Logical Operators in C Language


Operators Definition

As studied earlier, Operators are the symbols, which performs operations on various data items known as operands. For Example: in a a+b, a and b are operands and + is an operator.

Note:- To perform an operation, operators and operands are combined together forming an expression. For example, to perform an addition operation on operands a and b, the addition(+) operator is combined with the operands a and b forming an expression.

Logical Operators

Logical operator is used to find out the relationship between two or more relationship expressions.

The C language logical operators allow a programmer to combine simple relational expression to form complex expressions by using logical not, and and or.

Operator Description Example
&& Logical AND operator. If both the operands are non-zero, then the condition becomes true. (A && B) is false.
|| Logical OROperator. If any of the two operands is non-zero, then the condition becomes true. (A || B) is true.
! Logical NOT Operator. It is used to reverse the logical state of its operand. If a condition is true, then Logical NOT operator will make it false. !(A && B) is true.

Taking the logical And, when two expressions are added the resulting expression will be true only if both of the sub-expressions are true. Eg, (X>5) && (Y<15) will be only true if x greater than 5 and if y is less than 15. The second expression (Y,15) will not be evaluated if the first expression is false.

A logical expression is evaluated from left to right as far as needed to determine the logical result. Eg. in the expression (Y<15)&&(X++>15), the value of X is incremented only if the value of Y is less than 15.

The logical or is represented by two vertical bars between two other expression as expression1 || expression2. The logical result of the entire expression will be true if either of the two expression surrounding the || is logically true. Expression involving the logical or are evaluated from left to right only when the result of the logical expression is known.



 Line 1 - Condition is true
 Line 2 - Condition is true
 Line 3 - Condition is not true
 Line 4 - Condition is true

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