C-and-C++/C2/Logical-Operators/English-timed

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Time Narration
00:02 Welcome to the spoken tutorial on Logical operators in C and C++.
00:08 In this tutorial we will learn about:Logical operators like Logical AND eg. expression1 && expression2
00:16 Logical OR

eg. expression1 or expression2

00:21 Logical NOT

eg. not (Expression1)

00:25 We will do this with the help of examples.
00:28 To record this tutorial, I am using:Ubuntu 11.10 as the operating system
00:33 gcc and g++ Compiler version 4.6.1 on Ubuntu.
00:39 Let us start with the introduction to the logical operators.
00:43 In C and C++, true is any value other than 0.
00:48 non zero means true
00:50 And zero means false
00:53 Expressions using logical operators return 1 for true and 0 for false.
00:58 Now I'll explain the logical operators with the help of an example.
01:03 Here is the program for logical operators in C.
01:08 Inside the main block
01:10 This statement declares the variables a,b and c as integers.
01:16 The printf statement prompts the user to enter the values of a,b and c.
01:21 The scanf statement takes input from the user for variables a, b and c.
01:28 Here, We are comparing the values of a with b and c to find the greatest.
01:33 To compare simultaneously, we use the logical AND operator.
01:38 Here, all of the conditions have to be true for logical AND to return a true value.
01:43 The expression is not evaluated further on encountering a false condition.
01:49 So, the expression (a>c) is evaluated only if (a>b) is true.
01:56 If a is less than b, then the expression won't be evaluated further.
02:02 This statement is evaluated if the previous condition is true.
02:07 Next (b>c) is evaluated.
02:10 If the condition is true, then b is greatest is displayed on the screen.
02:16 Otherwise c is greatest is displayed on the screen.
02:21 We now come to the logical OR operator.
02:24 Here, any one of the conditions has to be true for logical OR to return a true value.
02:30 The expression is not evaluated further on encountering a true condition.
02:35 So, if a == zero, then the remaining two expressions won't be evaluated.
02:43 This printf statement is executed if either of a, b or c is 0.
02:49 Coming to the end of the program. return 0 and ending curly bracket.
02:54 Now save the program.
02:57 Save it with extension .c
03:00 I have saved my file as logical.c
03:03 Open the terminal by pressing Ctrl, Alt and T keys simulataneously.
03:08 To compile the code type gcc space logical dot c space minus o space log Press enter
03:23 To execute type ./log
03:27 Press Enter.


03:29 I will enter the values as,

0

34

567

03:39 The output is displayed as,
03:42 c is greatest.
03:45 The product of a, b and c is zero.
03:50 You should try executing this program with different sets of inputs.
03:55 Now Let's write the same program in C++
03:59 I have already made the program and will take you through it.
04:03 Here is the code in C++.
04:06 Now to make the same program in C++, we make a few changes.
04:11 There's a change in the header file.
04:14 Using statement has been used.
04:18 Also there is a difference in output and input statements.
04:21 The operators behave in the same way as they did in C.


04:25 Click on Save.
04:27 Make sure the file is saved with extension .cpp
04:31 Open the terminal by pressing Ctrl, Alt and T keys simulataneously.
04:36 To compile the program type g++ logical.cpp space minus o space log1. Press Enter
04:49 to execute type ./log1
04:53 press Enter.


04:56 I will enter the values as

0

34

567

05:02 So we see the output is similar to the C program.
05:05 You should try executing the program with different sets of inputs too.
05:10 Now let us see an error which we can come across.
05:12 Let's switch to the editor.
05:16 Suppose here we forgot the brackets.
05:20 Delete this and this.
05:26 Let see what will happen, Save the program.
05:30 Come back to the terminal
05:32 Compile and execute as before
05:38 We see the error:
05:41 Expected identifier before '(' token.
05:45 This is because we have two different expressions here
05:48 We have to evaluate them as one expression using AND operator.
05:53 Now let us go back to our program and fix the error
05:57 Let us insert the brackets here and here.
06:04 Click on Save
06:06 Come back to the terminal.
06:09 Compile and execute as before
06:14 So it is working now.
06:22 Let us now summarize the tutorial.
06:24 In this tutorial we learnt about Logical AND eg. ((a > b) && (a > c))


06:32 Logical OR

eg. (a == 0 || b == 0 || c == 0)


06:39 Assignment
06:41 Write a program that takes two numbers as input from the user.
06:44 Check whether the two numbers are equal or not using NOT operator. Hint: (a != b)
06:54 Watch the video available at the following link
06:57 It summarises the Spoken Tutorial project
06:59 If you do not have good bandwidth, you can download and watch it


07:03 The Spoken Tutorial Project Team * Conducts workshops using spoken tutorials
07:07 Gives certificates for those who pass an online test
07:11 For more details, please write to contact at spoken hyphen tutorial dot org
07:18 Spoken Tutorial Project is a part of the Talk to a Teacher project
07:21 It is supported by the National Mission on Education through ICT, MHRD, Government of India
07:27 More information on this Mission is available at
07:30 spoken hyphen tutorial dot org slash NMEICT hyphen Intro


07:37 This is Ritwik Joshi from IIT Bombay.

Thank you for joining.

Contributors and Content Editors

Ashwini, PoojaMoolya, Pratik kamble, Sandhya.np14