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

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| Welcome to the spoken tutorial on Variables in '''Perl'''.  

| Welcome to the spoken tutorial on Variables in '''Perl'''.  

|-

|-

|  In this tutorial, we will learn about Variables in '''Perl'''

|  In this tutorial, we will learn about Variables in '''Perl'''

|-

|-

|  I am using '''Ubuntu Linux12.04''' operating system and  

|  I am using '''Ubuntu Linux12.04''' operating system and  

|-

|-

| '''Perl''' '''5.14.2 ''' that is, '''Perl''' revision 5 version 14 and subversion 2

| '''Perl''' '''5.14.2 ''' that is, '''Perl''' revision 5 version 14 and subversion 2

|-

|-

| I will also be using the '''gedit Text Editor'''.  

| I will also be using the '''gedit Text Editor'''.  

|-

|-

| You can use any text editor of your choice.

| You can use any text editor of your choice.

|-

|-

|  '''Variables''' in '''Perl''':

|  '''Variables''' in '''Perl''':

|-

|-

| '''Variables''' are used for storing values, like text strings, numbers or arrays.

| '''Variables''' are used for storing values, like text strings, numbers or arrays.

|-

|-

| 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.

|-

|-

|  '''Scalar''' represents a single value and can store '''scalars''' only.

|  '''Scalar''' represents a single value and can store '''scalars''' only.

|-

|-

| '''Scalar variables''' are declared using $ ('''dollar''') symbol.

| '''Scalar variables''' are declared using $ ('''dollar''') symbol.

|-

|-

|  Let us look at '''Variable Declaration''':

|  Let us look at '''Variable Declaration''':

|-

|-

| A '''variable''' can be declared as follows: '''dollar priority semicolon'''

| A '''variable''' can be declared as follows: '''dollar priority semicolon'''

|-

|-

| '''Variable''' names in '''Perl''' can have several formats. '''Variables''' must begin with a letter or '''underscore'''  

| '''Variable''' names in '''Perl''' can have several formats. '''Variables''' must begin with a letter or '''underscore'''  

|-

|-

|  And may contains letters, digits, '''underscores''' or a combination of above 3.

|  And may contains letters, digits, '''underscores''' or a combination of above 3.

|-

|-

|  '''Variables''' declared with CAPITAL letters have special meaning in '''Perl.'''  

|  '''Variables''' declared with CAPITAL letters have special meaning in '''Perl.'''  

|-

|-

| So avoid declaring '''variables''' using Capital letters.

| So avoid declaring '''variables''' using Capital letters.

|-

|-

|  Now open the '''Terminal''' and type  '''gedit variables dot pl ampersand '''

|  Now open the '''Terminal''' and type  '''gedit variables dot pl ampersand '''

|-

|-

| The '''ampersand''' will unlock the command prompt on the '''terminal'''. Now press '''Enter'''.

| The '''ampersand''' will unlock the command prompt on the '''terminal'''. Now press '''Enter'''.

|-

|-

|  This will open the '''variables.pl '''file in '''gedit''' text editor.

|  This will open the '''variables.pl '''file in '''gedit''' text editor.

|-

|-

| '''dot pl '''is the default extension of a '''Perl''' file.

| '''dot pl '''is the default extension of a '''Perl''' file.

|-

|-

|  Type the following in the file; '''dollar priority semicolon''' and press '''Enter'''.

|  Type the following in the file; '''dollar priority semicolon''' and press '''Enter'''.

|-

|-

|  So we have declared the '''variable priority'''.

|  So we have declared the '''variable priority'''.

|-

|-

| You do not need to declare a '''variable''' before using it;

| You do not need to declare a '''variable''' before using it;

|-

|-

| you can just use it into your code.  

| you can just use it into your code.  

|-

|-

|  Now let us assign a numerical value to the '''variable priority'''.  

|  Now let us assign a numerical value to the '''variable priority'''.  

|-

|-

| For this type '''dollar priority space equal to space one semicolon'''

| For this type '''dollar priority space equal to space one semicolon'''

|-

|-

| and press '''Enter'''.

| and press '''Enter'''.

|-

|-

|  Next, type

|  Next, type

|-

|-

| '''print space double quote Value of variable is: dollar priority slash n''' close double quote '''semicolon''' and press enter

| '''print space double quote Value of variable is: dollar priority slash n''' close double quote '''semicolon''' and press enter

|-

|-

| '''slash n''' is the new line character.

| '''slash n''' is the new line character.

|-

|-

|  Now save this file as '''variables.pl''' at any location.

|  Now save this file as '''variables.pl''' at any location.

|-

|-

| In my case, it will get saved in '''home/amol '''directory. Now save this file

| In my case, it will get saved in '''home/amol '''directory. Now save this file

|-

|-

|  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.

|-

|-

| To do so, on the '''Terminal''' type, '''chmod 755 variables dot pl'''

| To do so, on the '''Terminal''' type, '''chmod 755 variables dot pl'''

|-

|-

| This will provide read, write & execute rights to the file.

| This will provide read, write & execute rights to the file.

|-

|-

|  To compile this '''Perl''' script, on the '''Terminal'''

|  To compile this '''Perl''' script, on the '''Terminal'''

|-

|-

| type ;'''perl hyphen c variables dot pl'''

| type ;'''perl hyphen c variables dot pl'''

|-

|-

|  '''Hyphen c '''switch compiles the '''Perl''' script for any compilation/syntax error.

|  '''Hyphen c '''switch compiles the '''Perl''' script for any compilation/syntax error.

|-

|-

| Now press '''Enter'''

| Now press '''Enter'''

|-

|-

| This tells us that there is no syntax error in our script.

| This tells us that there is no syntax error in our script.

|-

|-

|  Now let's execute the '''Perl''' script by typing '''perl variables dot pl''' and press '''Enter'''.

|  Now let's execute the '''Perl''' script by typing '''perl variables dot pl''' and press '''Enter'''.

|-

|-

|  The output displayed is as highlighted.

|  The output displayed is as highlighted.

|-

|-

|  We can also assign a '''string''' value to the '''variable''' we declared.

|  We can also assign a '''string''' value to the '''variable''' we declared.

|-

|-

| Switch back to the Text editor window.

| Switch back to the Text editor window.

|-

|-

|  Instead of '''dollar priority equal to one;'''  type

|  Instead of '''dollar priority equal to one;'''  type

|-

|-

| '''dollar priority equal to in single quote high '''

| '''dollar priority equal to in single quote high '''

|-

|-

|  Please note that  the assignments are evaluated from right to left.

|  Please note that  the assignments are evaluated from right to left.

|-

|-

| A '''scalar''' can hold data of any type, be it a '''string''', a number  

| A '''scalar''' can hold data of any type, be it a '''string''', a number  

|-

|-

|  Save this file and compile the script once again by typing

|  Save this file and compile the script once again by typing

|-

|-

| '''perl hyphen c variables dot pl''' now press '''Enter'''.

| '''perl hyphen c variables dot pl''' now press '''Enter'''.

|-

|-

|  This tells us that there is no syntax error.

|  This tells us that there is no syntax error.

|-

|-

| Execute the script by typing '''perl variables dot pl''' and press '''Enter'''.

| Execute the script by typing '''perl variables dot pl''' and press '''Enter'''.

|-

|-

|  The output is as shown.

|  The output is as shown.

|-

|-

|  Now switch back to the Text Editor window.

|  Now switch back to the Text Editor window.

|-

|-

| You can also use '''scalars''' within a double-quoted '''strings''' as

| You can also use '''scalars''' within a double-quoted '''strings''' as

|-

|-

| '''dollar priority in double quote String'''

| '''dollar priority in double quote String'''

|-

|-

| Save this file and close it.

| Save this file and close it.

|-

|-

|  let us learn how to declare multiple '''variables'''.

|  let us learn how to declare multiple '''variables'''.

|-

|-

| To do so open the new file in Text Editor.

| To do so open the new file in Text Editor.

|-

|-

|  on'''Terminal''' type - '''gedit multivar dot pl space ampersand''' and press '''Enter'''.

|  on'''Terminal''' type - '''gedit multivar dot pl space ampersand''' and press '''Enter'''.

|-

|-

| This will open '''multivar dot pl''' file in text editor

| This will open '''multivar dot pl''' file in text editor

|-

|-

|  Now  type -

|  Now  type -

|-

|-

| '''dollar firstVar comma dollar secondVar semicolon''' and press '''Enter'''.

| '''dollar firstVar comma dollar secondVar semicolon''' and press '''Enter'''.

|-

|-

|  To copy the value of variable '''dollar firstVar''' to '''dollar secondVar''', type -

|  To copy the value of variable '''dollar firstVar''' to '''dollar secondVar''', type -

|-

|-

| '''dollar firstVar space equal to space dollar secondVar semicolon''' and press '''Enter'''.

| '''dollar firstVar space equal to space dollar secondVar semicolon''' and press '''Enter'''.

|-

|-

|  All mathematical operations like addition, subtraction, multiplication, division, can be done on these variables  

|  All mathematical operations like addition, subtraction, multiplication, division, can be done on these variables  

|-

|-

| Let us see how we can achieve this using '''Perl'''.

| Let us see how we can achieve this using '''Perl'''.

|-

|-

|  Switch to text editor.

|  Switch to text editor.

|-

|-

| And now let us assign the value '''10''' to both of these variables by typing,  

| And now let us assign the value '''10''' to both of these variables by typing,  

|-

|-

| '''dollar firstVar equal to dollar secondVar equal to ten semicolon''' And Press '''Enter'''.

| '''dollar firstVar equal to dollar secondVar equal to ten semicolon''' And Press '''Enter'''.

|-

|-

|  Now to print these values, type

|  Now to print these values, type

|-

|-

| '''print double quote firstVar: dollar firstVar and secondVar: dollar secondVar slash n''' close double quote  '''semicolon''' press '''Enter'''.

| '''print double quote firstVar: dollar firstVar and secondVar: dollar secondVar slash n''' close double quote  '''semicolon''' press '''Enter'''.

|-

|-

| Now save this file.

| Now save this file.

|-

|-

|  Now let us add the values in the two variables.

|  Now let us add the values in the two variables.

|-

|-

| For this type

| For this type

|-

|-

| '''dollar addition space equal to space dollar firstVar plus space dollar secondVar semicolon'''and Press '''Enter'''.

| '''dollar addition space equal to space dollar firstVar plus space dollar secondVar semicolon'''and Press '''Enter'''.

|-

|-

|  Notice, we haven't declared the variable '''addition'''.

|  Notice, we haven't declared the variable '''addition'''.

|-

|-

|  Once again, to print the value of the  variable  '''addition''', type

|  Once again, to print the value of the  variable  '''addition''', type

|-

|-

| '''print double quote Addition is dollar addition slash n''' close  double quote  '''semicolon'''

| '''print double quote Addition is dollar addition slash n''' close  double quote  '''semicolon'''

|-

|-

| Save this file

| Save this file

|-

|-

|  To compile this file again on terminal type

|  To compile this file again on terminal type

|-

|-

| '''perl hyphen c multivar dot pl'''

| '''perl hyphen c multivar dot pl'''

|-

|-

| There is no syntax error so we can execute the script...

| There is no syntax error so we can execute the script...

|-

|-

|  by typing '''perl multivar dot pl'''

|  by typing '''perl multivar dot pl'''

|-

|-

|  This will produce an output as highlighted.

|  This will produce an output as highlighted.

    

    

|-

|-

|  Similarly, try subtraction, multiplication and division.

|  Similarly, try subtraction, multiplication and division.

|-

|-

| I have written the code here.

| I have written the code here.

|-

|-

|  Now let us save this file and close it.

|  Now let us save this file and close it.

|-

|-

|  Now compile the file by typing

|  Now compile the file by typing

|-

|-

| '''perl hyphen c multivar dot pl'''

| '''perl hyphen c multivar dot pl'''

|-

|-

| There is no syntax error.

| There is no syntax error.

|-

|-

| So we can execute the script as '''perl multivar dot pl'''

| So we can execute the script as '''perl multivar dot pl'''

|-

|-

| On execution the output will look like this.

| On execution the output will look like this.

|-

|-

|  This brings us to the end of this tutorial.

|  This brings us to the end of this tutorial.

|-

|-

| In this tutorial we have learnt,  

| In this tutorial we have learnt,  

|-

|-

| To Declare and Use '''scalar variables''' in '''Perl'''

| To Declare and Use '''scalar variables''' in '''Perl'''

|-

|-

|  '''Assignment'''

|  '''Assignment'''

|-

|-

|  Declare a number '''variable'''.  

|  Declare a number '''variable'''.  

|-

|-

| Assign  10 to it.  

| Assign  10 to it.  

|-

|-

|  Print the '''variable''' declared.

|  Print the '''variable''' declared.

|-

|-

| Declare 2 '''string variables'''.

| Declare 2 '''string variables'''.

|-

|-

|  Assign these values to them - “Namaste ” and “India”.  

|  Assign these values to them - “Namaste ” and “India”.  

|-

|-

|  Print those '''2  variables''' one after the other.

|  Print those '''2  variables''' one after the other.

|-

|-

|  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 tutorial dot org  

| For more details, please write to  contact at spoken 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 following link.

|  More information on this Mission is available  at the following link.

|-

|-

|  Hope you enjoyed this '''Perl''' tutorial. This is Amol Brahmankar signing off.

|  Hope you enjoyed this '''Perl''' tutorial. This is Amol Brahmankar signing off.

|-

|-

|  Thanks for joining.

|  Thanks for joining.

|}

|}