Difference between revisions of "BASH/C2/Conditional-Loops/English-timed"

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| 00:01
 
| 00:01
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| Dear friends, welcome to the spoken tutorial on '''loops''' in '''BASH'''.
+
| Dear friends, welcome to the '''spoken tutorial''' on '''loops''' in '''BASH'''.
  
 
|-
 
|-
 
| 00:07   
 
| 00:07   
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|  In this tutorial, we will learn
+
|  In this tutorial, we will learn:
  
 
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|-
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|-
 
|-
 
| 00:11   
 
| 00:11   
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| * '''while loop'''<br/> with a few examples
+
| * '''while loop'''<br/> with a few examples.
 
|-
 
|-
 
| 00:15
 
| 00:15
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| To record this tutorial I am using,
+
| To record this tutorial, I am using:
  
 
|-
 
|-
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|-
 
|-
 
| 00:34  
 
| 00:34  
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|  Let us start with an introduction to ''' loops'''
+
|  Let us start with an introduction to ''' loops'''.
  
 
|-
 
|-
 
| 00:37  
 
| 00:37  
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| '''Loops''' are used to execute a group of statements repeatedly.
+
| '''Loops''' are used to '''execute''' a group of '''statements''' repeatedly.
  
 
|-
 
|-
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|-
 
|-
 
| 00:51
 
| 00:51
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| And this is the end of '''for loop'''.
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| and this is the end of '''for loop'''.
  
 
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|-
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| 01:06
 
| 01:06
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| And end of '''for loop'''.
+
| and end of '''for loop'''.
  
 
|-
 
|-
 
| 01:09
 
| 01:09
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|   Let us see an example of '''for loop''' using the first syntax.
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| Let us see an example of '''for loop''' using the first syntax.
  
 
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|-
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| 01:20  
 
| 01:20  
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|  Note that our filename is '''for.sh'''
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|  Note that our filename is '''for.sh'''.
  
 
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|-
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|-
 
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| 01:28
 
| 01:28
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|  The variable '''number''' will store the value given by user.  
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|  The variable '''number''' will store the '''value''' given by user.  
  
 
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|-
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|-
 
|  01:37
 
|  01:37
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| Now, we initialize the variable '''sum''' as zero.
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| Now, we initialize the '''variable''' '''sum''' as zero.
  
 
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|-
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|-
 
|-
 
| 01:54
 
| 01:54
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|  Now here, we calculate the '''sum''' as '''sum plus i'''.
+
|  Now here, we calculate the '''sum''' as '''sum plus i'''
  
 
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|-
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|-
 
| 02:03   
 
| 02:03   
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|  After this, we increment the value of '''i''' by '''1'''.
+
|  After this, we increment the '''value''' of '''i''' by '''1'''.
  
 
|-
 
|-
 
| 02:08
 
| 02:08
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|  And then we check the condition till this condition is '''false'''.
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|  And then we check the '''condition''' till this '''condition''' is '''False'''.
 
|-
 
|-
 
|  02:14
 
|  02:14
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|-
 
|-
 
|  02:19
 
|  02:19
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|  Let us execute the program and observe what happens.
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|  Let us '''execute''' the program and observe what happens.
  
 
|-
 
|-
 
| 02:24   
 
| 02:24   
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|  On the '''terminal''' type - '''chmod +x for.sh'''
+
|  On the '''terminal''', type - '''chmod +x for.sh'''
  
 
|-
 
|-
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|-
 
|-
 
|  02:36   
 
|  02:36   
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|  I will enter '''5''' as the input number.
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|  I will enter '''5''' as the '''input''' number.
  
 
|-
 
|-
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|-
 
|-
 
|  02:46   
 
|  02:46   
−
| After that, the last line of the output is displayed:
+
| After that, the last line of the '''output''' is displayed:
  
 
|-
 
|-
 
|  02:50
 
|  02:50
−
| '''Sum of first n numbers is 15'''
+
| '''Sum of first n numbers is 15'''.
  
 
|-
 
|-
 
|  02:54
 
|  02:54
−
| Now let us see the flow of the program.
+
| Now, let us see the flow of the program.
  
 
|-
 
|-
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|-
 
|-
 
|  03:00
 
|  03:00
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|  First we have value of '''i''' as '''1'''.
+
|  First, we have value of '''i''' as '''1'''.
  
 
|-
 
|-
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|-
 
|-
 
|  03:10
 
|  03:10
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| Since the condition is '''true,''' we calculate '''sum''' as ''' 0 + 1.'''
+
| Since the condition is '''True,''' we calculate '''sum''' as ''' 0 + 1.'''
  
 
|-
 
|-
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|-
 
|-
 
|  03:36  
 
|  03:36  
−
| The condition is '''true''' and now sum will be ''' 1 + 2 ''' i.e ''' 3.'''
+
| The '''condition''' is '''True''' and now '''sum''' will be ''' 1 + 2 ''' i.e ''' 3.'''
  
 
|-
 
|-
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|-
 
|-
 
| 03:55  
 
| 03:55  
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|  The script will continue to add the next value of ''' i ''' to the previous value in ''' sum.'''
+
|  The '''script''' will continue to add the next value of ''' i ''' to the previous value in ''' sum.'''
  
 
|-
 
|-
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|-
 
|-
 
| 04:20   
 
| 04:20   
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| I have written the code in this file and named it as '''for-loop.sh'''
+
| I have written the '''code''' in this file and named it as '''for-loop.sh'''
  
 
|-
 
|-
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|-
 
|-
 
| 04:37  
 
| 04:37  
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| '''ls''' command lists the directory content.
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| ''' 'ls' ''' '''command''' lists the directory content.
  
 
|-
 
|-
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|-
 
|-
 
| 04:46  
 
| 04:46  
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| This will list all the files present in your home directory.
+
| This will list all the files present in your '''home directory'''.
  
 
|-
 
|-
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|-
 
|-
 
| 04:53
 
| 04:53
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|  Let us execute the script on the '''terminal''' by typing -  
+
|  Let us '''execute''' the '''script''' on the '''terminal''' by typing -  
  
 
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|-
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|-
 
|-
 
| 05:27
 
| 05:27
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| This means that the '''while loop''' will execute as long as the condition is '''true.'''
+
| This means that the '''while loop''' will execute as long as the condition is '''True.'''
  
 
|-
 
|-
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|-
 
|-
 
|  05:37
 
|  05:37
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| Here I have named it as '''while.sh'''
+
| Here I have named it as '''while.sh'''.
  
 
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|-
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|-
 
|-
 
|05:49
 
|05:49
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| Let us go through the code.
+
| Let us go through the '''code'''.
  
 
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|-
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|-
 
|06:06
 
|06:06
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|Now this is the '''while condition.'''
+
|Now, this is the '''while''' '''condition'''.
  
 
|-
 
|-
 
| 06:08
 
| 06:08
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| Here we check whether '''i''' is '''less than or equal''' to value of '''number''' given by the user.
+
| Here, we check whether '''i''' is '''less than or equal''' to value of '''number''' given by the user.
  
 
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|  06:33  
 
|  06:33  
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| And the while loop is repeated till the value of '''i''' exceeds the value of '''number.'''
+
| And the '''while loop''' is repeated till the value of '''i''' exceeds the value of '''number.'''
 
|-
 
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|  06:40  
 
|  06:40  
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| '''Sum of even numbers within the given range is 56.'''
 
| '''Sum of even numbers within the given range is 56.'''
  
−
|---[[User:PoojaMoolya|PoojaMoolya]] ([[User talk:PoojaMoolya|talk]]) 12:11, 8 December 2014 (IST)
 
 
|  07:11  
 
|  07:11  
−
|  Let me resize the window and explain the output.
+
|  Let me resize the window and explain the '''output'''.
  
 
|-
 
|-
 
| 07:14  
 
| 07:14  
−
|  First we check whether '''i''' which is '''0,''' is less than or equal to the '''number''', which is '''15'''.
+
|  First we check whether '''i''' which is '''0,''' is less than or equal to the '''number''' which is '''15'''.
  
 
|-
 
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|  07:24  
 
|  07:24  
−
|  The condition is '''true,''' hence '''sum''' will be '''0+0''' i.e '''0.'''
+
|  The '''condition''' is '''True.''' Hence '''sum''' will be '''0+0''' i.e '''0.'''
  
 
|-
 
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|  07:31
 
|  07:31
−
| Now '''i''' will be incremented by '''2''' and the '''new''' value of ''' i ''' is ''' 2.'''
+
| Now '''i''' will be incremented by '''2''' and the new value of ''' i ''' is ''' 2.'''
  
 
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|  07:43  
 
|  07:43  
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|  The condition again is '''true;''' so we add '''0+2.'''
+
|  The condition again is '''True;''' so we add '''0+2.'''
  
 
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|  07:56
 
|  07:56
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| So now value of '''i''' will be '''2+2''' i.e '''4.'''
+
| So, now value of '''i''' will be '''2+2''' i.e '''4.'''
  
 
|-
 
|-
 
|  08:03
 
|  08:03
−
|  And the next value of ''' sum ''' will be '''4+2''' I.e '''6.'''
+
|  And the next value of ''' sum ''' will be '''4+2''' i.e '''6.'''
  
 
|-
 
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|  08:09
 
|  08:09
−
|  In the same way, the script will continue to add '''2''' to the previous value of '''i, '''till it exceeds '''15'''.
+
|  In the same way, the '''script''' will continue to add '''2''' to the previous value of '''i, '''till it exceeds '''15'''.
  
 
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| 08:27   
 
| 08:27   
−
| Let us summarize
+
| Let us summarize.
  
 
|-
 
|-
 
| 08:28   
 
| 08:28   
−
| In this tutorial we learnt two different syntax of '''for loop ''' and we also learnt about the '''while loop.'''
+
| In this tutorial, we learned two different syntax of '''for loop ''' and we also learned about the '''while loop.'''
  
 
|-
 
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| 08:38   
 
| 08:38   
−
| Find the sum of the first "n" prime numbers.
+
| find the sum of the first "n" prime numbers.
  
 
|-
 
|-
 
|  08:43  
 
|  08:43  
−
|  Watch the video available at the link shown below
+
|  Watch the video available at the link shown below.
  
 
|-
 
|-
 
|  08:46  
 
|  08:46  
−
| It summarises the Spoken Tutorial project  
+
| It summarizes the Spoken-Tutorial project.
  
 
|-
 
|-
 
|  08:50
 
|  08:50
−
| 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.
  
 
|-
 
|-
 
| 08:54   
 
| 08:54   
−
|  The Spoken Tutorial Project Team
+
|  The Spoken Tutorial Project team:
  
 
|-
 
|-
 
| 08:56   
 
| 08:56   
−
| Conducts workshops using spoken tutorials  
+
| Conducts workshops using spoken tutorials.
  
 
|-
 
|-
 
| 09:00   
 
| 09:00   
−
| Gives certificates to those who pass an online test  
+
| Gives certificates to those who pass an online test.
  
 
|-
 
|-
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|-
 
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|  09:11  
 
|  09:11  
−
|  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.
  
 
|-
 
|-
 
|  09:14  
 
|  09:14  
−
| 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.
  
 
|-
 
|-
 
|  09:22  
 
|  09:22  
−
| More information on this Mission is available at the link shown below.
+
| More information on this mission is available at the link shown below.
  
 
|-
 
|-
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|  09:34  
 
|  09:34  
−
|  This is Ashwini Patil from IIT Bombay signning off.
+
|  This is Ashwini Patil from IIT Bombay, signing off.
  
 
|-
 
|-

Revision as of 18:24, 3 July 2015

Title of script: Basic If loop in BASH Author: Ashwini Patil Keywords: video tutorial, for loop, while loop

Time Narration
00:01 Dear friends, welcome to the spoken tutorial on loops in BASH.
00:07 In this tutorial, we will learn:
00:09 * for loop
00:11 * while loop
with a few examples.
00:15 To record this tutorial, I am using:
00:18 * Ubuntu Linux 12.04 Operating System
00:22 * GNU BASH version 4.1.10
00:26 Please note,GNU bash version 4 or above is recommended to practice this tutorial.
00:34 Let us start with an introduction to loops.
00:37 Loops are used to execute a group of statements repeatedly.
00:43 Let us see the syntax.
00:45 for expression 1, 2, 3
00:49 statement 1, 2, 3
00:51 and this is the end of for loop.
00:55 An alternate syntax of for loop is:
00:58 for variable in sequence/range
01:03 statement 1, 2, 3
01:06 and end of for loop.
01:09 Let us see an example of for loop using the first syntax.
01:14 In this program, we will calculate the sum of first n numbers.
01:20 Note that our filename is for.sh.
01:25 This is our shebang line.
01:28 The variable number will store the value given by user.
01:34 The value is an integer here.
01:37 Now, we initialize the variable sum as zero.
01:42 This is where we begin the for loop.
01:45 First, we initialize i to 1.
01:48 Then we check whether i is less than or equal to number.
01:54 Now here, we calculate the sum as sum plus i
02:00 and then we print it.
02:03 After this, we increment the value of i by 1.
02:08 And then we check the condition till this condition is False.
02:14 On exiting the for loop, this message is printed.
02:19 Let us execute the program and observe what happens.
02:24 On the terminal, type - chmod +x for.sh
02:31 Then type: ./for.sh
02:36 I will enter 5 as the input number.
02:40 The sum that is calculated for each value of i is displayed.
02:46 After that, the last line of the output is displayed:
02:50 Sum of first n numbers is 15.
02:54 Now, let us see the flow of the program.
02:57 Let me resize the windows.
03:00 First, we have value of i as 1.
03:04 Then we check whether 1 is less than or equal to 5.
03:10 Since the condition is True, we calculate sum as 0 + 1.
03:16 Now we have sum as 1.
03:20 Then we print sum i.e 1.
03:24 Next, i is incremented by 1 and the new value of i is 2.
03:31 Then we check whether 2 is less than or equal to 5.
03:36 The condition is True and now sum will be 1 + 2 i.e 3.
03:44 i is then incremented by 1 and then the new value of i is 3.
03:51 And we get sum as 6.
03:55 The script will continue to add the next value of i to the previous value in sum.
04:02 This will continue till i<=5 is false.
04:09 On exiting the for loop, the final message is printed.
04:14 Let us see another example of for loopusing the second syntax.
04:20 I have written the code in this file and named it as for-loop.sh
04:27 This simple program will list the files in a directory.
04:32 This is the shebang line.
04:35 Then we have for loop.
04:37 'ls' command lists the directory content.
04:41 -1 (hyphen one) lists one file per line.
04:46 This will list all the files present in your home directory.
04:51 This is the end of for loop.
04:53 Let us execute the script on the terminal by typing -
04:58 chmod +x for-loop.sh
05:04 ./for-loop.sh
05:09 This will display all the files present in the Home directory.
05:14 Now, we will learn about while loop.
05:18 Let us understand the syntax first.
05:21 while condition

statement 1, 2, 3 End of while loop.

05:27 This means that the while loop will execute as long as the condition is True.
05:34 Let us see an example of while loop.
05:37 Here I have named it as while.sh.
05:42 In this program, we will calculate the sum of even numbers within a given range.
05:49 Let us go through the code.
05:52 Here, we accept a number from the user and store it in variable number.
05:59 Next, we declare variables i and sum and initialize them to 0 (zero).
06:06 Now, this is the while condition.
06:08 Here, we check whether i is less than or equal to value of number given by the user.
06:17 Then we calculate the sum by adding value of i to value of sum.
06:24 Next, we increment the value of i with 2.
06:28 This will ensure that we only add the even numbers.
06:33 And the while loop is repeated till the value of i exceeds the value of number.
06:40 When we exit the while loop, we print the sum of all the even numbers within the given range.
06:47 Let us execute the program.
06:50 Type on the terminal:
06:52 chmod +x while.sh
06:56 ./while.sh
07:00 I will give 15 as my input.
07:04 The last line of the output is:
07:06 Sum of even numbers within the given range is 56. 07:11 Let me resize the window and explain the output.
07:14 First we check whether i which is 0, is less than or equal to the number which is 15.
07:24 The condition is True. Hence sum will be 0+0 i.e 0.
07:31 Now i will be incremented by 2 and the new value of i is 2.
07:37 Then we check if 2 is less than or equal to 15.
07:43 The condition again is True; so we add 0+2.
07:49 Now sum has the value 2.
07:52 Again the value of i will be incremented by 2.
07:56 So, now value of i will be 2+2 i.e 4.
08:03 And the next value of sum will be 4+2 i.e 6.
08:09 In the same way, the script will continue to add 2 to the previous value of i, till it exceeds 15.
08:18 And we get the total value in sum as 56.
08:24 This brings us to the end of this tutorial.
08:27 Let us summarize.
08:28 In this tutorial, we learned two different syntax of for loop and we also learned about the while loop.
08:37 As an assignment -
08:38 find the sum of the first "n" prime numbers.
08:43 Watch the video available at the link shown below.
08:46 It summarizes the Spoken-Tutorial project.
08:50 If you do not have good bandwidth, you can download and watch it.
08:54 The Spoken Tutorial Project team:
08:56 Conducts workshops using spoken tutorials.
09:00 Gives certificates to those who pass an online test.
09:04 For more details, please write to contact@spoken-tutorial.org
09:11 Spoken Tutorial Project is a part of the Talk to a Teacher project.
09:14 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
09:22 More information on this mission is available at the link shown below.
09:28 The script has been contributed by Fossee and spoken-tutorial team.
09:34 This is Ashwini Patil from IIT Bombay, signing off.
09:38 Thank You for joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Ranjana, Sandhya.np14

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