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

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!  <center>'''Visual Cue'''</center>
 
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|  In this tutorial, we will learn about Variables in '''Perl'''
 
|  In this tutorial, we will learn about Variables in '''Perl'''
  
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| You can use any text editor of your choice.
 
| You can use any text editor of your choice.
  
 
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|  '''Variables''' in '''Perl''':
 
|  '''Variables''' in '''Perl''':
  
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| Once a '''variable''' is declared, it can be used over and over again in the script.
 
| Once a '''variable''' is declared, it can be used over and over again in the script.
  
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| For this type '''dollar priority space equal to space one semicolon'''
 
| For this type '''dollar priority space equal to space one semicolon'''
  
 
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| and press '''Enter'''.
 
| and press '''Enter'''.
  
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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.
 
|  Now, let us change the permissions of '''variables.pl'''  file, which we just now created.
  
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|  To compile this '''Perl''' script, on the '''Terminal'''
 
|  To compile this '''Perl''' script, on the '''Terminal'''
  
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|  Save this file and compile the script once again by typing
 
|  Save this file and compile the script once again by typing
  
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|  The output is as shown.
 
|  The output is as shown.
  
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| Save this file and close it.
 
| Save this file and close it.
  
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| This will open '''multivar dot pl''' file in text editor
 
| This will open '''multivar dot pl''' file in text editor
  
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| '''dollar firstVar space equal to space dollar secondVar semicolon''' and press '''Enter'''.
 
| '''dollar firstVar space equal to space dollar secondVar semicolon''' and press '''Enter'''.
  
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| And now let us assign the value '''10''' to both these variables by typing,  
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| And now let us assign the value '''10''' to both of these variables by typing,  
  
 
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|  Now to print these values, type
  
 
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| I have written the code here.
 
| I have written the code here.
  
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| On execution the output will look like this.
 
| On execution the output will look like this.
  
 
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|  This brings us to the end of this tutorial.
 
|  This brings us to the end of this tutorial.
  
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|  Print the '''variable''' declared.
 
|  Print the '''variable''' declared.
 
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| Declare 2 '''string variables'''.
 
| Declare 2 '''string variables'''.
 
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| 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  
  
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| Gives certificates to those who pass an online  test  
 
| Gives certificates to those who pass an online  test  
  
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|  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  
  
 
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|  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  
  

Revision as of 11:25, 12 May 2014

Visual Cue
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 contains letters, digits, underscores or a combination of above 3.
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 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 double quote complete 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 double quote complete 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 double quote complete 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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