Difference between revisions of "PERL/C2/while-do-while-loops/English-timed"

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|Welcome to the spoken tutorial on '''while and do-while''' loops in '''Perl'''

|Welcome to the spoken tutorial on '''while and do-while''' loops in '''Perl'''

   

   

|-

|-

| In this tutorial, we will learn about;  

| In this tutorial, we will learn about;  

|-

|-

|'''while''' loop in '''Perl'''  

|'''while''' loop in '''Perl'''  

|-

|-

|'''do-while loop in Perl '''

|'''do-while loop in Perl '''

   

   

|-

|-

| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''

| I am using '''Ubuntu Linux12.04''' operating system and '''Perl 5.14.2'''

   

   

|-

|-

|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.

   

   

|-

|-

| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''

| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''

   

   

|-

|-

|Knowledge of '''for''' and '''foreach''' loops in '''Perl''' will be an added advantage.

|Knowledge of '''for''' and '''foreach''' loops in '''Perl''' will be an added advantage.

|-

|-

|Please go through the relevant spoken tutorials on the spoken tutorial website.  

|Please go through the relevant spoken tutorials on the spoken tutorial website.  

   

   

|-

|-

| '''while''' loop in '''Perl'''

| '''while''' loop in '''Perl'''

   

   

|-

|-

|The '''while''' loop executes a block of code while a condition is true.  

|The '''while''' loop executes a block of code while a condition is true.  

   

   

|-

|-

|The syntax of '''while''' loop is as follows -  

|The syntax of '''while''' loop is as follows -  

   

   

|-

|-

|'''while space''' open bracket '''condition''' close bracket  

|'''while space''' open bracket '''condition''' close bracket  

   

   

|-

|-

|Open curly bracket  

|Open curly bracket  

   

   

|-

|-

|Piece of code to be executed while the condition is true  

|Piece of code to be executed while the condition is true  

   

   

|-

|-

|| Close curly bracket  

|| Close curly bracket  

   

   

|-

|-

| So, what happens if the condition is not satisfied? Then, the '''while''' loop will exit, without executing the code within, even once.  

| So, what happens if the condition is not satisfied? Then, the '''while''' loop will exit, without executing the code within, even once.  

|-

|-

|Now let us look at an example of '''while''' loop.  

|Now let us look at an example of '''while''' loop.  

|-

|-

|Open the Terminal and type  

|Open the Terminal and type  

   

   

|-

|-

|'''gedit whileLoop dot pl space ampersand'''

|'''gedit whileLoop dot pl space ampersand'''

    

    

|-

|-

|and press '''Enter'''

|and press '''Enter'''

   

   

|-

|-

|This will open the '''whileLoop.pl''' file in '''gedit. '''

|This will open the '''whileLoop.pl''' file in '''gedit. '''

   

   

|-

|-

| Now Type the following code  

| Now Type the following code  

   

   

|-

|-

| '''hash exclamation mark slash u s r slash bin slash perl'''

| '''hash exclamation mark slash u s r slash bin slash perl'''

   

   

|-

|-

|Press '''Enter'''

|Press '''Enter'''

   

   

|-

|-

| '''dollar i''' is equal to zero semicolon

| '''dollar i''' is equal to zero semicolon

   

   

|-

|-

| Press '''Enter '''

| Press '''Enter '''

   

   

|-

|-

|'''while''' open bracket '''dollar i less than or equal to four''' close bracket space  

|'''while''' open bracket '''dollar i less than or equal to four''' close bracket space  

   

   

|-

|-

|Open curly bracket press '''Enter''' and type  

|Open curly bracket press '''Enter''' and type  

   

   

|-

|-

|'''print''' space double quote '''Value of i''' colon,  ''' dollar i slash n''' close double quote  semicolon

|'''print''' space double quote '''Value of i''' colon,  ''' dollar i slash n''' close double quote  semicolon

   

   

|-

|-

|Press '''Enter '''

|Press '''Enter '''

   

   

|-

|-

| '''dollar i plus plus semicolon'''

| '''dollar i plus plus semicolon'''

    

    

|-

|-

| press '''Enter'''  and  

| press '''Enter'''  and  

|-

|-

|Close the curly bracket  

|Close the curly bracket  

   

   

|-

|-

|Let me explain the '''while''' loop in detail.  

|Let me explain the '''while''' loop in detail.  

   

   

|-

|-

| We have initialized the variable '''i''' to 0.  

| We have initialized the variable '''i''' to 0.  

|-

|-

|Now we have specified the condition for '''while''' loop as '''$i'''  less than or equal to 4.  

|Now we have specified the condition for '''while''' loop as '''$i'''  less than or equal to 4.  

   

   

|-

|-

| If the '''condition''' is true, the code within the '''while''' loop will get executed.  

| If the '''condition''' is true, the code within the '''while''' loop will get executed.  

|-

|-

|This means, first time our '''while''' loop will ''' print 'Value of i: 0' ''' on the terminal.  

|This means, first time our '''while''' loop will ''' print 'Value of i: 0' ''' on the terminal.  

   

   

|-

|-

|Then the ''' $i++ ''' will increments the value of variable i by one.  

|Then the ''' $i++ ''' will increments the value of variable i by one.  

|-

|-

|  Now again, the loop condition ''' $i<=4''' will be evaluated.  

|  Now again, the loop condition ''' $i<=4''' will be evaluated.  

   

   

|-

|-

|And the loop will exit once the value of i becomes 5.  

|And the loop will exit once the value of i becomes 5.  

   

   

|-

|-

| In this case, '''while''' loop will get executed for '''i''' equal to 0, 1, 2, 3, 4.   

| In this case, '''while''' loop will get executed for '''i''' equal to 0, 1, 2, 3, 4.   

   

   

|-

|-

| Press ctrl+s to save the file.  

| Press ctrl+s to save the file.  

   

   

|-

|-

|Now, switch to the terminal.  

|Now, switch to the terminal.  

   

   

|-

|-

| Type the following to check for any compilation or syntax error -  

| Type the following to check for any compilation or syntax error -  

   

   

|-

|-

|'''perl hyphen c whileLoop dot pl'''

|'''perl hyphen c whileLoop dot pl'''

   

   

|-

|-

|  and press '''Enter.'''

|  and press '''Enter.'''

   

   

|-

|-

|The following line will be displayed on the terminal  

|The following line will be displayed on the terminal  

   

   

|-

|-

|'''whileLoop.pl syntax OK '''

|'''whileLoop.pl syntax OK '''

   

   

|-

|-

|As there is no compilation or syntax error, we will execute the '''Perl''' script by typing -  

|As there is no compilation or syntax error, we will execute the '''Perl''' script by typing -  

   

   

|-

|-

|''' perl whileLoop dot pl'''

|''' perl whileLoop dot pl'''

   

   

|-

|-

|and press '''Enter'''

|and press '''Enter'''

   

   

|-

|-

|The following output will be displayed on the terminal.  

|The following output will be displayed on the terminal.  

   

   

|-

|-

| Now, let us look at '''do-while loop'''

| Now, let us look at '''do-while loop'''

|-

|-

| The '''do...while''' statement will always execute the piece of code at-least once.  

| The '''do...while''' statement will always execute the piece of code at-least once.  

   

   

|-

|-

| It will then check the condition and repeat the loop while the condition is true.  

| It will then check the condition and repeat the loop while the condition is true.  

   

   

|-

|-

|The syntax for '''do-while ''' loop is as follows -  

|The syntax for '''do-while ''' loop is as follows -  

|-

|-

|  '''do''' space  

|  '''do''' space  

   

   

|-

|-

|open curly bracket  

|open curly bracket  

|-

|-

|Piece of code to be executed while the condition is true  

|Piece of code to be executed while the condition is true  

   

   

|-

|-

|close curly bracket then space  

|close curly bracket then space  

   

   

|-

|-

|'''while''' space within brackets '''condition''' and then semicolon  

|'''while''' space within brackets '''condition''' and then semicolon  

   

   

|-

|-

|Open the Terminal and type;  

|Open the Terminal and type;  

|-

|-

| '''gedit doWhileLoop dot pl space ampersand'''

| '''gedit doWhileLoop dot pl space ampersand'''

   

   

|-

|-

|  and then press '''Enter'''

|  and then press '''Enter'''

|-

|-

|  This will open  '''doWhileLoop.pl''' file in '''gedit.'''  

|  This will open  '''doWhileLoop.pl''' file in '''gedit.'''  

   

   

|-

|-

| Type the following piece of code -  

| Type the following piece of code -  

|-

|-

|'''hash exclamation mark slash u s r slash bin slash perl'''  Press '''Enter'''

|'''hash exclamation mark slash u s r slash bin slash perl'''  Press '''Enter'''

   

   

|-

|-

|'''dollar i equals to zero semicolon press enter'''

|'''dollar i equals to zero semicolon press enter'''

|-

|-

|'''do''' space  

|'''do''' space  

   

   

|-

|-

|open curly bracket enter type  

|open curly bracket enter type  

|-

|-

|'''print''' space double quote '''Value of i colon space dollar i slash n''' close double quote  semicolon  

|'''print''' space double quote '''Value of i colon space dollar i slash n''' close double quote  semicolon  

   

   

|-

|-

|Press '''Enter '''

|Press '''Enter '''

   

   

|-

|-

|'''dollar i plus plus semicolon'''

|'''dollar i plus plus semicolon'''

   

   

|-

|-

| press '''enter '''

| press '''enter '''

   

   

|-

|-

| close curly bracket  

| close curly bracket  

   

   

|-

|-

|space '''while space''' open bracket '''dollar i less than or equal to four '''

|space '''while space''' open bracket '''dollar i less than or equal to four '''

   

   

|-

|-

|  close bracket semicolon  

|  close bracket semicolon  

|-

|-

| Here is the detail explanation of a '''do-while''' loop.  

| Here is the detail explanation of a '''do-while''' loop.  

   

   

|-

|-

|  We have initialized the variable i to 0.  

|  We have initialized the variable i to 0.  

|-

|-

|First time, the '''do-while''' loop will print the output as ''' 'Value of i colon 0' ''' on the terminal without checking for condition

|First time, the '''do-while''' loop will print the output as ''' 'Value of i colon 0' ''' on the terminal without checking for condition

   

   

|-

|-

|''' $i++ ''' will increment the value of variable i by one each time loop gets executed.  

|''' $i++ ''' will increment the value of variable i by one each time loop gets executed.  

   

   

|-

|-

| Second time, the condition '''$i''' less than or equal to 4 will be checked.  

| Second time, the condition '''$i''' less than or equal to 4 will be checked.  

   

   

|-

|-

| If the condition is true, the loop will get executed again.  

| If the condition is true, the loop will get executed again.  

|-

|-

|In our case, second time the output displayed on terminal will be ''' 'Value of i colon 1' '''.

|In our case, second time the output displayed on terminal will be ''' 'Value of i colon 1' '''.

   

   

|-

|-

|  The loop will get executed till the condition becomes false that is when variable i becomes 5.  

|  The loop will get executed till the condition becomes false that is when variable i becomes 5.  

   

   

|-

|-

| Press '''ctrl+s''' to '''save''' the file.  

| Press '''ctrl+s''' to '''save''' the file.  

   

   

|-

|-

|Now, switch to terminal and type the following to check for any compilation or syntax error.  

|Now, switch to terminal and type the following to check for any compilation or syntax error.  

   

   

|-

|-

|'''perl hyphen c doWhileLoop dot pl'''

|'''perl hyphen c doWhileLoop dot pl'''

   

   

|-

|-

|  and press '''Enter.'''

|  and press '''Enter.'''

|-

|-

| The following line will be displayed on the terminal

| The following line will be displayed on the terminal

   

   

|-

|-

|  '''doWhileLoop.pl syntax OK '''

|  '''doWhileLoop.pl syntax OK '''

|-

|-

|As there are no compilation or syntax errors, we will now execute the '''Perl''' script.  

|As there are no compilation or syntax errors, we will now execute the '''Perl''' script.  

   

   

|-

|-

|Type '''perl doWhileLoop dot pl'''

|Type '''perl doWhileLoop dot pl'''

   

   

|-

|-

|and press '''Enter'''

|and press '''Enter'''

 

 

|-

|-

| The following output will be displayed on the terminal.  

| The following output will be displayed on the terminal.  

   

   

|-

|-

| Now, let us see the actual difference between '''while''' and '''do-while''' loops.  

| Now, let us see the actual difference between '''while''' and '''do-while''' loops.  

|-

|-

| Open the Terminal, type -  

| Open the Terminal, type -  

|-

|-

| '''gedit loop dot pl space ampersand'''

| '''gedit loop dot pl space ampersand'''

   

   

|-

|-

| and press '''Enter'''

| and press '''Enter'''

|-

|-

| This will open '''loop dot pl''' file in '''gedit. '''

| This will open '''loop dot pl''' file in '''gedit. '''

|-

|-

| Now type the piece of code shown.  

| Now type the piece of code shown.  

|-

|-

| We have declared a variable '''count''' and initialized it to zero  

| We have declared a variable '''count''' and initialized it to zero  

|-

|-

|In the '''while''' loop condition, we are checking if the variable '''count''' is greater than zero.  

|In the '''while''' loop condition, we are checking if the variable '''count''' is greater than zero.  

|-

|-

|The condition is not true. So, the '''while''' loop code will not be executed even once.  

|The condition is not true. So, the '''while''' loop code will not be executed even once.  

|-

|-

|In the '''do...while''' loop, we are first executing the code and then checking the condition.  

|In the '''do...while''' loop, we are first executing the code and then checking the condition.  

|-

|-

|So, the code will be executed at least once.  

|So, the code will be executed at least once.  

|-

|-

|Then the condition whether the variable '''count''' is greater than zero, is checked.  

|Then the condition whether the variable '''count''' is greater than zero, is checked.  

|-

|-

|The condition is not true. So the loop will exit.  

|The condition is not true. So the loop will exit.  

|-

|-

|Now, press '''ctrl+s''' to save the file.  

|Now, press '''ctrl+s''' to save the file.  

|-

|-

|Now, switch to terminal and type the following to check for any compilation or syntax errors  

|Now, switch to terminal and type the following to check for any compilation or syntax errors  

|-

|-

|'''perl hyphen c loop dot pl'''

|'''perl hyphen c loop dot pl'''

|-

|-

|and press '''Enter.'''

|and press '''Enter.'''

|-

|-

|The following line will be displayed on the terminal.  

|The following line will be displayed on the terminal.  

|-

|-

|'''loop dot pl syntax OK'''

|'''loop dot pl syntax OK'''

|-

|-

|As there are no compilation or syntax errors, let us execute the '''Perl''' script.  

|As there are no compilation or syntax errors, let us execute the '''Perl''' script.  

|-

|-

|By Typing '''perl loop dot pl'''

|By Typing '''perl loop dot pl'''

|-

|-

|and press '''Enter.'''

|and press '''Enter.'''

|-

|-

|The following output will be displayed on the terminal.  

|The following output will be displayed on the terminal.  

|-

|-

|'''I am in do-while loop'''

|'''I am in do-while loop'''

|-

|-

|Here we can see, there is no output message displaying ''' 'I am in while loop' '''

|Here we can see, there is no output message displaying ''' 'I am in while loop' '''

|-

|-

|This message was what we printed inside the while loop.  

|This message was what we printed inside the while loop.  

|-

|-

|This implies that,  

|This implies that,  

   

   

|-

|-

|'''do-while''' loop executes at-least once before evaluating the condition

|'''do-while''' loop executes at-least once before evaluating the condition

|-

|-

|whereas '''while''' loop does not get executed even once when the condition specified is false.  

|whereas '''while''' loop does not get executed even once when the condition specified is false.  

|-

|-

|I hope the difference is clear to you now.  

|I hope the difference is clear to you now.  

|-

|-

|That's all there is to '''while''' and '''do-while''' loops.  

|That's all there is to '''while''' and '''do-while''' loops.  

|-

|-

|Let us summarize.  

|Let us summarize.  

|-

|-

|In this tutorial, we have learnt -  

|In this tutorial, we have learnt -  

|-

|-

|'''while''' loop and '''do-while''' loop in '''Perl'''  

|'''while''' loop and '''do-while''' loop in '''Perl'''  

|-

|-

|using sample programs.  

|using sample programs.  

|-

|-

|Here is assignment for you -  

|Here is assignment for you -  

|-

|-

|Print ''' 'Hello Perl' '''

|Print ''' 'Hello Perl' '''

|-

|-

|till the count of variable reaches 10  

|till the count of variable reaches 10  

|-

|-

|by using '''while''' loop and '''do-while''' loops  

|by using '''while''' loop and '''do-while''' loops  

|-

|-

|Watch the video available at the following link  

|Watch the video available at the following link  

|-

|-

|It summaries the Spoken Tutorial project

|It summaries 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

    

    

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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.

   

   

|-

|-

|More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro

|More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro

   

   

|-

|-

|  Hope you enjoyed this Perl tutorial.  

|  Hope you enjoyed this Perl tutorial.  

   

   

|-

|-

|This is Amol Brahmankar signing off.

|This is Amol Brahmankar signing off.

   

   

|-

|-

|Thanks for joining.

|Thanks for joining.

   

   

|}

|}