Logical operators in C

 Logical operators are used to perform logical AND, OR and NOT operations.  It is used to connect one or more relational/conditional expressions to form a complex logical expression.  Any expression that evaluates to 0 is considered to be false and any expression that evaluates to non-zero value is considered to be true.

Logical operator example in C:
int x = 10, y = 20;
if ((x > 10) && (y > 10) {  // checks whether both the expressions are true
  printf("x and y are greater than 10");
}

if ((x > 10) || (y > 10) {  // checks whether atleast any one of the expression is true
  printf("any one or both x & y are greater than 10");
}

if (!(x > 10)) { // checks whether x is not greater than 10
        printf("x is not greater than 10");
}

Logical operators in C:

Operator	Operation
&&	logical AND
||	logical OR
!	logical NOT

Below is the truth table for AND, OR and NOT logical operators.

Truth table for logical AND operator:

---

Operand1	Operand2	Result
False	False	False
False	True	False
True	False	False
True	True	True

Truth table for logical OR operator:

---

Operand1	Operand2	Result
False	False	False
False	True	True
True	False	True
True	True	True

Truth table for logical NOT operator:

---

Operand	Result
False	True
True	False

Example C program using Logical Operators:

 
  #include <stdio.h>
  int main() {
        int a, b;
        printf("Enter two number: ");
        scanf("%d%d", &a, &b);
        if ((a > 100)  && (b > 100)) {
                printf("Both %d and %d are greater than 100\n", a, b);
                printf("Assigning 50 t0 b\n");
                b = 50;
        }

        if ((b > 100) || (a > 100)) {
                printf("\nHitting Logical OR\n");
                printf("%d is greater than 100\n\n", a);
        }

        if (!(b > 100)) {
                printf("%d is not greater than 100\n", b);
                printf("Hitting Logical NOT\n");
        }
        return 0;
  }

  Output:

  jp@jp-VirtualBox:~/$ ./a.out
  Enter two number: 101 200
  Both 101 and 200 are greater than 100
  Assigning 50 t0 b

  Hitting Logical OR
  101 is greater than 100

  50 is not greater than 100
  Hitting Logical NOT