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

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.

Contributors and Content Editors

Ashwini, PoojaMoolya, Pratik kamble, Sandhya.np14