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

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Time Narration
00:02 Welcome to the spoken tutorial on Conditional statements in C and C++.
00:08 In this tutorial we will learn:
00:11 How to execute a single statement
00:14 How to execute group of statements.
00:16 We will do this through examples.
00:19 We will also see some common errors and their solutions.
00:25 To record this tutorial, I am using Ubuntu Operating system version 11.10.
00:31 gcc and g++ Compiler version 4.6.1.
00:38 Let us start with the introduction to conditional statements.
00:43 A statement in a program controls the flow of program execution.
00:49 It helps to make decision on what code is to be executed.
00:55 We can check the conditions, whether true or false.
01:00 We can execute a single statement or a group of statements.
01:07 Let us understand the flow of if statements.
01:13 Here, if the condition is true then statement 1 will be executed.
01:20 If the condition is false then statement 2 will be executed.
01:29 Now we will see the flow of else if statement.
01:32 Here, if condition 1 is true then statement 1 will be executed.
01:41 If condition 1 is false then it will check for another condition that is condition 2.
01:49 If condition 2 is true then statement 3 will be executed.
01:54 And If condition 2 is false then statement 2 will be executed.
02:02 Now Let us move on to our program.
02:06 I have already typed the code on the editor.
02:09 So, let me open it.
02:13 Note that our file name is ifstmt.c.
02:18 In this program we will calculate the sum of two numbers and will check a few conditions.
02:26 Let me explain the code now.
02:30 This is our header file.
02:34 This is our main() function.
02:38 Here we have declared three integer variables a, b and sum.
02:46 Here we are asking for user input.
02:49 User will enter the values of a and b.
02:52 The values will be stored in variable a and variable b.
02:58 The scanf() function reads data from the console.
03:02 It then stores the result in the given variable.
03:06 The format specifier in the scanf() helps to know the type of data.
03:10 Like here we have %d, it denotes that we are dealing with integer data type.
03:18 Here we add the values of a and b.
03:22 We will store the result in sum.
03:25 Then we print the result.
03:29 This is our if statement.
03:30 Here, we check the condition whether sum is greater than 20.
03:36 If the condition is true, then we print Sum is greater than 20.
03:42 Now let me comment out these lines.
03:48 This is our return statement.
03:51 Now click on Save.
03:53 First we will see the execution of if statement.
03:58 Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
04:09 To compile, type gcc space ifstmt dot c space -o space if and press Enter.
04:20 To execute, type ./if (dot slash if). Press Enter.
04:26 It is displayed as Enter the values of a and b.
04:31 I will give the values as 10 and 12.
04:38 The output is displayed as Sum of a and b is 22. Sum is greater than 20.
04:45 Now come back to our program.
04:48 We will check another condition.
04:52 Let me remove the comment from here.
04:56 I will give the comment here.
05:00 Now click on Save. This is our else-if statement.
05:05 Here, we check another condition whether Sum is greater than 10.
05:11 If the condition is true then we print 'Sum is greater than 10 and less than 20'.
05:18 Now come back to our terminal.
05:20 Let us compile as before.
05:23 Let us execute as before.
05:26 It is displayed as
05:28 Enter the value of a and b.
05:30 I will give the values as 10 and 2.
05:35 The output is displayed as: Sum of a and b is 12.
05:38 Sum is greater than 10 and less than 20.
05:42 Let me clear the prompt.
05:44 Now come back to our program.
05:48 I will remove the comment from here and here. Now click on Save.
05:56 If both the above conditions are false then we print 'Sum is less than 10'.
06:04 This is our else statement.
06:07 Now let us execute and see. Come back to our terminal.
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.
06:22 I will give the values as 3 and 5.
06:27 The output is displayed as sum of a and b is 8.
06:31 Sum is less than 10.
06:34 Now we will see some common errors which we can come across.
06:38 Come back to our program.
06:41 Suppose, here at the end of if statement I will type a semicolon (;).
06:47 Let us see what will happen. Click on Save.
06:50 Let us execute. Come back to our terminal.
06:53 Let us compile as before.
06:56 We see an error: 'else' without a previous 'if'
07:02 Come back to our program. It is a syntax error.
07:07 if statement will never terminate with a semicolon.
07:10 And the else if statement will never work without an if.
07:16 Let us fix the error. Delete the semicolon (;) here.
07:22 Now Click on Save.
07:25 Let us execute. Come back to the terminal.
07:29 Let us compile as before. Let us execute as before.
07:35 Enter the value of a and b.
07:37 I will give the values as 3 and 6.
07:43 The output is displayed as
07:45 Sum of a and b is 9. Sum is less than 10.
07:52 NOW WE WILL SEE HOW TO EXECUTE THE SAME PROGRAM IN C++.
07:57 Come back to our program.
07:59 I will change a few things here.
08:03 Press Shift, Ctrl and S keys simultaneously on your keyboard.
08:11 Now save the file with an extension dot cpp and click on Save.
08:20 We will change the header file as iostream.
08:26 Let us include the using statement here.
08:30 Now click on the Search for and replace text option.
08:35 Let us replace the printf statement with the cout statement.
08:40 Click on Replace all and click on Close.
08:46 Now delete the closing brackets here.
08:49 Replace the scanf() statement with the cin statement.
08:54 Type cin and two closing angle brackets >>.
09:00 As we use cin >> function to read a line in C++.
09:05 Now delete the format specifiers.
09:09 Delete the comma and ampersand &.
09:12 Delete the comma here and type two closing angle brackets.
09:17 Again delete the ampersandand the closing brackets. Now click on Save.
09:25 Here delete the closing bracket and the comma.
09:31 Now delete the backslash n (\n) and format specifier.
09:37 Now type two opening brackets.
09:42 Again type two opening angle brackets and within the double quotes type backslash n “\n”.
09:49 Here also we will delete the closing bracket.
09:53 Now again delete the closing bracket here and here.
09:59 Now click on Save.
10:02 Let us execute.
10:04 Come back to the terminal. Let me clear the prompt.
10:10 To compile, type g++ space ifstmt.cpp space -o space if1
10:20 Here we have 'if1' because we don't want to overwrite the output parameter if for the file 'ifstmt.c'.
10:31 Now Press 'Enter'.To execute type ./if1 (dot slash if1) and press Enter.
10:39 Enter the value of a and b. I will give the values as 20 and 10.
10:48 The output is displayed as Sum of a and b is 30
10:52 Sum is greater than 20
10:56 This brings us to the end of this tutorial.
10:59 Now come back to our slides.
11:02 Let us summarize.
11:04 In this tutorial we learned 'if' statement eg. if(condition),
11:11 And 'else if' statement eg. else if(condition).
11:17 As an assignment, Write a program to check 'a' is greater than 'b' or less than 'b'.
11:24 Hint: use 'if' statement.
11:28 Write another program to check which value is greater 'a', 'b' or 'c'.
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.
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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.