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Logical Operators in C with Examples

 Program Abstraction:   This C programming tutorial describes the concept of Logical Operators with examples

Logical operators are the operators using for logical operations. They are 3 types:



  1. &&     (Logical AND) 
  2.   ||        (Logical OR) 
  3.   !        (Logical NOT) 

1. && (Logical AND)

         In C, this operator using instead of the word ‘and’ in English. Let us see an example:
‘If I am a writer and you are a reader then let us sign a song’. 


Here we will sing if and only if I am a writer and you are reader, otherwise not. Here the and denotes the logical AND.

Let us see an example in C:  A program than accept two numbers. If first number is smaller than 10 and second number is larger than 10, then display ‘Thanks’

  #include<stdio.h>
 #include<conio.h>
void main()
{
int a, b;

    clrscr();
    printf(“Enter the first number ”);
scanf(“%d”,&a);
printf(“nEnter the second number ”);
scanf(“%d”,&b);
if(a<10 && b>10)
{
printf(“Thanks”);
}
getch();
}

(a<10 && b>10) 

In this line, if a (first number) is less than 10 and (second number) is greater than 10, then the program will display ‘Thanks’. That is, if the both condition is true, then program will display ‘Thanks’, If any one of condition is true, then program will not display ‘Thanks’.
Sample Output:
Logical AND operator in C

Another Example: If both two numbers are greater than 10, then display the sum of two numbers

 #include<stdio.h>

 #include<conio.h>
void main()
{
int a, b;
printf(“Enter the first number”);
scanf(“%d”,&a);
printf(“nEnter the second number”);
scanf(“%d”,&b);
if( (a && b) > 10)
{
printf(“%d”, a+b);
}
getch();
}

Sample Inputs and Outputs

  a   b  Output
    5    15  Thanks
    7     9  no output
   12    23  no output
   10    10  no output
   -11    500  Thanks

2. || (Logical OR)

Implementing of Logical OR is same as Logical AND, but working is not same. Here if anyone of conditions is true, then program block will work. No need to satisfy both condition like Logical AND.

Example: If I am a driver or you are a driver, then let us go to the Park. Here, no need to both are driver to go to the Park.

Example with C: Accept two number, if first number is less than 25 or second number is greater than 25, then display their sum.

 #include<stdio.h>
#include<conio.h>
void main()
{
int a, b;
printf(“Enter the first number”);
scanf(“%d”,&a);
printf(“nEnter the second number”);
scanf(“%d”,&b);
if(a <25 || b > 25)
{
printf(“%d”, a+b);
}
getch();
}

Here no need to satisfy both condition to display their sum.

Sample Output:

Sample Inputs and Outputs

  a   b  Output
    20     30     50
    10     23     33
    28     52     80
    25     25  no output
    35     14  no output

3. ! (Logical NOT)

Not is the just complimentary of any condition or statement.

Example: if he is not a singer, then I will sing a song.
Here if he is a singer, then I can’t sing. So if I have to sing a song, he should not be a singer.

Example in C:  Accept two numbers, if the sum of them is not greater than 20, then display their sum

 #include<stdio.h>
#include<conio.h>
void main()
{
int a, b;
printf(“Enter two numbers”);
scanf(“%d%d”,&a,&b);
if (!((a+b)>20))
{
printf(“%d”, a+b);
}
getch();
}

Sum will display if and only if their sum is less than 20.  

Sample Output:

Sample Inputs and Outputs

  a b  Output
     8     8      16
    10     9      19
     1    16      17
    10    10  no output
    15    15  no output

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