This document discusses logical operators in C#. It defines logical operators as allowing you to combine multiple conditions and describes the AND, OR, NOT, and XOR logical operators. It provides truth tables for each operator and examples of how each operator is used in programming code to evaluate Boolean expressions.

1. Logical Operators
ICT Level V
COT - Jaffna
1
S.Sakthybaalan

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Operator
 An operator is a symbol that tells the compiler to perform specific
mathematical or logical manipulations.
 C# is rich in built-in operators and provides the following kinds of
operators:
 Arithmetic Operators
 Relational Operators
 Logical Operators
 Bitwise Operators
 Assignment Operators
 Misc Operators

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Operators
Arithmetic Operators
Relational Operators
Bitwise Operators
Assignment Operators
Misc Operators
Logical Operators

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Logical Operators (Conditional
Operators)
 Logical operators allows you to combine multiple conditions.
 These operators involves at least two conditions and the final
Boolean result is determined by the operator being used.
AND
OR
XOR
NOT
Logical Operators

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Operand and Operators
 In all computer languages, expressions consist of two types of
components: operands and operators.
 Operands are the objects that are manipulated.
 Operators are the symbols that represent specific actions.
 example:
5 + x
 Note:
 All expressions have at least one operand.
operator
operands

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AND Operator (&&)
 The AND operator is used to compare two Boolean values.
 It returns true if both of the operands are true.
a b Result (AND)
0 0 0
0 1 0
1 0 0
1 1 1
0 – false
1 - true

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AND Operator in Programming
name = "Steven";
password = "Steven123";
// evaluating both expression and returns true if all are true.
if (name == "Steven" && password == "Steven123")
{
MessageBox.Show("Login Successful");
}
else
{
MessageBox.Show "Unauthorised access");
}

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OR Operator (||)
 The OR operator is similar to AND, as it is used to compare two
Boolean values.
 The OR operator returns true if either of the operand(s) are true.
a b Result (OR)
0 0 0
0 1 1
1 0 1
1 1 1
}
0 – false
1 - true

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OR Operator in Programming
string username, password;
if ((username == "Steven" || username == “Clark")
&& (password == "Steven123"))
{
MessageBox.Show("Login Successful");
}
else
{
MessageBox.Show("Unauthorised access");
}

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NOT Operator (!)
 The NOT operator is a unary operator, as it operates on a single
operand.
 The NOT operator inverts the value of a Boolean value.
 If the original value is true then the returned value is false; if the
original value is false, the return value is true.
a Result (NOT)
0 1
1 0
0 – false
1 - true

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NOT Operator in Programming
name = "Steven";
password = "Steven123";
// evaluating both expression and returns true if all are true.
if ( !(name == "Steven" && password == "Steven123"))
{
MessageBox.Show("Login Successful");
}
else
{
MessageBox.Show("Unauthorised access. Aborting…");
}

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XOR Operator (^)
 It returns false if the following condition matches:
 (i) if both or all the expression returns true.
 (ii) If both or all the expression returns false.
a b Result (XOR)
0 0 0
0 1 1
1 0 1
1 1 0
0 – false
1 - true

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XOR Operator in Programming
string name, password;
name = "Steven" ;
password = "Steven123" ;
//it returns false because both expression match.
if ((name == "Steven" ^ password == “Clark")
{
MessageBox.Show(“Access granted…");
}
else
{
MessageBox.Show (“Access Denied. Aborting…”);
}

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