View source for C-and-C++/C2/Logical-Operators/English-timed

{| border=1
|| 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.

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| 02:57
|'''Save''' it with extension '''.c''' (dot c).

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| 03:00
|I have saved my file as '''logical.c'''.

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| 03:03
|   Open the terminal by pressing '''Ctrl, Alt''' and '''T '''keys simultaneously.

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| 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)

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| 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++.

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|  03:59
| I have already made the program and will take you through it.

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| 04:03
|Here is the code in '''C++'''.

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| 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.

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| 04:14
|'''using''' statement has been used.

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| 04:18
|Also there is a difference in output and input statements.

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| 04:21
|The operators behave in the same way as they did in C.

|-
| 04:25
|  Click on '''Save'''.

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| 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.

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|  05:16
|  Suppose here we forgot the brackets.

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| 05:20
|Delete this and this.

|-
|  05:26
| Let see what will happen, Save the program.

|-
| 05:30
|Come back to the terminal.

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| 05:32
|Compile and execute as before.

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| 05:38
|  We see the error:

|-
| 05:41
|'''Expected identifier before '(' token'''.

|-
|  05:45
|  This is because we have two different expressions here.

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| 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. 

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| 06:04
|Click on '''Save'''.

|-
| 06:06
|Come back to the terminal.

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|  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,

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| 06:41
|Write a program that takes two numbers as input from the user.

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| 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 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. 

|}