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XNOR Gate

Delve into the intricacies of the XNOR Gate, a fundamental concept in Computer Science. Understanding the XNOR Gate is key to grasping more complex digital logic and circuit designs. In this detailed study, you'll explore its definition, operation, boolean expressions, and truth table. The article also offers insights into the functionality of a 3 input XNOR Gate and its practical examples. Enhance your knowledge and explore the world of Computer Science with clarity and precision.

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XNOR Gate

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Delve into the intricacies of the XNOR Gate, a fundamental concept in Computer Science. Understanding the XNOR Gate is key to grasping more complex digital logic and circuit designs. In this detailed study, you'll explore its definition, operation, boolean expressions, and truth table. The article also offers insights into the functionality of a 3 input XNOR Gate and its practical examples. Enhance your knowledge and explore the world of Computer Science with clarity and precision.

Understanding the XNOR Gate

What is an XNOR Gate: XNOR Gate Definition

In the field of Computer Science and DIGITAL LOGIC, one of the most common components you will encounter is the XNOR gate, also known as 'equivalence gate'.

An XNOR gate (denoted as XNOR) is a digital logic gate that outputs true or '1' only when the number of true inputs is even. This peculiar ability makes it essential in certain circuits. The name "XNOR" is a portmanteau of XOR (which signifies 'exclusive OR') and NOT, reflecting the fact that its output is the inverse or 'NOT' of that of an XOR gate.

Exploring the XNOR Gate Operation

At the heart of the XNOR gate's operation lies the combination of different basic logic gates such as, OR, AND, and NOT gates. The way XNOR gate operates can be described by the Boolean Expression $$A' B + AB'$$. In the above expression,:
• $$A'$$ represents NOT A
• $$B'$$ represents NOT B
• $$+$$ is the Boolean OR operation
Now, let's examine the truth table for XNOR gate operation.
 A B Output (O) 0 0 1 0 1 0 1 0 0 1 1 1
From the Truth table, it is clear that the output is 'true' or '1' only when both inputs are the same, whether they be 0 or 1. This why XNOR is also often referred to as the 'equivalence gate'.
    if(A == B):
output = 1
else:
output = 0


Despite appearing similar to the XOR gate, the XNOR gate holds its own unique place in computer science and digital logic design. It is essential in circuits needing parity checking and equal detection functionality.

XNOR Gate: How it Functions

This segment will delve deeper into the working principle behind the XNOR gate. Remember, the XNOR gate, also known as the equivalence gate, is unique as it yields a high output (1) only when the input values are equal. It's important to bear in mind that it combines multiple Basic Logic Gates - AND, OR, and NOT gates, to carry out its operation.

How does an XNOR Gate Work?

To better understand the functioning of an XNOR gate, let's first recall that it outputs 'true' or '1' only when the number of true inputs is even. Consider a practical scenario with two switches A and B, connected to a light bulb through an XNOR gate. The light bulb will only light up when both switches are at the same position (both ON or both OFF). When the positions differ (one is ON and the other is OFF or vice versa), the light bulb remains off. This behaviour can be represented in a truth table. The truth table is a fundamental concept that helps in understanding the functioning of logic gates. Table for XNOR gate operation:
 A B Output (O) 0 0 1 0 1 0 1 0 0 1 1 1

Insights into the XNOR Gate Boolean Expression

The XNOR gate operation can be further elaborated with the help of its Boolean expression. The Boolean expression for the XNOR gate is $$AB + A'B'$$. Let's break it down:
• $$AB$$ stands for A AND B, meaning both A and B are 1
• $$A'B'$$ means A NOR B, meaning both A and B are 0
• The '+' in between represents the OR operation
So, according to this Boolean expression, the output is true or '1' when either both A and B are true or when they are both false. This is in sync with the XNOR gate's operation that it results in a '1' when the inputs are equal. One could represent this operation in computer code as well:
    if(A == B):
output = 1
else:
output = 0

This segment provides a deep understanding of the functions of an XNOR gate, from its practical applications to Boolean expression. Regardless of how advanced the digital circuit is, this very logic forms the core of digital operations and computing.

Diving Deeper into the XNOR Gate

As you delve further into the realm of digital logic and computer science, the XNOR gate is an elementary yet crucial concept to comprehend. With its unique properties and functions, it serves as a cornerstone for more complex electronic logic systems and circuits.

Decoding the XNOR Gate Truth Table

The truth table is an essential tool for understanding the functionality of a logic gate. By listing all possible input combinations alongside their respective output, the truth table for an XNOR gate provides a comprehensive view of its operation. An important aspect to note about the XNOR gate is that it gives a high output ('1') when the number of high inputs is even. The Truth table for XNOR gate is as follows:
 Input A Input B Output O 0 0 1 0 1 0 1 0 0 1 1 1
From the table, it is evident that the output is '1' when both inputs are the same, that is, either both 0 or both 1, hence the name "equivalence gate".

Grasping the Concept of a 3 Input XNOR Gate

So far, we’ve discussed the functionality of a 2-input XNOR gate. But what happens when there are three inputs? The principle remains the same: the XNOR gate yields a high output ('1') when the number of high inputs is even. Here is the truth table for a 3-input XNOR gate:
 Input A Input B Input C Output O 0 0 0 1 0 0 1 0 0 1 1 1 1 1 1 1
As can be seen, the output is '1' when there are even 'true' or '1' inputs.

Practical XNOR Gate Examples in Computer Science

It’s always helpful to grasp the practical implications of theoretical concepts. In the world of computer science, XNOR gates play an important role in parity generators and checkers, which are vital for error detection in digital communication and storage systems. It is also famously used in digital applications where unary operations are required. An excellent example that applies the XNOR gate involves the creation of a unary operation, bitwise equivalence checker. Given an array of boolean values, the operation determines if an even number of TRUE values exists within the array:
Array = [TRUE, FALSE, TRUE, TRUE, FALSE]
counter = 0

for i in Array:
if(i):
counter+=1

if(counter % 2 == 0):
output = TRUE
else:
output = FALSE

This operation essentially works as an XNOR gate over the array of boolean values, illustrating a unique and practical application of the XNOR gate concept.

XNOR Gate - Key takeaways

• The XNOR gate is a fundamental concept in Computer Science and digital logic, also known as 'equivalence gate'.
• An XNOR gate outputs true or '1' only when the number of true inputs is even, its output is the inverse of an XOR gate.
• The operation of an XNOR gate can be described by the Boolean expression $$A' B + AB'$$, expressing the combination of NOT, AND and OR operations.
• The XNOR gate's truth table makes clear that the output is 'true' or '1' only when both inputs are the same, hence the term 'equivalence gate'.
• A 3 input XNOR Gate yields a high output ('1') when the number of high inputs is even, while practical examples of XNOR gates can be found in parity generators and checkers, and unary operations in digital applications.

An XNOR gate, in computer science, is a gate that outputs true or '1' only when the number of true inputs is even. This is used in digital electronics to carry out logical equality, essentially determining if the number of true inputs matches the expected values.
An XNOR gate, in a digital logic circuit, operates by producing an output that's true or '1' only when the number of true inputs is even. In a two-input gate, the output is true if both inputs are the same (either both true or both false).
The truth table of an XNOR gate is: 0 XNOR 0 = 1, 0 XNOR 1 = 0, 1 XNOR 0 = 0, 1 XNOR 1 = 1. The Boolean expression for XNOR is A' B + A B', where A and B are inputs.
The main difference between XOR and XNOR gates in computing logic is their output. An XOR gate produces a high output (1) if the number of high inputs (1s) is odd. On the other hand, an XNOR gate produces a high output (1) if the number of high inputs (1s) is even.
An XNOR gate can be constructed with a combination of AND, OR, and NOT gates. For two inputs (A and B), you would use two NOT gates for the individual inputs, two AND gates for the combination of original and negated inputs, and then an OR gate combining the outputs of the AND gates.

Test your knowledge with multiple choice flashcards

What is an XNOR gate in digital logic?

What is the Boolean expression for the operation of the XNOR gate?

When does an XNOR gate output '1' or true?

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