.04'''    '''Ruby''' 1.9.3

|-

|-

|  To follow this tutorial you must have the knowledge of using''' Terminal''' in '''Linux.'''

|  To follow this tutorial you must have the knowledge of using''' Terminal''' in '''Linux.'''

|-

|-

| You must also be familiar with '''irb'''

| You must also be familiar with '''irb'''

|-

|-

| If not, for relevant tutorials, please visit our website

| If not, for relevant tutorials, please visit our website

|-

|-

|  Now I will explain what a variable is.

|  Now I will explain what a variable is.

|-

|-

|  Variable is used to store a value.

|  Variable is used to store a value.

|-

|-

|  Variable is a reference that can be assigned.

|  Variable is a reference that can be assigned.

|-

|-

|  Please note that '''Ruby '''variables are''' case sensitive.'''

|  Please note that '''Ruby '''variables are''' case sensitive.'''

|-

|-

|  Variable names should be meaningful.  

|  Variable names should be meaningful.  

|-

|-

|  Variable name may only contain lowercase letters, numbers, underscores.  Ex : first_name

|  Variable name may only contain lowercase letters, numbers, underscores.  Ex : first_name

|-

|-

|  Now let us see what is dynamic typing

|  Now let us see what is dynamic typing

|-

|-

|  '''Ruby''' is a dynamic typed language.

|  '''Ruby''' is a dynamic typed language.

|-

|-

|  It means that you don't need to declare '''datatype''' while creating a variable.

|  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.

|  '''Ruby interpreter '''determines the data type at the time of assignment.

|-

|-

|  Now let us see how to declare a variable in '''Ruby.'''

|  Now let us see how to declare a variable in '''Ruby.'''

|-

|-

|  Open the terminal by pressing '''Ctrl, Alt''' and''' T '''keys simultaneously.

|  Open the terminal by pressing '''Ctrl, Alt''' and''' T '''keys simultaneously.

|-

|-

| A terminal window appears on your screen.

| A terminal window appears on your screen.

|-

|-

|  Now, type '''irb'''

|  Now, type '''irb'''

|-

|-

| Press '''Enter '''to launch '''Interactive Ruby'''

| Press '''Enter '''to launch '''Interactive Ruby'''

|-

|-

|  Now type '''var1''' equal to 10  and Press '''Enter'''

|  Now type '''var1''' equal to 10  and Press '''Enter'''

|-

|-

|  Here we have declared a variable '''var1''' and assigned a value '''10 ''' to it.

|  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.

|  Let's check whether the datatype allotted by the interpreter is  integer or not.

|-

|-

|  So, type '''var1'''  dot  '''kind'''_(underscore)'''of '''(?)question mark '''Integer''' and press '''Enter'''

|  So, type '''var1'''  dot  '''kind'''_(underscore)'''of '''(?)question mark '''Integer''' and press '''Enter'''

|-

|-

|  We will get the output as '''true.'''

|  We will get the output as '''true.'''

|-

|-

|  In''' Ruby''' you can dynamically change the variable type.

|  In''' Ruby''' you can dynamically change the variable type.

|-

|-

| To do so, just assign a new value to it.

| To do so, just assign a new value to it.

|-

|-

| Let's do this by assigning a '''string''' value to variable '''var1.'''

| Let's do this by assigning a '''string''' value to variable '''var1.'''

|-

|-

|  Type '''var1''' equal to within double quote '''hello'''and  press Enter

|  Type '''var1''' equal to within double quote '''hello'''and  press Enter

|-

|-

| Let's verify the variable type assigned  

| Let's verify the variable type assigned  

|-

|-

| Type  '''var1''' dot '''class '''

| Type  '''var1''' dot '''class '''

|-

|-

| Class method tells us what class of variable it is. Now  Press''' Enter'''

| Class method tells us what class of variable it is. Now  Press''' Enter'''

|-

|-

|  We get the output as '''string'''

|  We get the output as '''string'''

|-

|-

|  '''Ruby '''has automatically changed the variable type from '''integer''' to '''string'''

|  '''Ruby '''has automatically changed the variable type from '''integer''' to '''string'''

|-

|-

|  We will now learn how to convert a variable value to different type  

|  We will now learn how to convert a variable value to different type  

|-

|-

| Lets switch back to slides

| Lets switch back to slides

|-

|-

| '''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

|-

|-

|  '''to_i '''method is used to convert a variable to '''integer'''

|  '''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_f '''method is used to convert a variable to '''floating point value'''

|-

|-

|  '''to_s''' method is used to convert a variable to''' string'''  

|  '''to_s''' method is used to convert a variable to''' string'''  

|-

|-

|  '''to _s''' method takes number base as an argument.

|  '''to _s''' method takes number base as an argument.

|-

|-

| The conversion depends on this number base.  

| The conversion depends on this number base.  

|-

|-

|  Now let us try out these methods.

|  Now let us try out these methods.

|-

|-

| Go to the''' terminal'''  Lets clear the terminal first

| Go to the''' terminal'''  Lets clear the terminal first

|-

|-

| Press Ctrl L to clear the '''irb '''console  

| Press Ctrl L to clear the '''irb '''console  

|-

|-

| Now  Type '''y '''equal to '''20'''  and Press '''Enter'''

| Now  Type '''y '''equal to '''20'''  and Press '''Enter'''

|-

|-

|  Here we have declared a variable called''' y''' and assigned a value '''20''' to it.

|  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

| We will now convert '''y''' to a floating point value using '''to '''underscore''' f''' method

|-

|-

|  Type '''y '''dot '''to '''underscore '''f''' and  Press '''Enter'''

|  Type '''y '''dot '''to '''underscore '''f''' and  Press '''Enter'''

|-

|-

| We will get the value as float'''.'''

| We will get the value as float'''.'''

|-

|-

|  Now Type  '''y dot '''to '''underscore s''' and Press '''Enter'''

|  Now Type  '''y dot '''to '''underscore s''' and Press '''Enter'''

|-

|-

|  We will get output '''20 '''within double quotes

|  We will get output '''20 '''within double quotes

|-

|-

| 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

|-

|-

| Press up arrow key to get the previous command  

| Press up arrow key to get the previous command  

|-

|-

|  Type opening bracket 2 closing bracket and  press '''Enter'''

|  Type opening bracket 2 closing bracket and  press '''Enter'''

|-

|-

| We  get the output in the binary form

| We  get the output in the binary form

|-

|-

|  Similarly you can convert variable '''y''' to '''octal''' or '''hexadecimal''' form  

|  Similarly you can convert variable '''y''' to '''octal''' or '''hexadecimal''' form  

|-

|-

| By changing the number base to 8 or 16.

| By changing the number base to 8 or 16.

|-

|-

|  Let us switch back to our slide

|  Let us switch back to our slide

|-

|-

|  We will now learn what is a '''variable scope'''.

|  We will now learn what is a '''variable scope'''.

|-

|-

| '''Scope''' defines where in a program a variable is accessible.

| '''Scope''' defines where in a program a variable is accessible.

|-

|-

| '''Ruby''' has four types of variable scope:

| '''Ruby''' has four types of variable scope:

|-

|-

| Local

| Local

|-

|-

|Global  

|Global  

|-

|-

| Instance and

| Instance and

|-

|-

| Class

| Class

|-

|-

|  Each variable type is declared by using a special character at the beginning of the variable name  

|  Each variable type is declared by using a special character at the beginning of the variable name  

|-

|-

| '''$ '''represents ''' global''' variable  

| '''$ '''represents ''' global''' variable  

|-

|-

| Lower case letters and  underscore represents a '''local''' variable

| Lower case letters and  underscore represents a '''local''' variable

|-

|-

| '''@''' represents an '''instance''' variable  

| '''@''' represents an '''instance''' variable  

|-

|-

| Two''' @@''' symbols represents a '''class''' variable  

| Two''' @@''' symbols represents a '''class''' variable  

|-

|-

| Upper case letters represents a '''constant'''

| Upper case letters represents a '''constant'''

|-

|-

| We will learn in detail about this in another tutorial.

| We will learn in detail about this in another tutorial.

|-

|-

|  This brings us to the end of this Spoken Tutorial. Let us summarises

|  This brings us to the end of this Spoken Tutorial. Let us summarises

|-

|-

| In this tutorial we have learnt

| In this tutorial we have learnt

|-

|-

|  To declare a variable  eg var1=10

|  To declare a variable  eg var1=10

|-

|-

|  Changing variable type using to_f, to_s methods

|  Changing variable type using to_f, to_s methods

|-

|-

|  Different Variable '''scope'''

|  Different Variable '''scope'''

|-

|-

| As an assignment

| As an assignment

|-

|-

| Declare a variable and convert it to '''octal''' and '''hexadecimal''' form

| Declare a variable and convert it to '''octal''' and '''hexadecimal''' form

|-

|-

|  Watch the video available at the following link.

|  Watch the video available at the following link.

|-

|-

| It summarises the Spoken Tutorial project.

| It summarises the Spoken Tutorial project.

|-

|-

| If you do not have good bandwidth, you can download and watch it.  

| If you do not have good bandwidth, you can download and watch it.  

|-

|-

|  The Spoken Tutorial Project Team :

|  The Spoken Tutorial Project Team :

|-

|-

| Conducts workshops using spoken tutorials  

| Conducts workshops using spoken tutorials  

|-

|-

| Gives certificates to those who pass an online test  

| Gives certificates to those who pass an online test  

|-

|-

| For more details, please write to contact at spoken hyphen tutorial dot org

| For more details, please write to contact at spoken hyphen tutorial dot org

|-

|-

|  Spoken Tutorial Project is a part of the Talk to a Teacher project.

|  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.

| It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|-

|-

| More information on this Mission is available at the below link

| More information on this Mission is available at the below link

|-

|-

| This is Afrin Pinjari from IIT Bombay, signing off.

| This is Afrin Pinjari from IIT Bombay, signing off.