Logical Operators In C

Logical Operators in C programming language return true(non-zero number) or false(0) value. Logical AND(&&) and logical OR(||) works on 2 operands. But logical NOT(!) works on single operand.

Related Read:
Relational Operators In C

Logical Operators

&& – Logical AND Operator.
|| – Logical OR Operator.
! – Logical NOT Operator.

&& – Logical AND Operator.

 
#include < stdio.h >

int main()
{
    int a;

    a = ( 1 && 1 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 1

 
#include < stdio.h >

int main()
{
    int a;

    a = ( 0 && 1 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 0

For logical AND(&&) both operands or expressions must yield to true. If any one condition is false(0), then it’ll return false(0).

|| – Logical OR Operator.

 
#include < stdio.h >
int main()
{
    int a;

    a = ( 1 || 1 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 1

 
#include < stdio.h >
int main()
{
    int a;

    a = ( 1 || 0 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 1

 
#include < stdio.h >
int main()
{
    int a;

    a = ( 0 || 0 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 0

Logical OR(||) returns true(any non-zero number) if either one condition/operand is true. It returns false(0) only when both the conditions / operands are false(0).

! – Logical NOT Operator.

 
#include < stdio.h >
int main()
{
    int a;

    a = ( !1 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 0

 
#include < stdio.h >
int main()
{
    int a;

    a = ( !0 );

    printf("value of a is %d\n", a);

    return 0;
}

Output:
value of a is 1

Logical NOT(!) returns true if the condition is false. It returns false if the condition is true. It just negates the Boolean value given to it.

Logical Operators In C

Logical Operators combined with Relational Operators

&& – Logical AND Operator.

 
#include < stdio.h >

int main()
{
    int a, b = 100;

    a = ( (b == 0) && (b > 50) );

    printf("Value of a is %d\n", a);

    return 0;
}

Output:
value of a is 1

a is true because both b is equal to 100 is true and b is greater than 50 is true.

 
#include < stdio.h >

int main()
{
    int a, b = 100;

    a = ( (b == 0) && (b > 150) );

    printf("Value of a is %d\n", a);

    return 0;
}

Output:
value of a is 0

a is false(0) because b is equal to 100 is true but b is greater than 150 is false.

|| – Logical OR Operator.

 
#include < stdio.h >

int main()
{
    int a, b = 100;

    a = ( (b == 0) || (b > 50) );

    printf("%d\n", a);

    return 0;
}

Output:
value of a is 1

Value of a is true, because b is equal to true. In logical OR(||) if one condition is true, then it returns true. It returns false(0) only when both the conditions / operands are false(0).

! – Logical NOT Operator.

 
#include < stdio.h >

int main()
{
    int a, b = 100;

    a = ( !(b == 0) );

    printf("%d\n", a);

    return 0;
}

Output:
value of a is 0

Value of a is false(0). Because b is equal to 100 is true. When true value is given to NOT(!) it’ll return false(0). When false value is supplied to NOT it’ll return true.

Note: = is assignment operator. == is equality operator.

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