View source for C-and-C++/C2/If-And-Else-If-statement/English-timed

{| border=1
|| Time
|| Narration

|-
|  00:02
|  Welcome to the spoken tutorial on '''Conditional statements in C and C++'''.

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|  00:08
|  In this tutorial we will learn: 

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|  00:11
| How to execute a single '''statement'''

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|  00:14
| How to execute group of '''statements'''.

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|  00:16
| We will do this through examples.

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|  00:19
| We will also see some common errors and their solutions.

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|  00:25
|  To record this tutorial, I am using '''Ubuntu Operating system''' version 11.10.

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|  00:31
| '''gcc''' and '''g++ Compiler''' version 4.6.1. 

|-
| 00:38
| Let us start with the introduction to conditional '''statements'''. 

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|  00:43 
| A '''statement''' in a program controls the flow of program execution.

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|  00:49
| It helps to make decision on what code is to be executed.

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|  00:55
|We can check the conditions, whether true or false.

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|  01:00
| We can execute a single statement or a group of statements.

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| 01:07
| Let us understand the flow of '''if''' statements.

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|  01:13
| Here, if the condition is true then '''statement 1''' will be executed.

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|  01:20
| If the condition is false then '''statement 2''' will be executed. 

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|  01:29
| Now we will see the flow of '''else if''' statement.

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|  01:32	
| Here, if '''condition 1''' is true then '''statement 1''' will be executed.

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|  01:41
| If '''condition 1''' is false then it will check for another condition that is '''condition 2'''.

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|  01:49
| If '''condition 2''' is true then '''statement 3''' will be executed.

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|  01:54
| And If '''condition 2''' is false then '''statement 2''' will be executed.

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|  02:02
|  Now Let us move on to our program.

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|  02:06	
| I have already typed the code on the editor.

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|  02:09 
| So, let me open it.

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|  02:13
| Note that our file name is '''ifstmt.c'''.

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|  02:18
| In this program we will calculate the sum of two numbers and will check a few conditions.

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|  02:26
|  Let me explain the code now. 

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|  02:30
| This is our '''header file.'''

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|  02:34
|  This is our '''main()''' function.

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| 02:38 
|  Here we have declared three '''integer variables''' '''a, b''' and '''sum.'''

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|  02:46
| Here we are asking for user input.

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|  02:49
| User will enter the values of a and b. 

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|  02:52
| The values will be stored in '''variable a''' and '''variable b.'''

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|  02:58
|The '''scanf()''' function reads data from the console.

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|  03:02
| It then stores the result in the given '''variable.'''

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|  03:06
| The '''format specifier''' in the '''scanf()''' helps to know the type of data.

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|  03:10
| Like here we have '''%d''', it denotes that we are dealing with integer data type.

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|  03:18
|  Here we add the values of '''a''' and '''b.'''

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| 03:22
| We will store the result in '''sum.'''

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|  03:25
|  Then we print the result.

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|  03:29
|  This is our '''if''' statement.

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|  03:30
|Here, we check the condition whether '''sum''' is greater than 20.

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|  03:36
|If the condition is true, then we print '''Sum''' is greater than 20.

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|  03:42
|  Now let me comment out these lines.

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|03:48
|This is our '''return''' statement.

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|  03:51
| Now click on '''Save'''. 

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|  03:53
|First we will see the execution of '''if''' statement.

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|  03:58
| Please open the terminal window by pressing '''Ctrl, Alt''' and '''T''' keys simultaneously on your keyboard.

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|04:09
| To compile, type '''gcc space ifstmt dot c space  -o space if''' and press Enter.

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| 04:20
| To execute,  type '''./if''' (dot slash if). Press Enter.

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| 04:26
|   It is displayed as '''Enter the values of a and b'''.

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|  04:31
|I will give the values as 10 and 12.

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|  04:38
|The output is displayed as '''Sum of a and b is 22. Sum is greater than 20'''.

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| 04:45
|  Now come back to our program.

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|  04:48
|  We will check another condition.

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|  04:52
|Let me remove the comment from here.

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|  04:56
|I will give the comment here.

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|  05:00
|Now click on '''Save.'''  This is our '''else-if''' statement. 

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|  05:05
|Here, we check another condition whether '''Sum''' is greater than 10.  

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|  05:11
|If the condition is true then we print 'Sum is greater than 10 and less than 20'.

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| 05:18
|  Now come back to our terminal.

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|  05:20
|Let us compile as before. 
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|  05:23
|Let us execute as before.

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|  05:26
| It is displayed as

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|  05:28
|'''Enter the value of a and b'''.
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|  05:30
| I will give the values as 10 and 2.

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|  05:35
|The output is displayed as: '''Sum of a and b is 12'''. 

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|  05:38
|'''Sum is greater than 10 and less than 20'''.

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| 05:42
|Let me clear the prompt. 

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| 05:44
| Now come back to our program.

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|  05:48
|  I will remove the comment from here and here. Now click on Save.

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|  05:56
| If both the above conditions are false then we print 'Sum is less than 10'.

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|  06:04
|This is our '''else''' statement.

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|  06:07
| Now let us execute and see.  Come back to our terminal.

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| 06:11
|Let us compile as before. Let us execute as before.

|-
|  06:18
| Here it is displayed as '''Enter the value of a and b'''.

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|  06:22
|I will give the values as 3 and 5.

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|  06:27
| The output is displayed as '''sum of a and b is 8'''. 

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|  06:31
|'''Sum is less than 10'''.

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|  06:34
|  Now we will see some common errors which we can come across.

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|  06:38	
|Come back to our program.

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|  06:41
| Suppose, here at the end of '''if''' statement I will type a semicolon (;).

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|  06:47
|Let us see what will happen. Click on '''Save.'''

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|  06:50
|  Let us execute. Come back to our terminal.

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|  06:53
|Let us compile as before. 

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|  06:56
|  We see an error: ''' 'else' without a previous 'if' '''

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| 07:02
| Come back to our program. It is a syntax error.

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|  07:07
|'''if''' statement will never terminate with a semicolon.

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|  07:10
|And the '''else if''' statement will never work without an '''if'''.

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| 07:16
|  Let us fix the error. Delete the semicolon (;) here.

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| 07:22
|  Now Click on '''Save.'''

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|  07:25
|   Let us execute. Come back to the terminal.

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| 07:29
|  Let us compile as before. Let us execute as before.

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|  07:35
|Enter the value of a and b.

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|  07:37
|I will give the values as 3 and 6.

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|  07:43
|The output is displayed as 

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|  07:45
|'''Sum of a and b is 9. Sum is less than 10'''.

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|   07:52
| NOW WE WILL SEE HOW TO EXECUTE THE SAME PROGRAM IN C++. 

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|  07:57
|Come back to our program.

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|  07:59
| I will change a few things here.

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| 08:03
|  Press '''Shift, Ctrl''' and '''S'''  keys simultaneously on your keyboard. 

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|  08:11
|Now save the file with an extension '''dot cpp''' and click on ''' Save'''.

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|  08:20
| We will change the header file as '''iostream'''.

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| 08:26 
|  Let us include the '''using '''statement here.

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|  08:30
|   Now click on the Search for and replace text option. 
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|  08:35
|Let us replace the '''printf '''statement with the '''cout''' statement.

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|  08:40
|Click on '''Replace all''' and click on Close.

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|  08:46
|  Now delete the closing brackets here.

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|  08:49
|Replace the '''scanf()''' statement with the '''cin''' statement.

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|  08:54 	
|Type '''cin''' and '''two closing angle brackets >>'''.

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| 09:00  
|As we use '''cin >>''' function to read a line in C++. 
 
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| 09:05
| Now delete the '''format specifiers'''.

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|  09:09
|Delete the '''comma''' and '''ampersand &'''.

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|  09:12
|Delete the comma here and type two closing angle brackets.

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|  09:17
|Again delete the '''ampersand'''and the closing brackets. Now click on '''Save'''.

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| 09:25
|  Here delete the closing bracket and the comma.

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|  09:31
|Now delete the '''backslash n (\n)''' and '''format specifier'''.
 
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|  09:37	 
| Now type two opening brackets. 

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|  09:42
|Again type two opening angle brackets  and '''within the double quotes type backslash n “\n”.'''

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|  09:49
|Here also we will delete the closing bracket.

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|  09:53
|Now again delete the closing bracket here and here.

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|  09:59 
|Now click on '''Save'''.

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| 10:02
| Let us execute.

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|  10:04 	
|| Come back to the terminal. Let me clear the prompt.

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|  10:10
|To compile, type '''g++ space ifstmt.cpp space -o space if1'''

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|  10:20
|Here we have 'if1' because we don't want to overwrite the output parameter '''if '''for the file 'ifstmt.c'.

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|  10:31
|Now Press 'Enter'.To execute type '''./if1''' (dot slash if1) and press '''Enter'''.

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|  10:39
|Enter the value of '''a''' and '''b'''. I will give the values as 20 and 10.

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|  10:48
|The output is displayed as '''Sum of a and b is 30'''

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|  10:52
|'''Sum is greater than 20'''

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|  10:56
|This brings us to the end of this tutorial.

|-
|  10:59
|  Now come back to our slides.

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| 11:02 
|  Let us summarize.

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|  11:04
|In this tutorial we learned 'if' statement eg. if(condition),

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|  11:11
| And 'else if' statement eg. else if(condition).

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|  11:17
|  As an assignment, Write a program to check 'a' is greater than 'b' or less than 'b'.

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|  11:24
|Hint: use 'if' statement.

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|  11:28
|Write another program to check which value is greater 'a', 'b' or 'c'. 

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|  11:34
|Hint: use 'else-if' statement.

|-
|  11:38
|  Watch the video available at the link shown below. 

|- 
|  11:41
|It summarizes the Spoken Tutorial project. 

|-
|  11:44
|If you do not have good bandwidth, you can download and watch it.

|-
|11:48
|| The Spoken Tutorial Project Team,

|-
|  11:50
|Conducts workshops using spoken tutorials. 

|-
|  11:54
|Gives certificates to those who pass an online test. 

|-
|  11:57
|For more details, please write to, contact @ spoken hyphen tutorial dot org.

|-
|  12:04
|  Spoken Tutorial Project is a part of the Talk to a Teacher project.

|-
|  12:09
|It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|-
|  12:15
|More information on this Mission is available at the link shown below.  

|-
| 12:20
| This is Ashwini Patil from IIT Bombay.

Thank You for watching.
|}