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Logical Operators | Control Structures
C# Basics
course content

Course Content

C# Basics

C# Basics

1. Getting Started
2. Dealing with Data Types
3. Control Structures
4. Loops
5. Arrays
6. Methods

Logical Operators

Logical Operators can be used for combining two logical expressions or logical values. Following are the three logical operators:

OperatorOperation
&&AND
||OR
!NOT

Note

An operand refers to a value or expression that is used as an input for an operator in a statement or expression. For-example in the expression 1 + 2, the values 1 and 2 are operands. In the case of logical operators, an operand is always a boolean expression or value.

The AND (&&) operator takes two operands and returns true only if both the operands are true. It is demonstrated by the following code:

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using System; namespace ConsoleApp { internal class Program { static void Main(string[] args) { Console.WriteLine(true && true); // Output: True Console.WriteLine(true && false); // Output: False Console.WriteLine(false && true); // Output: False Console.WriteLine(false && false); // Output: False } } }

Instead of directly using the true and false literals (values), we commonly use expressions:

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using System; namespace ConsoleApp { internal class Program { static void Main(string[] args) { /* A program to check if the variable `value` is in the range specified by `range_start` and `range_end` variables.*/ int value = 7; int range_start = 0; int range_end = 10; Console.WriteLine(range_start < value && value < range_end); // Output: True } } }

The OR (||) operator returns true if any one of the operands is true:

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using System; namespace ConsoleApp { internal class Program { static void Main(string[] args) { Console.WriteLine(true || true); // Output: True Console.WriteLine(true || false); // Output: True Console.WriteLine(false || true); // Output: True Console.WriteLine(false || false); // Output: False } } }

Following is an example which uses the OR (||) operator:

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using System; namespace ConsoleApp { internal class Program { static void Main(string[] args) { int val1 = 5; int val2 = 7; int val3 = 9; Console.WriteLine(val2 > val1 || val2 > val3); // Output: True } } }

The NOT (!) operator simply negates (inverts) the logical expression or logical value. So if an expression returns true, it changes it into false.

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using System; namespace ConsoleApp { internal class Program { static void Main(string[] args) { Console.WriteLine(!true); // Output: False Console.WriteLine(!false); // Output: True // We need to enclose expressions in brackets () before negating them Console.WriteLine(!(5 < 0)); // Output: True Console.WriteLine(!(0 < 5 && 5 < 10)); // Output: False } } }

What is the expression (0 < 5 || 5 < 10) equal to?

Select the correct answer

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Section 3. Chapter 2
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