Relational and Logical Operators

Logical Operators

C++ supports three logical operators and the term logical refers to the ways these relationships can be connected. Here these relationships refer to the relations supported by the relational operator between two operands. Because, relational and logical operator often works together and it is also explained together here. The list of logical operators with their action is listed in the Table.

Working Process of Relational and Logical Operators

Both these sets of operators work with the idea of a relationship between two values either is true and false. In C/C++, any value other than zero is considered as true value and zero is considered as false. Consider the relationships listed in the Table, to understand the true and false relationship.

In C++ and since C99, defines a separate data type bool to handle zero/non-zero concept of true and false. The bool data type has two Boolean constants as true and false. In C++, a non-zero value automatically converts to true, and a zero value automatically converts to false. Consider the example metioned below (edit and try online):

bool check;

check = 4;

cout<<std::boolalpha;

cout<<check<<endl;

check = 0;

cout<<check;

In the above code, check is declared as bool data type, which can have only two values either as true or false. Thereafter, a non-zero value 4 is assigned to check and C++ compiler automatically converts 4 to true and assigned to check. To print any bool values we further need a manipulator boolalpha with cout stream object. Else all bool types will be displayed as 1 or 0. After setting a format flag to cout with insertion operator<<, the cout statement prints the value of check as true (as we have set it to 4). Thereafter, a zero value is assigned to check and cout prints the value of check as false.

Understanding Logical Operators with truth table

Lets consider the below statements

int p = 5>6;

int q = 5<6;

The expression 5>6 is a false relation between 5 and 6, so a value 0 is assigned to p. On the other hand, the expression 5<6 is a true relation between 5 and 6, so 1 as non-zero value is assigned to q. Let's print the truth table for the logical operators is displayed in the table using 1's and 0's.

Operator Precedence

Both the relational and logical operators are lower in precedence than the arithmetic operators. Let's consider the below expression

int k = 10 > 1+2;

as same as

int k = 10> (1+2);

The result of above expression is false, because 10>3 is a false relation. Let's prints the precedence and associativity table by combining arithmetic, relational, and logical operators together.