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

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| Welcome to the spoken tutorial on Variables in '''Perl'''.  
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| Welcome to the spoken tutorial on '''Variables''' in '''Perl'''.  
  
 
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|  In this tutorial, we will learn about Variables in '''Perl'''
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|  In this tutorial, we will learn about '''variables''' in '''Perl'''
  
 
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| '''Perl''' '''5.14.2 ''' that is, '''Perl''' revision 5 version 14 and subversion 2
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| '''Perl''' '''5.14.2 ''' that is: '''Perl''' revision 5, version 14, and subversion 2.
  
 
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| '''Variables''' are used for storing values, like text strings, numbers or arrays.
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| '''Variables''' are used for storing values like text strings, numbers or arrays.
  
 
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| Once a '''variable''' is declared, it can be used over and over again in the script.
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| Once a variable is declared, it can be used over and over again in the script.
  
 
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| '''Scalar variables''' are declared using $ ('''dollar''') symbol.
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| '''Scalar''' variables are declared using $ (dollar) symbol.
  
 
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| A '''variable''' can be declared as follows: '''dollar priority semicolon'''
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| A variable can be declared as follows: '''dollar priority semicolon'''
  
 
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| '''Variable''' names in '''Perl''' can have several formats. '''Variables''' must begin with a letter or '''underscore'''  
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| '''Variable''' names in '''Perl''' can have several formats. Variables must begin with a letter or '''underscore''' (_).
  
 
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|  And may contains letters, digits, '''underscores''' or a combination of above 3.
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|  And may contain letters, digits, '''underscores''' or a combination of above three.
  
 
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|  '''Variables''' declared with CAPITAL letters have special meaning in '''Perl.'''  
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|  Variables declared with CAPITAL letters have special meaning in '''Perl.'''  
  
 
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| So avoid declaring '''variables''' using Capital letters.
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| So, avoid declaring variables using capital letters.
  
 
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|  Now open the '''Terminal''' and type  '''gedit variables dot pl ampersand '''
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|  Now open the '''Terminal''' and type: '''gedit variables dot pl ampersand'''(&)
  
 
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| The '''ampersand''' will unlock the command prompt on the '''terminal'''. Now press '''Enter'''.
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| The '''ampersand''' will unlock the command prompt on the terminal. Now press '''Enter'''.
  
 
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| '''dot pl '''is the default extension of a '''Perl''' file.
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| '''dot pl''' (.pl) is the default extension of a '''Perl''' file.
  
 
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|  Type the following in the file; '''dollar priority semicolon''' and press '''Enter'''.
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|  Type the following in the file: '''dollar priority semicolon''' and press '''Enter'''.
  
 
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|  Now let us assign a numerical value to the '''variable priority'''.  
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|  Now let us assign a numerical value to the variable '''priority'''.  
  
 
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| For this type '''dollar priority space equal to space one semicolon'''
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| For this, type: '''dollar priority space equal to space one semicolon'''
  
 
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|  Next, type
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|  Next, type:
  
 
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| '''print space double quote Value of variable is: dollar priority slash n''' close double quote '''semicolon''' and press enter
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| '''print''' space double quote '''Value of variable is:''' dollar '''priority''' slash '''n''' close double quote semicolon and press '''Enter'''.
  
 
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| '''slash n''' is the new line character.
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| '''slash n''' is the "new line" character.
  
 
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| In my case, it will get saved in '''home/amol '''directory. Now save this file
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| In my case, it will get saved in '''home/amol '''directory. Now save this file.
  
 
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|  Now, let us change the permissions of '''variables.pl''' file, which we just now created.
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|  Now, let us change the permissions of '''variables.pl''' file which we just now created.
  
 
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| This will provide read, write & execute rights to the file.
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| This will provide "read", "write" & "execute" rights to the file.
  
 
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|  To compile this '''Perl''' script, on the '''Terminal'''
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|  To compile this '''Perl''' script, on the '''Terminal''',
  
 
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| type ;'''perl hyphen c variables dot pl'''
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| type: '''perl hyphen c variables dot pl'''
  
 
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Revision as of 11:41, 7 May 2015

Time Narration
00:01 Welcome to the spoken tutorial on Variables in Perl.
00:06 In this tutorial, we will learn about variables in Perl
00:12 I am using Ubuntu Linux12.04 operating system and
00:18 Perl 5.14.2 that is: Perl revision 5, version 14, and subversion 2.
00:26 I will also be using the gedit Text Editor.
00:30 You can use any text editor of your choice.
00:34 Variables in Perl:
00:37 Variables are used for storing values like text strings, numbers or arrays.
00:44 Once a variable is declared, it can be used over and over again in the script.
00:50 Scalar represents a single value and can store scalars only.
00:56 Scalar variables are declared using $ (dollar) symbol.
01:00 Let us look at Variable Declaration:
01:03 A variable can be declared as follows: dollar priority semicolon
01:09 Variable names in Perl can have several formats. Variables must begin with a letter or underscore (_).
01:18 And may contain letters, digits, underscores or a combination of above three.
01:24 Variables declared with CAPITAL letters have special meaning in Perl.
01:30 So, avoid declaring variables using capital letters.
01:34 Now open the Terminal and type: gedit variables dot pl ampersand(&)
01:44 The ampersand will unlock the command prompt on the terminal. Now press Enter.
01:50 This will open the variables.pl file in gedit text editor.
01:56 dot pl (.pl) is the default extension of a Perl file.
02:01 Type the following in the file: dollar priority semicolon and press Enter.
02:10 So we have declared the variable priority.
02:13 You do not need to declare a variable before using it;
02:18 you can just use it into your code.
02:21 Now let us assign a numerical value to the variable priority.
02:25 For this, type: dollar priority space equal to space one semicolon
02:32 and press Enter.
02:34 Next, type:
02:36 print space double quote Value of variable is: dollar priority slash n close double quote semicolon and press Enter.
02:50 slash n is the "new line" character.
02:53 Now save this file as variables.pl at any location.
03:02 In my case, it will get saved in home/amol directory. Now save this file.
03:10 Now, let us change the permissions of variables.pl file which we just now created.
03:18 To do so, on the Terminal type, chmod 755 variables dot pl
03:27 This will provide "read", "write" & "execute" rights to the file.
03:32 To compile this Perl script, on the Terminal,
03:36 type: perl hyphen c variables dot pl
03:42 Hyphen c switch compiles the Perl script for any compilation/syntax error.
03:49 Now press Enter
03:51 This tells us that there is no syntax error in our script.
03:56 Now let's execute the Perl script by typing perl variables dot pl and press Enter.
04:06 The output displayed is as highlighted.
04:10 We can also assign a string value to the variable we declared.
04:15 Switch back to the Text editor window.
04:18 Instead of dollar priority equal to one; type
04:22 dollar priority equal to in single quote high
04:28 Please note that the assignments are evaluated from right to left.
04:34 A scalar can hold data of any type, be it a string, a number
04:38 Save this file and compile the script once again by typing
04:45 perl hyphen c variables dot pl now press Enter.
04:51 This tells us that there is no syntax error.
04:55 Execute the script by typing perl variables dot pl and press Enter.
05:03 The output is as shown.
05:07 Now switch back to the Text Editor window.
05:10 You can also use scalars within a double-quoted strings as
05:15 dollar priority in double quote String
05:19 Save this file and close it.
05:22 let us learn how to declare multiple variables.
05:27 To do so open the new file in Text Editor.
05:31 onTerminal type - gedit multivar dot pl space ampersand and press Enter.
05:42 This will open multivar dot pl file in text editor
05:48 Now type -
05:50 dollar firstVar comma dollar secondVar semicolon and press Enter.
06:00 To copy the value of variable dollar firstVar to dollar secondVar, type -
06:07 dollar firstVar space equal to space dollar secondVar semicolon and press Enter.
06:19 All mathematical operations like addition, subtraction, multiplication, division, can be done on these variables
06:30 Let us see how we can achieve this using Perl.
06:34 Switch to text editor.
06:36 And now let us assign the value 10 to both of these variables by typing,
06:41 dollar firstVar equal to dollar secondVar equal to ten semicolon And Press Enter.
06:51 Now to print these values, type
06:55 print double quote firstVar: dollar firstVar and secondVar: dollar secondVar slash n close double quote semicolon press Enter.
07:17 Now save this file.
07:19 Now let us add the values in the two variables.
07:23 For this type
07:25 dollar addition space equal to space dollar firstVar plus space dollar secondVar semicolonand Press Enter.
07:43 Notice, we haven't declared the variable addition.
07:47 Once again, to print the value of the variable addition, type
07:53 print double quote Addition is dollar addition slash n close double quote semicolon
08:05 Save this file
08:07 To compile this file again on terminal type
08:12 perl hyphen c multivar dot pl
08:18 There is no syntax error so we can execute the script...
08:24 by typing perl multivar dot pl
08:30 This will produce an output as highlighted.
08:34 Similarly, try subtraction, multiplication and division.
08:38 I have written the code here.
08:41 Now let us save this file and close it.
08:46 Now compile the file by typing
08:48 perl hyphen c multivar dot pl
08:54 There is no syntax error.
08:55 So we can execute the script as perl multivar dot pl
09:01 On execution the output will look like this.
09:06 This brings us to the end of this tutorial.
09:11 In this tutorial we have learnt,
09:14 To Declare and Use scalar variables in Perl
09:18 Assignment
09:20 Declare a number variable.
09:22 Assign 10 to it.
09:24 Print the variable declared.
09:26 Declare 2 string variables.
09:29 Assign these values to them - “Namaste ” and “India”.
09:34 Print those 2 variables one after the other.
09:38 Watch the video available at the following link
09:42 It summarises the Spoken Tutorial project
09:45 If you do not have good bandwidth, you can download and watch it
09:50 The Spoken Tutorial Project Team
09:53 Conducts workshops using spoken tutorials
09:56 Gives certificates to those who pass an online test
10:01 For more details, please write to contact at spoken tutorial dot org
10:08 Spoken Tutorial Project is a part of the Talk to a Teacher project
10:13 It is supported by the National Mission on Education through ICT, MHRD, Government of India
10:23 More information on this Mission is available at the following link.
10:29 Hope you enjoyed this Perl tutorial. This is Amol Brahmankar signing off.
10:34 Thanks for joining.

Contributors and Content Editors

Gaurav, Madhurig, PoojaMoolya, Sandhya.np14, Sneha

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