C++ Logical Operators for beginner to expert

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Logical operators are used to check whether an expression is true or false. If the expression is true, it returns 1 whereas if the expression is false, it returns 0.

Operator	Example	Meaning
`&&`	expression1 && expression2	Logical AND. True only if all the operands are true.
`\|\|`	expression1 \|\| expression2	Logical OR. True if at least one of the operands is true.
`!`	!expression	Logical NOT. True only if the operand is false.

In C++, logical operators are commonly used in decision making. To further understand the logical operators, let’s see the following examples,

Suppose,
a = 5
b = 8

Then,

(a > 3) && (b > 5) evaluates to true
(a > 3)  && (b < 5) evaluates to false

(a > 3) || (b > 5) evaluates to true
(a > 3) || (b < 5) evaluates to true
(a < 3) || (b < 5) evaluates to false

!(a < 3) evaluates to true
!(a > 3) evaluates to false

Example: Logical Operators

#include <iostream>
using namespace std;

int main() {
    bool result;

    result = (3 != 5) && (3 < 5);     // true
    cout << "(3 != 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 < 5);    // false
    cout << "(3 == 5) && (3 < 5) is " << result << endl;

    result = (3 == 5) && (3 > 5);    // false
    cout << "(3 == 5) && (3 > 5) is " << result << endl;

    result = (3 != 5) || (3 < 5);    // true
    cout << "(3 != 5) || (3 < 5) is " << result << endl;

    result = (3 != 5) || (3 > 5);    // true
    cout << "(3 != 5) || (3 > 5) is " << result << endl;

    result = (3 == 5) || (3 > 5);    // false
    cout << "(3 == 5) || (3 > 5) is " << result << endl;

    result = !(5 == 2);    // true
    cout << "!(5 == 2) is " << result << endl;

    result = !(5 == 5);    // false
    cout << "!(5 == 5) is " << result << endl;

    return 0;
};

Output

(3 != 5) && (3 < 5) is 1
(3 == 5) && (3 < 5) is 0
(3 == 5) && (3 > 5) is 0
(3 != 5) || (3 < 5) is 1
(3 != 5) || (3 > 5) is 1
(3 == 5) || (3 > 5) is 0
!(5 == 2) is 1
!(5 == 5) is 0

Explanation of logical operator program

(3 != 5) && (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
(3 == 5) && (3 < 5) evaluates to 0 because the operand (3 == 5) is 0 (false).
(3 == 5) && (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
(3 != 5) || (3 < 5) evaluates to 1 because both operands (3 != 5) and (3 < 5) are 1 (true).
(3 != 5) || (3 > 5) evaluates to 1 because the operand (3 != 5) is 1 (true).
(3 == 5) || (3 > 5) evaluates to 0 because both operands (3 == 5) and (3 > 5) are 0 (false).
!(5 == 2) evaluates to 1 because the operand (5 == 2) is 0 (false).
!(5 == 5) evaluates to 0 because the operand (5 == 5) is 1 (true).