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

'''Title of script''': Logical Operators in C and C++

'''Author:Ritwik Joshi '''

'''Keywords: Logical Operators, Video Tutorial'''



{| style="border-spacing:0;"
| style="border-top:0.002cm solid #000000;border-bottom:0.002cm solid #000000;border-left:0.002cm solid #000000;border-right:none;padding:0.097cm;"| <center>'''Visual Cue'''</center>
| style="border:0.002cm solid #000000;padding:0.097cm;"| <center>'''Narration'''</center>
|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 1
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Welcome to the spoken tutorial on '''Logical operators in C and C++.'''

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 2
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial we will learn about:

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 3
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To record this tutorial, I am using:

'''Ubuntu 11.10''' as the operating system 

'''gcc''' and '''g++ Compiler '''version '''4.6.1 on''' '''Ubuntu.'''

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 4


'''Non zero = True'''


'''Zero = False'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us start with the introduction to the '''logical operators'''.

In '''C '''and '''C++,''' '''true''' is any value other than 0.

non zero means true

'''Non zero = True'''

zero means false

'''Zero = False'''


Expressions using logical operators return 1 for '''true''' and 0 for '''false'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now I'll explain the logical operators with the help of an example.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Switch to '''logical.c''' in gedit
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here is the program for '''logical operators''' in '''C'''.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''int a,b,c; '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Inside the main block

This statement declares the variables '''a''','''b''' and '''c''' as integers.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''printf("Enter the values of a,b'''

'''and c \n"); '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The '''printf''' statement prompts the user to enter the values of '''a''','''b''' and '''c'''.

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''scanf("%d %d %d", &a, &b,'''

'''&c); '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The '''scanf''' statement takes input from the user for the variables '''a''', '''b''' and''' c'''.

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''if((a > b) && (a > c)) '''

'''printf("a is greatest \n"); '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here, We are comparing the values of '''a''' with '''b''' and '''c''' to find the greatest.

To compare simultaneously, we use the '''logical''' '''AND '''operator.

Here, all of the conditions have to be true for '''logical AND '''to return a true value.

The expression is not evaluated further on encountering a false condition.

So, the expression '''(a>c) '''is evaluated only if '''(a>b)''' is true.

If a is less than b, then the expression won't be evaluated further.

This statement is be evaluated if the previous condition is true. 

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''else if (b > c) '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Next '''(b>c) '''is evaluated.




|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''printf("b is greatest \n"); '''



| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| If the condition is true, then '''b is greatest''' is displayed on the screen.

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''else '''

'''printf("c is greatest \n");'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Otherwise '''c is greatest '''is displayed on the screen. 

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''if(a == 0 || b == 0 || c == 0) '''



| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We now come to the '''logical OR '''operator.

Here, any one of the conditions has to be true for '''logical OR '''to return a true value.

The expression is not evaluated further on encountering a true condition.

So, if '''a''' == zero, then the remaining two expressions won't be evaluated.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight''' '''


'''printf("The product of a, b'''

'''and c is zero \n"); '''



| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This '''printf''' statement is executed if either of '''a''', '''b''' or '''c''' is 0.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight


'''return 0; '''

'''} '''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Coming to the end of the program.

'''return 0''' and ending curly bracket.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Click on '''Save'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now save the program.

'''Save''' it with extension '''.c'''

I have saved my file as '''logical.c'''




|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| press '''Ctrl, Alt and T '''keys''' '''simultaneously.
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Open the terminal by pressing '''Ctrl, Alt and T '''keys simulataneously.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Type

'''gcc logical.c -o log'''

Type

'''./log'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To compile the code type

'''gcc logical.c -o log'''

For executing the code type

'''./log'''

Press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Output:
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here it is displayed as,

Enter the values of a,b and c 

I will enter the values as, 

0 

34 

567 

The output is displayed as,

c is greatest. 

The product of a, b and c is zero.

You should try executing this program with different sets of inputs.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let's write the same program in C++

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Open the C++ file.
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| I have already made the program and will take you through it.

Here is the code in '''C++'''.

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| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| //Logical operators in C++ 

<nowiki>#include <iostream> </nowiki>

using namespace std; 

int main() 

{ 

int a,b,c; 

<nowiki>cout <<"Enter the values of a,b</nowiki>

and c \n"; 

cin >>a >>b >>c; 

if((a > b) && (a > c)) 

<nowiki>cout <<"a is greatest \n"; </nowiki>

else if (b > c) 

<nowiki>cout <<"b is greatest \n"; </nowiki>

else 

<nowiki>cout <<"c is greatest \n"; </nowiki>

if(a == 0 || b == 0 || c == 0) 

<nowiki>cout <<"The product of a, b and</nowiki>

c is zero \n"; 

return 0; 

} 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now to make the same program in C++, we make a few changes.

There's a change in the header file.

Using statement has been used.

Also there is a difference in output and input statements.

The operators behave in the same way as they did in C.




|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Click on '''Save'''.

point to '''.cpp'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Click on '''Save'''.

Make sure the file is saved with extension '''.cpp'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| press '''Ctrl, Alt and T '''keys''' '''simultaneously.
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Open the terminal by pressing '''Ctrl, Alt and T '''keys simulataneously.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| On the terminal type 

'''g++ logical.cpp -o log'''

to execute

'''./log'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| To compile the program type

'''g++ logical.cpp -o log1'''

to execute the program type

'''./log1'''

press '''Enter.'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Output:
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Here it is displayed as,

Enter the values of a,b and c 

I will enter the values as

0 

34 

567 

We see the output is similar to the C program.

You should try executing the program with different sets of inputs too.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| '''Errors'''



| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now let us see an error which we can come across.

Let's switch to the editor.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Delete


'''if(a > b) && (a > c)'''



| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Suppose here we forgot the brackets.

Delete this and this.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let see what will happen

Come back to the terminal

Compile and execute as before

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Highlight '''Error'''
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| We see the error:

Expected identifier before '(' token.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is because we have two different expressions here

We have to evaluate them as one expression using AND operator.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Now let us go back to our program and fix the error

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us insert the brackets here and here. 

Click on '''Save'''

Come back to the terminal.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| 
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Let us compile and execute as before

So it is working now.

Let us now summarize the tutorial.

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Summary:
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| In this tutorial we learnt about the logical operators

&& Logical AND 

eg. '''((a > b) && (a > c)) '''


|| Logical OR

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




|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Assignment:
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Write a program that takes two numbers as input from the user.

Check whether the two numbers are equal or not using '''NOT''' operator.

Hint: '''(a != b)'''

|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 5

'''About the Spoken Tutorial Project''' 

* Watch the video available at [http://spoken-tutorial.org/What_is_a_Spoken_Tutorial http://spoken-tutorial.org/What_is_a_Spoken_Tutorial] 

* It summarises the Spoken Tutorial project 

* If you do not have good bandwidth, you can download and watch it 


| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| * Watch the video available at the following link 

* It summarises the Spoken Tutorial project 

* If you do not have good bandwidth, you can download and watch it 



|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 6

'''Spoken Tutorial Workshops''' 

The Spoken Tutorial Project Team 

* Conducts workshops using spoken tutorials 

* Gives certificates for those who pass an online test 

* For more details, please write to contact@spoken-tutorial.org 


| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| The Spoken Tutorial Project Team * Conducts workshops using spoken tutorials 

* Gives certificates for those who pass an online test 

* For more details, please write to contact at spoken hyphen tutorial dot org 



|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Slide 7

'''Acknowledgement''' 

* Spoken Tutorial Project is a part of the Talk to a Teacher project 

* It is supported by the National Mission on Education through ICT, MHRD, Government of India 

* More information on this Mission is available at 

* [http://spoken-tutorial.org/NMEICT-Intro http://spoken-tutorial.org/NMEICT-Intro] 


| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| Spoken Tutorial Project is a part of the Talk to a Teacher project * It is supported by the National Mission on Education through ICT, MHRD, Government of India 

* More information on this Mission is available at 

* spoken hyphen tutorial dot org slash NMEICT hyphen Intro 



|-
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:none;padding:0.097cm;"| Remain on previous slide

No slide for this part
| style="border-top:none;border-bottom:1pt solid #000000;border-left:1pt solid #000000;border-right:1pt solid #000000;padding:0.097cm;"| This is Ritwik Joshi from IIT Bombay. 

Thank you for joining. 

|}