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

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{| border=1
 
{| border=1
−
|| '''Time'''
+
!  <center>'''Visual Cue'''</center>
−
|| '''Narration'''
+
!  <center>'''Narration'''</center>
−
 
+
 +
|-
 +
| 00.01
 +
|Welcome to the spoken tutorial on '''while and do-while''' loops in '''Perl'''
 +
 
|-
 
|-
−
|00.01
+
| 00.06
−
||Welcome to the spoken tutorial on '''while and do-while '''loops in '''Perl'''
+
| In this tutorial, we will learn about;
  
 
|-
 
|-
−
| 00.07
+
|00.09
−
|In this tutorial, we will learn about;'''while '''loop in '''Perl'''
+
|'''while''' loop in '''Perl'''  
  
 
|-
 
|-
 
|00.11
 
|00.11
−
|'''do-while '''loop in '''Perl'''
+
|'''do-while loop in Perl '''
−
 
+
 
|-
 
|-
−
| 00.13
+
|00.12
−
|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'''
−
 
+
−
 
+
 
|-
 
|-
−
| 00.21
+
|00.20
−
|I will also be using the '''gedit '''Text Editor.
+
|I will also be using the '''gedit Text Editor'''.
−
 
+
−
 
+
 
|-
 
|-
−
| 00.25
+
|00.24
 
|You can use any text editor of your choice.
 
|You can use any text editor of your choice.
−
 
+
 
|-
 
|-
−
| 00.29
+
| 00.28
−
|You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl'''
+
| You should have basic knowledge of '''Variables '''and''' Comments '''in''' Perl.'''
−
 
+
−
 
+
 
|-
 
|-
−
| 00.33
+
|00.33
−
|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.
−
 
+
  
 
|-
 
|-
−
| 00.39
+
|00.38
−
|Please go through the relevant spoken tutorials on the '''spoken tutorial '''website.
+
|Please go through the relevant spoken tutorials on the spoken tutorial website.  
−
 
+
 
|-
 
|-
−
| 00.44
+
| 00.43
−
|'''while '''loop in '''Perl'''
+
| '''while''' loop in '''Perl'''
−
 
+
−
 
+
 
|-
 
|-
−
| 00.46
+
|00.45
−
|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.  
−
 
+
 
|-
 
|-
−
|  00.50
+
|00.50
−
|The syntax of '''while''' loop is as follows -
+
|The syntax of '''while''' loop is as follows -  
−
 
+
−
 
+
 
|-
 
|-
−
| 00.53
+
|00.53
−
|'''while space '''open bracket''' condition''' close bracket Open curly bracket  
+
|'''while space''' open bracket '''condition''' close bracket  
−
 
+
−
 
+
 
|-
 
|-
−
|01.00  
+
|00.58
−
|Piece of code to be executed while the condition is true. Close curly bracket
+
|Open curly bracket  
−
 
+
 +
 
|-
 
|-
−
|  01.07
+
|01.00
−
|  So, what happens if the condition is not satisfied? Then, the '''while''' loop will exit, without executing the code within, even once.
+
|Piece of code to be executed while the condition is true
−
 
+
 
|-
 
|-
−
| 01.17
+
|01.04
−
| Now let us look at an example of '''while''' loop.
+
|| Close curly bracket
−
 
+
 
|-
 
|-
−
|  01.20
+
| 01.07
−
|  Open the '''Terminal''' and type '''gedit whileLoop dot pl space ampersand'' and press''' Enter'''
+
| So, what happens if the condition is not satisfied? Then, the '''while''' loop will exit, without executing the code within, even once.
  
 
|-
 
|-
−
| 01.31
+
|01.16
−
|This will open the '''whileLoop'''.'''pl''' file in '''gedit'''.
+
|Now let us look at an example of '''while''' loop.  
−
 
+
  
 
|-
 
|-
−
| 01.35
+
|01.19
−
|Now Type the following code
+
|Open the Terminal and type
−
 
+
−
 
+
 +
|-
 +
|01.22
 +
|'''gedit whileLoop dot pl space ampersand'''
 +
 +
 +
|-
 +
|01.29
 +
|and press '''Enter'''
 +
 +
|-
 +
|01.31
 +
|This will open the '''whileLoop.pl''' file in '''gedit. '''
 +
 +
|-
 +
|01.34
 +
| Now Type the following code  
 +
 
|-
 
|-
 
| 01.37
 
| 01.37
−
|'''hash exclamation mark slash u s r slash bin slash perl''' Press '''Enter.'''
+
| '''hash exclamation mark slash u s r slash bin slash perl'''
−
 
+
−
 
+
 
|-
 
|-
−
| 01.47
+
|01.45
−
|'''dollar i''' is equal to zero '''semicolon'''
+
−
 
+
−
|-
+
−
|01.52
+
 
|Press '''Enter'''
 
|Press '''Enter'''
−
 
+
−
 
+
 
|-
 
|-
−
| 01.54
+
|01.47
−
|While''' open bracket dollar i less than or equal to four close bracket space
+
| '''dollar i''' is equal to zero semicolon
−
 
+
−
 
+
 
|-
 
|-
−
| 02.04
+
| 01.52
−
|Open curly bracket press enter and type
+
| Press '''Enter '''
−
 
+
−
 
+
 
|-
 
|-
−
| 02.08
+
|01.54
−
|'''print''' space double quote Value of i colon  dollar i '''slash n double '''quote complete '''semicolon'''
+
|'''while''' open bracket '''dollar i less than or equal to four''' close bracket space
−
 
+
 
|-
 
|-
−
| 02.21
+
|02.04
−
|Press '''Enter'''
+
|Open curly bracket press '''Enter''' and type
−
 
+
−
 
+
 
|-
 
|-
−
| 02.23
+
|02.08
−
|'''dollar i plus plus semicolon''' press enter and
+
|'''print''' space double quote '''Value of i''' colon,  ''' dollar i slash n''' doule quote complete semicolon
−
 
+
 
|-
 
|-
−
| 02.29
+
|02.20
−
|Close the curly bracket
+
|Press '''Enter '''
−
 
+
 
|-
 
|-
−
|  02.31
+
|02.22
−
| Let me explain the '''while''' loop in detail.
+
| '''dollar i plus plus semicolon'''
 +
 +
 
|-
 
|-
−
| 02.34
+
|02.27
−
|We have initialized the variable''' i''' to 0.
+
| press '''Enter''' and
  
 
|-
 
|-
−
| 02.39
+
|02.28
−
| Now we have specified the condition for '''while''' loop as '''$i '''less than or equal to 4.
+
|Close the curly bracket
  
 +
 
|-
 
|-
−
| 02.47
+
|02.31
−
|If the '''condition''' is true, the code within the '''while''' loop will get executed.
+
|Let me explain the '''while''' loop in detail.  
−
 
+
 
|-
 
|-
−
| 02.52
+
| 02.33
−
|  This means, first time our '''while''' loop will print ''''Value of i: 0' '''on the '''terminal'''.
+
| We have initialized the variable '''i''' to 0.  
  
 
|-
 
|-
−
| 03.01
+
|02.38
−
|  Then the '''$i++'''will increments the value of variable '''i '''by one.
+
|Now we have specified the condition for '''while''' loop as '''$i''' less than or equal to 4.  
−
 
+
 
|-
 
|-
−
|03.08
+
|02.46
−
| Now again, the loop condition '''$i<=4''' will be evaluated.
+
| If the '''condition''' is true, the code within the '''while''' loop will get executed.  
−
 
+
  
 +
 
|-
 
|-
−
| 03.17
+
|02.52
−
|And the loop will exit once the value of''' i''' becomes 5.
+
|This means, first time our '''while''' loop will ''' print 'Value of i: 0' ''' on the terminal.  
−
 
+
 +
 
|-
 
|-
−
|03.22
+
|03.01
−
| In this case, '''while''' loop will get executed for''' i''' equal to 0, 1, 2, 3, 4.
+
|Then the ''' $i++ ''' will increments the value of variable i by one.  
  
 
|-
 
|-
−
|03.32
+
| 03.08
−
|Press '''ctrl+s''' to '''save''' the file.
+
| Now again, the loop condition ''' $i<=4''' will be evaluated.
−
 
+
 +
|-
 +
|03.16
 +
|And the loop will exit once the value of i becomes 5.
 +
 +
|-
 +
|  03.22
 +
| In this case, '''while''' loop will get executed for '''i''' equal to 0, 1, 2, 3, 4. 
 +
 +
|-
 +
|  03.32
 +
| Press ctrl+s to save the file.  
 +
 +
 
|-
 
|-
 
|03.35
 
|03.35
−
|Now, switch to the '''terminal'''.
+
|Now, switch to the terminal.  
−
 
+
 
|-
 
|-
−
| 03.38
+
| 03.37
−
|  Type the following to check for any compilation or syntax error -
+
| Type the following to check for any compilation or syntax error -  
−
 
+
−
 
+
 
|-
 
|-
−
| 03.43
+
|03.42
−
|'''perl hyphen c whileLoop dot pl''' and press''' Enter.'''
+
|'''perl hyphen c whileLoop dot pl'''
−
 
+
 
|-
 
|-
−
|  03.49
+
| 03.47
−
| The following line will be displayed on the terminal  '''whileLoop.pl syntax OK'''
+
| and press '''Enter.'''
−
 
+
 
|-
 
|-
−
| 03.56
+
| 03.49
−
| As there is  no compilation or syntax error, we will execute the '''Perl''' script by typing -
+
|The following line will be displayed on the terminal
−
 
+
−
 
+
 
|-
 
|-
−
| 04.03
+
|03.52
−
|'''perl whileLoop dot pl''' and press '''Enter'''
+
|'''whileLoop.pl syntax OK '''
−
 
+
 
|-
 
|-
−
|   04.10
+
|03.56
−
| The following output will be displayed on the '''terminal'''.
+
|As there is no compilation or syntax error, we will execute the '''Perl''' script by typing -
−
 
+
 
|-
 
|-
−
| 04.15
+
| 04.02
−
|Now, let us look at '''do-while loop'''
+
|''' perl whileLoop dot pl'''
−
 
+
 
|-
 
|-
−
|  04.20
+
|04.06
−
| The '''do...while''' statement will always execute the piece of code at-least once.
+
|and press '''Enter'''
−
 
+
−
 
+
 
|-
 
|-
−
| 04.26
+
|04.09
−
|It will then check the '''condition''' and repeat the loop while the '''condition''' is true.
+
|The following output will be displayed on the terminal.  
−
 
+
 
|-
 
|-
−
| 04.31
+
| 04.14
−
| The syntax for '''do-while '''loop is as follows - '''do '''space
+
| Now, let us look at '''do-while loop'''
  
 
|-
 
|-
−
| 04.36
+
|   04.20
−
|open curly bracket
+
| The '''do...while''' statement will always execute the piece of code at-least once.
 +
 +
|-
 +
|  04.25
 +
| It will then check the condition and repeat the loop while the condition is true.
 +
 +
|-
 +
| 04.30
 +
|The syntax for '''do-while ''' loop is as follows -
  
 
|-
 
|-
−
| 04.38
+
| 04.34
−
|Piece of code to be executed while the '''condition''' is true
+
| '''do''' space
 +
 +
|-
 +
|04.36
 +
|open curly bracket
  
 
|-
 
|-
−
| 04.42
+
|04.38
−
|close curly bracket then space
+
|Piece of code to be executed while the condition is true
  
 +
 
|-
 
|-
−
| 04.45
+
|04.42
−
|'''while '''space within brackets '''condition''' and then '''semicolon'''
+
|close curly bracket then space
  
 +
 
|-
 
|-
−
| 04.51
+
|04.45
−
| Open the '''Terminal''' and type;
+
|'''while''' space within brackets '''condition''' and then semicolon
−
 
+
 +
|-
 +
|04.50
 +
|Open the Terminal and type;  
  
 
|-
 
|-
−
| 04.55
+
|04.54
−
|'''gedit doWhileLoop dot pl space ampersand'''
+
| '''gedit doWhileLoop dot pl space ampersand'''
−
 
+
−
 
+
 
|-
 
|-
 
| 05.03
 
| 05.03
−
|and then press''' Enter'''
+
| and then press '''Enter'''
  
 
|-
 
|-
 
| 05.05
 
| 05.05
−
| This will open the '''doWhileLoop'''.'''pl''' file in '''gedit'''.
+
| This will open the '''doWhileLoop.pl''' file in '''gedit.'''  
−
 
+
 
|-
 
|-
−
|  05.09
+
|05.09
−
|Type the following piece of code -
+
| Type the following piece of code -  
−
 
+
−
 
+
 
|-
 
|-
−
| 05.12
+
|05.11
−
|'''hash exclamation mark slash u s r slash bin slash perl'''
+
|'''hash exclamation mark slash u s r slash bin slash perl''' Press '''Enter'''
−
 
+
−
 
+
−
|-
+
−
| 05.20
+
−
|Press '''Enter'''
+
−
 
+
−
 
+
 
|-
 
|-
−
| 05.21
+
|05.21
 
|'''dollar i equals to zero semicolon press enter'''
 
|'''dollar i equals to zero semicolon press enter'''
  
 
|-
 
|-
−
| 05.28
+
|05.27
−
|'''do space'''
+
|'''do''' space
−
 
+
 
|-
 
|-
−
| 05.30
+
|05.29
−
| open curly bracket enter type
+
|open curly bracket enter type  
  
 
|-
 
|-
−
| 05.33
+
|05.33
−
|'''print space double''' quote''' Value of i colon space dollar i slash n''' double quote complete '''semicolon'''
+
|'''print''' space double quote '''Value of i colon space dollar i slash n''' double quote complete semicolon  
−
 
+
 
|-
 
|-
−
| 05.47
+
|05.46
−
|Press '''Enter'''
+
|Press '''Enter '''
−
 
+
−
 
+
 
|-
 
|-
−
| 05.49
+
|05.48
−
|'''dollar i plus plus semicolon''' '''press enter'''
+
|'''dollar i plus plus semicolon'''
−
 
+
 
|-
 
|-
−
| 05.54
+
| 05.52
−
|close curly bracket
+
| press '''enter '''
−
 
+
 
|-
 
|-
−
| 05.56
+
| 05.54
−
|space '''while space '''open bracket '''dollar i less than or equal to four '''
+
| close curly bracket  
−
 
+
 
|-
 
|-
−
| 06.06
+
|05.56
−
|close bracket '''semicolon'''
+
|space '''while space''' open bracket '''dollar i less than or equal to four '''
  
 +
 
|-
 
|-
−
|06.11
+
| 06.06
−
 | Here is the detail explanation of a '''do-while''' loop.
+
| close bracket semicolon
  
 
|-
 
|-
−
| 06.14
+
| 06.10
−
|We have initialized the variable''' i''' to 0.
+
| Here is the detail explanation of a '''do-while''' loop.  
−
 
+
 
|-
 
|-
−
|  06.19
+
| 06.13
−
|First time, the '''do-while''' loop will print the output as ''''Value of i colon 0'''' on the terminal
+
| We have initialized the variable i to 0.
−
 
+
  
 
|-
 
|-
−
| 06.26
+
| 06.18
−
|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
−
 
+
 
|-
 
|-
−
|  06.29
+
|06.28
−
|'''$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.  
−
 
+
 
|-
 
|-
−
| 06.37
+
| 06.36
−
| 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.  
−
 
+
−
 
+
 
|-
 
|-
−
| 06.44
+
| 06.43
−
|If the '''condition''' is true, the loop will get executed again.
+
| If the condition is true, the loop will get executed again.  
−
 
+
  
 
|-
 
|-
−
| 06.49
+
|06.48
−
|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' '''.
−
 
+
 
|-
 
|-
−
|  06.58
+
| 06.57
−
|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.  
−
 
+
 
|-
 
|-
−
|  07.07
+
| 07.05
−
| Press '''ctrl+s''' to '''save''' the file.
+
| Press '''ctrl+s''' to '''save''' the file.  
−
 
+
 
|-
 
|-
−
| 07.09
+
|07.09
−
|  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.  
−
 
+
−
 
+
 
|-
 
|-
−
| 07.16
+
|07.16
−
|'''perl hyphen c doWhileLoop dot pl''' and press''' Enter.'''
+
|'''perl hyphen c doWhileLoop dot pl'''
−
 
+
 
|-
 
|-
−
| 07.24
+
| 07.21
−
| The following line will be displayed on the '''terminal'''  
+
|   and press '''Enter.'''
  
 
|-
 
|-
−
| 07.27
+
| 07.23
−
|'''doWhileLoop.pl syntax OK'''
+
| The following line will be displayed on the terminal
−
 
+
 
|-
 
|-
−
| 07.31
+
| 07.26
−
|  As there are no compilation or syntax errors, we will now execute the '''Perl''' script.
+
| '''doWhileLoop.pl syntax OK '''
−
 
+
  
 
|-
 
|-
−
| 07.36 
+
|07.30
−
|Type,'''perl doWhileLoop dot pl''' and press '''Enter'''
+
|As there are no compilation or syntax errors, we will now execute the '''Perl''' script.
−
 
+
 
|-
 
|-
−
|  07.44
+
|07.36
−
|  The following output will be displayed on the '''terminal'''.
+
|Type '''perl doWhileLoop dot pl'''
−
 
+
 
|-
 
|-
−
|07.48  
+
|07.41
−
|Now, let us see the actual difference between '''while''' and '''do-while''' loops.
+
|and press '''Enter'''
 +
 +
|-
 +
| 07.43
 +
| The following output will be displayed on the terminal.
 +
   
 +
|-
 +
|07.48
 +
| Now, let us see the actual difference between '''while''' and '''do-while''' loops.  
  
 
|-
 
|-
−
|  07.53
+
|07.53
−
| Open the '''Terminal''' and type -
+
| Open the Terminal and type -  
−
 
+
  
 
|-
 
|-
−
| 07.56 
+
|07.55
−
|'''gedit loop dot pl space ampersand''' and press''' Enter'''
+
| '''gedit loop dot pl space ampersand'''
 +
 +
|-
 +
|08.01
 +
| and press '''Enter'''
  
 
|-
 
|-
−
| 08.03
+
|08.03
−
| This will open '''loop dot pl''' file in '''gedit'''.
+
| This will open '''loop dot pl''' file in '''gedit. '''
−
 
+
  
 
|-
 
|-
−
| 08.08
+
|08.07
−
|Now type the piece of code shown.
+
| Now type the piece of code shown.  
  
 
|-
 
|-
−
| 08.13
+
|08.12
−
| We have declared a variable '''count''' and initialized it to zero
+
| We have declared a variable '''count''' and initialized it to zero  
  
 
|-
 
|-
−
|  08.20
+
|08.19
−
| 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.  
−
 
+
  
 
|-
 
|-
−
| 08.30
+
|08.29
−
|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.  
  
 
|-
 
|-
−
| 08..36
+
|08.36
−
|Then  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.  
  
 
|-
 
|-
−
|  08.45
+
|08.44
−
| So, the code will be executed at least once.
+
|So, the code will be executed at least once.  
  
 
|-
 
|-
−
| 08.50
+
|08.49
−
| 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.  
  
 
|-
 
|-
 
|08.57
 
|08.57
−
|The '''condition''' is not true. So the loop will exit.
+
|The condition is not true. So the loop will exit.  
  
 
|-
 
|-
 
|09.02
 
|09.02
−
| Now, press '''ctrl+s''' to save the file.
+
|Now, press '''ctrl+s''' to save the file.  
  
 
|-
 
|-
−
|09.06
+
|09.05
−
|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  
  
 +
|-
 +
|09.12
 +
|'''perl hyphen c loop dot pl'''
  
 
|-
 
|-
−
| 09.13
+
|09.16
−
|'''perl hyphen c loop dot pl''' and press''' Enter.'''
+
|and press '''Enter.'''
  
 
|-
 
|-
 
|09.19
 
|09.19
−
|  The following line will be displayed on the terminal  '''loop dot pl syntax OK'''
+
|The following line will be displayed on the terminal.
  
 
|-
 
|-
−
| 09.27
+
|09.22
−
|  As there are no compilation or syntax errors, let us execute the '''Perl''' script.
+
|'''loop dot pl syntax OK'''
  
 
|-
 
|-
−
| 09.32
+
|09.26
−
|By Typing
+
|As there are no compilation or syntax errors, let us execute the '''Perl''' script.
−
 
+
  
 
|-
 
|-
−
| 09.34
+
|09.31
−
|'''perl loop dot pl''' and press '''Enter.'''
+
|By Typing '''perl loop dot pl'''
−
 
+
−
|-
+
−
|  09.39
+
−
|  The following output will be displayed on the terminal.
+
  
  
 
|-
 
|-
−
| 09.44
+
|09.36
−
|'''I am in do-while loop'''
+
|and press '''Enter.'''
  
 
|-
 
|-
−
|  09.47
+
|09.38
−
| Here we can see, there is no output message displaying ''''I am in while loop''''
+
|The following output will be displayed on the terminal.
−
 
+
  
 
|-
 
|-
−
| 09.52
+
|09.43
−
|This message was what we printed inside the '''while''' loop.
+
|'''I am in do-while loop'''
  
 
|-
 
|-
−
| 10.00
+
|09.46
−
|  This implies that,  
+
|Here we can see, there is no output message displaying ''' 'I am in while loop' '''
−
 
+
  
 
|-
 
|-
−
| 10.02
+
|09.52
−
|'''do-while''' loop executes at-least once before evaluating the '''condition'''
+
|This message was what we printed inside the while loop.
  
  
 
|-
 
|-
−
| 10.08
+
|09.59
−
|whereas '''while''' loop does not get executed even once when the '''condition''' specified is false.
+
|This implies that,
 +
 +
|-
 +
|10.01
 +
|'''do-while''' loop executes at-least once before evaluating the condition
  
 
|-
 
|-
−
| 10.16
+
|10.07
−
| I hope the difference is clear to you now.  
+
|whereas '''while''' loop does not get executed even once when the condition specified is false.  
−
 
+
  
 
|-
 
|-
−
| 10.19
+
|10.15
−
|That's all there is to '''while''' and '''do-while''' loops.
+
|I hope the difference is clear to you now.  
  
 
|-
 
|-
−
|  10.23
+
|10.18
−
|  Let us summarize.
+
|That's all there is to '''while''' and '''do-while''' loops.  
  
 
|-
 
|-
−
| 10.25
+
|10.22
−
|In this tutorial, we have learnt -
+
|Let us summarize.
  
 
|-
 
|-
−
| 10.27
+
|10.24
−
|'''while''' loop and '''do-while''' loop in '''Perl'''
+
|In this tutorial, we have learnt -  
 +
 
  
 
|-
 
|-
−
| 10.29
+
|10.26
−
|using sample programs.
+
|'''while''' loop and '''do-while''' loop in '''Perl'''
  
 
|-
 
|-
−
|10.32
+
|10.29
−
|Here is assignment for you -
+
|using sample programs.
  
 
|-
 
|-
−
|10.34
+
|10.31
−
|Print ''''Hello Perl''''  till the count of variable reaches 10
+
|Here is assignment for you -
  
 
|-
 
|-
−
|10.39
+
|10.33
−
|by using '''while''' loop and '''do-while''' loops
+
|Print ''' 'Hello Perl' '''
  
 
|-
 
|-
−
| 10.42
+
|10.35
−
| | Watch the video available at the following link
+
|till the count of variable reaches 10
  
  
 
|-
 
|-
−
|10.46
+
|10.38
−
|It summaries the Spoken Tutorial project
+
|by using '''while''' loop and '''do-while''' loops
  
 +
|-
 +
|10.41
 +
|Watch the video available at the following link
  
 +
|-
 +
|10.45
 +
|It summaries the Spoken Tutorial project
 +
 +
 
|-
 
|-
 
|10.49
 
|10.49
 
|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
−
 
+
 
|-
 
|-
−
| 10.54
+
| 10.53
−
|   The Spoken Tutorial Project Team  
+
| The Spoken Tutorial Project Team  
−
 
+
  
 
|-
 
|-
−
|10.57
+
| 10.56
−
|Conducts workshops using spoken tutorials
+
| Conducts workshops using spoken tutorials
−
 
+
  
 
|-
 
|-
 
|11.00
 
|11.00
 
|Gives certificates to those who pass an online  test
 
|Gives certificates to those who pass an online  test
−
 
+
−
 
+
 
|-
 
|-
 
|11.04
 
|11.04
 
|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
−
 
+
−
|-  
+
|-
−
| 11.12
+
| 11.12
−
|   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
−
 
+
−
 
+
 
|-
 
|-
 
|11.17
 
|11.17
 
|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.
−
 
+
−
 
+
 
|-
 
|-
−
|11.25
+
|11.24
−
|More information on this Mission is available spoken hypen tutorial dot org slash NMEICT hyphen Intro
+
|More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro
−
 
+
 
|-
 
|-
−
| 11.37
+
| 11.36
−
|  Hope you enjoyed this '''Perl''' tutorial.  
+
|  Hope you enjoyed this Perl tutorial.  
−
 
+
 +
|-
 +
|11.38
 +
|This is Amol Brahmankar signing off.
 +
 +
 
|-
 
|-
−
|11.39
+
|11.40
−
|This is Amol  signing off.Thanks for joining
+
|Thanks for joining.
 +
 +
|}

Revision as of 10:40, 6 May 2014

Visual Cue
Narration
00.01 Welcome to the spoken tutorial on while and do-while loops in Perl
00.06 In this tutorial, we will learn about;
00.09 while loop in Perl
00.11 do-while loop in Perl
00.12 I am using Ubuntu Linux12.04 operating system and Perl 5.14.2


00.20 I will also be using the gedit Text Editor.


00.24 You can use any text editor of your choice.
00.28 You should have basic knowledge of Variables and Comments in Perl.


00.33 Knowledge of for and foreach loops in Perl will be an added advantage.
00.38 Please go through the relevant spoken tutorials on the spoken tutorial website.
00.43 while loop in Perl
00.45 The while loop executes a block of code while a condition is true.
00.50 The syntax of while loop is as follows -
00.53 while space open bracket condition close bracket
00.58 Open curly bracket


01.00 Piece of code to be executed while the condition is true
01.04 Close curly bracket
01.07 So, what happens if the condition is not satisfied? Then, the while loop will exit, without executing the code within, even once.
01.16 Now let us look at an example of while loop.
01.19 Open the Terminal and type


01.22 gedit whileLoop dot pl space ampersand


01.29 and press Enter
01.31 This will open the whileLoop.pl file in gedit.
01.34 Now Type the following code
01.37 hash exclamation mark slash u s r slash bin slash perl
01.45 Press Enter
01.47 dollar i is equal to zero semicolon
01.52 Press Enter
01.54 while open bracket dollar i less than or equal to four close bracket space
02.04 Open curly bracket press Enter and type
02.08 print space double quote Value of i colon, dollar i slash n doule quote complete semicolon
02.20 Press Enter
02.22 dollar i plus plus semicolon


02.27 press Enter and
02.28 Close the curly bracket


02.31 Let me explain the while loop in detail.
02.33 We have initialized the variable i to 0.
02.38 Now we have specified the condition for while loop as $i less than or equal to 4.
02.46 If the condition is true, the code within the while loop will get executed.


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


03.01 Then the $i++ will increments the value of variable i by one.
03.08 Now again, the loop condition $i<=4 will be evaluated.
03.16 And the loop will exit once the value of i becomes 5.
03.22 In this case, while loop will get executed for i equal to 0, 1, 2, 3, 4.
03.32 Press ctrl+s to save the file.


03.35 Now, switch to the terminal.
03.37 Type the following to check for any compilation or syntax error -


03.42 perl hyphen c whileLoop dot pl
03.47 and press Enter.
03.49 The following line will be displayed on the terminal
03.52 whileLoop.pl syntax OK
03.56 As there is no compilation or syntax error, we will execute the Perl script by typing -
04.02 perl whileLoop dot pl
04.06 and press Enter


04.09 The following output will be displayed on the terminal.
04.14 Now, let us look at do-while loop
04.20 The do...while statement will always execute the piece of code at-least once.
04.25 It will then check the condition and repeat the loop while the condition is true.
04.30 The syntax for do-while loop is as follows -
04.34 do space
04.36 open curly bracket
04.38 Piece of code to be executed while the condition is true


04.42 close curly bracket then space


04.45 while space within brackets condition and then semicolon
04.50 Open the Terminal and type;
04.54 gedit doWhileLoop dot pl space ampersand
05.03 and then press Enter
05.05 This will open the doWhileLoop.pl file in gedit.
05.09 Type the following piece of code -
05.11 hash exclamation mark slash u s r slash bin slash perl Press Enter
05.21 dollar i equals to zero semicolon press enter
05.27 do space
05.29 open curly bracket enter type
05.33 print space double quote Value of i colon space dollar i slash n double quote complete semicolon
05.46 Press Enter
05.48 dollar i plus plus semicolon
05.52 press enter
05.54 close curly bracket
05.56 space while space open bracket dollar i less than or equal to four


06.06 close bracket semicolon
06.10 Here is the detail explanation of a do-while loop.
06.13 We have initialized the variable i to 0.
06.18 First time, the do-while loop will print the output as 'Value of i colon 0' on the terminal without checking for condition
06.28 $i++ will increment the value of variable i by one each time loop gets executed.
06.36 Second time, the condition $i less than or equal to 4 will be checked.
06.43 If the condition is true, the loop will get executed again.
06.48 In our case, second time the output displayed on terminal will be 'Value of i colon 1' .
06.57 The loop will get executed till the condition becomes false that is when variable i becomes 5.
07.05 Press ctrl+s to save the file.
07.09 Now, switch to terminal and type the following to check for any compilation or syntax error.
07.16 perl hyphen c doWhileLoop dot pl
07.21 and press Enter.
07.23 The following line will be displayed on the terminal
07.26 doWhileLoop.pl syntax OK
07.30 As there are no compilation or syntax errors, we will now execute the Perl script.
07.36 Type perl doWhileLoop dot pl
07.41 and press Enter
07.43 The following output will be displayed on the terminal.
07.48 Now, let us see the actual difference between while and do-while loops.
07.53 Open the Terminal and type -
07.55 gedit loop dot pl space ampersand
08.01 and press Enter
08.03 This will open loop dot pl file in gedit.
08.07 Now type the piece of code shown.
08.12 We have declared a variable count and initialized it to zero
08.19 In the while loop condition, we are checking if the variable count is greater than zero.
08.29 The condition is not true. So, the while loop code will not be executed even once.
08.36 In the do...while loop, we are first executing the code and then checking the condition.
08.44 So, the code will be executed at least once.
08.49 Then the condition whether the variable count is greater than zero, is checked.
08.57 The condition is not true. So the loop will exit.
09.02 Now, press ctrl+s to save the file.
09.05 Now, switch to terminal and type the following to check for any compilation or syntax errors
09.12 perl hyphen c loop dot pl
09.16 and press Enter.
09.19 The following line will be displayed on the terminal.
09.22 loop dot pl syntax OK
09.26 As there are no compilation or syntax errors, let us execute the Perl script.
09.31 By Typing perl loop dot pl


09.36 and press Enter.
09.38 The following output will be displayed on the terminal.
09.43 I am in do-while loop
09.46 Here we can see, there is no output message displaying 'I am in while loop'
09.52 This message was what we printed inside the while loop.


09.59 This implies that,
10.01 do-while loop executes at-least once before evaluating the condition
10.07 whereas while loop does not get executed even once when the condition specified is false.
10.15 I hope the difference is clear to you now.
10.18 That's all there is to while and do-while loops.
10.22 Let us summarize.
10.24 In this tutorial, we have learnt -


10.26 while loop and do-while loop in Perl
10.29 using sample programs.
10.31 Here is assignment for you -
10.33 Print 'Hello Perl'
10.35 till the count of variable reaches 10


10.38 by using while loop and do-while loops
10.41 Watch the video available at the following link
10.45 It summaries the Spoken Tutorial project


10.49 If you do not have good bandwidth, you can download and watch it
10.53 The Spoken Tutorial Project Team
10.56 Conducts workshops using spoken tutorials


11.00 Gives certificates to those who pass an online test


11.04 For more details, please write to contact at spoken hyphen tutorial dot org
11.12 Spoken Tutorial Project is a part of the Talk to a Teacher project


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


11.24 More information on this Mission is available spoken hyphen tutorial dot org slash NMEICT hyphen Intro
11.36 Hope you enjoyed this Perl tutorial.
11.38 This is Amol Brahmankar signing off.


11.40 Thanks for joining.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14, Sneha

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