A logical operator is used to compare or evaluate logical and relational expressions. There are three logical operators in C Plus Plus (C++) language. They are:

Operator | Meaning |
---|---|

&& | Logical AND |

|| | Logical OR |

! | Logical NOT |

An expression involving && or || is sometimes called **compound expressions**, since the expression involves two other expressions, that is, each of these operators (&& and ||) takes two expressions, one to the left and another to the right.

**Example of && operator:**

Consider the following expression:

1 |
a > b && x == 10 |

The expression on the left is `a > b`

and that on the right is `x == 10`

. The above stated whole expression evaluates to **true** (1) only if both the expressions are true (i.e., if `a`

is greater than `b`

and the value of `x`

is equal to 10).

**Example of || operator:**

Consider the following expression:

1 |
a < m || a < n |

The above expression is true if one of the expression (either `a < m`

or `a < n`

) is **true**. That is, if the value of `a`

is less than that of `m`

or `n`

then the whole expression evaluates to **true**. Needless to say, it evaluates to **true** in case `a`

is less than both `m`

and `n`

.

**Example of ! operator:**

The ! (NOT) operator takes single expression and evaluates to **true** (1) if the expression is **false** (0), and evaluates to **false** (0) if the expression is **true** (1). In other words, it just reverses the value of the expression.

For example, consider the following expression:

1 |
!(x >= y) |

The expression after the ! operator is `x >= y`

. The above **not** expression evaluates to true only if the value of `x`

is neither greater than nor equal to `y`

(i.e., only if `x`

is less than `y`

). Therefore, the whole expression including the ! operator is the same as:

1 |
x < y |

**Precedence of Logical Operators:**

Each of the logical operators falls into its own precedence group. All precedence groups are lower than the group containing the equality operators. The associativity is **left to right**.