## 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

A | B | Output (O) |

0 | 0 | 1 |

0 | 1 | 0 |

1 | 0 | 0 |

1 | 1 | 1 |

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

if(A == B): output = 1 else: output = 0This 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 |

### 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 |

### 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 = FALSEThis 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.

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