# Logical Operators in C

Logical operators are used to perform logical operations of given expressions (relational expressions) or variables.

There are three logical operators available in C. Letâ€™s discuss one by one.

## || (Logical OR) operator

If one of the operands or expressions is true, it will return 1.

If all of them are false, it will return 0.

A |
B |
A || B |
Example |
---|---|---|---|

0 |
0 |
0 |
(5 > 10) || (5 < 4) Both expressions are false. so, logical OR output will be 0 |

0 |
1 |
1 |
(10 > 20) || (10 < 20) First expression is false and second one is true. so, logical OR output will be 1 |

1 |
0 |
1 |
(10 < 20) || (10 > 100) First expression is true and second one is false. so, logical OR output will be 1 |

1 |
1 |
1 |
(10 < 20) || (10 < 100) Both expressions are true. so, logical OR output will be 1 |

## && (Logical AND) operator

If both left and right operands or expressions are true, it will return true. Otherwise, it will return false.

Note, non-zero value operands are considered as true.

A |
B |
A && B |
Example |
---|---|---|---|

0 |
0 |
0 |
(5 > 10) && (5 < 4) Both expressions are false. so, logical AND output will be 0 |

0 |
1 |
0 |
(10 > 20) && (10 < 20) First expression is false and second one is true. so, logical AND output will be 0 |

1 |
0 |
0 |
(10 < 20) && (10 > 100) First expression is true and second one is false. so, logical AND output will be 0 |

1 |
1 |
1 |
(10 < 20) && (10 < 100) Both expressions are true. so, logical AND output will be 1 |

## ! (Logical NOT) operator

Logical NOT operator is used to inverse the current decision. Say, if current state is true, Logical NOT (!) operator will make it false.

A |
!A |
Example |
---|---|---|

0 |
1 |
!(100 < 10) 100 is greater than 10. So, it will return false. |

1 |
0 |
!(10 < 100) 10 is less than 100. So, it will return true. |

## Sample Program

Example

#include<stdio.h> int main() { int a = 5, b = 10 ,ret; ret = ( (a <= b) || (a != b) ); // 5 <= 10 ==> true. 5 != 10 ==> true. So, 1 || 1 will return 1. printf("Return value of above expression is %d\n",ret); ret = ( ( a < b) && (a == b ) ); // 5 < 10 ==>true. 5 == 10 ==> false. So, 1 && 0 will return 0; printf("Return value of above expression is %d\n",ret); ret = ! ( ( a < b) && (a == b ) ); /*we have used the same expression here. And its result was 0. So !0 will be 1.*/ printf("Return value of above expression is %d\n",ret); return 0; }