Logical Operators

Logical operators in C

Logical operators in C are used to perform logical operations on the given expressions and to combine multiple conditions/constraints, Returns either 0 or 1, it depends on the expression result true or false.

The following are the logical operators in C:

&& (logical AND):

• This operator returns 1 if both expressions are true or non zero , otherwise it returns 0.
• The syntax for the && operator is as follows:

if (expression1 && expression2)
{
   // code to be executed if both expressions are true
}

Expression1	Expression2	Expression1 && Expression2
true	true	(1) true
true	false	(0) false
false	true	(0) false
false	false	(0) false

|| (logical OR)

• This operator returns 1 if either of the expressions is true or non zero , otherwise it returns 0.
• The syntax for the || operator is as follows:

if (expression1 || expression2)
{
   // code to be executed if either of the expressions is true
}

Expression1	Expression2	Expression1 || Expression2
true	true	(1) true
true	false	(1) true
false	true	(1) true
false	false	(0) false

! (logical NOT)

• This operator returns 1 if the expression is false or zero, otherwise it returns 0.
• The syntax for the ! operator is as follows:

if (!expression)
{
   // code to be executed if the expression is false
}

Expression	!Expression
true	(0) false
false	(1) ture

Example of Logical operators in C

#include <stdio.h>

int main()
{
    int x = 5, y = 10;

    // using && (logical AND) operator
    if (x < 10 && y > 5)
    {
        printf("x is less than 10 and y is greater than 5\n");
    }
    else
    {
        printf("x is not less than 10 or y is not greater than 5\n");
    }

    // using || (logical OR) operator
    if (x == 5 || y == 8)
    {
        printf("x is equal to 5 or y is equal to 8\n");
    }
    else
    {
        printf("x is not equal to 5 and y is not equal to 8\n");
    }

    // using ! (logical NOT) operator
    if (!(x == y))
    {
        printf("x is not equal to y\n");
    }
    else
    {
        printf("x is equal to y\n");
    }

    return 0;
}

Output:

Output:

x is less than 10 and y is greater than 5
x is equal to 5 or y is equal to 8
x is not equal to y

note

In C, any non-zero value is considered true, and 0 is considered false.

Practical use cases of Logical operators

Here are some practical use cases of logical operators in C:

Conditional statements

Logical operators are often used in conditional statements such as if-else, switch-case, and loops to check multiple conditions and execute different code based on the results.

Example:

if (x == 5 && y == 10)
{
    printf("x is equal to 5 and y is equal to 10\n");
}

Input validation

Logical operators can be used to validate user input to ensure that the input is within a specified range or meets certain criteria.

Example:

if (age >= 18 || age <= 30)
{
    printf("You are eligible to participate in the survey\n");
}

Error handling

Logical operators can be used to check for errors or exceptional conditions in a program and handle them appropriately.

Example:

if (!file_pointer)
{
    printf("Error: Unable to open file\n");
}

Combining multiple conditions

Logical operators can be used to combine multiple conditions to check if all or any of the conditions are true and take appropriate action.

Example:

if (x > 10 || y < 20 || z == 30)
{
    printf("At least one of the conditions is true\n");
}