C-and-C++/C2/Logical-Operators/English-timed
From Script | Spoken-Tutorial
| 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 e.g. 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 (dot c). |
| 03:00 | I have saved my file as logical.c. |
| 03:03 | Open the terminal by pressing Ctrl, Alt and T keys simultaneously. |
| 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 (dot slash 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 (dot cpp). |
| 04:31 | Open the terminal by pressing Ctrl, Alt and T keys simultaneously. |
| 04:36 | To compile the program type g++ logical.cpp space minus o space log1. Press Enter. |
| 04:49 | To execute, type ./log1 (dot slash 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's 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 summaries 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 to 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. |
