# What Is Application of Queue in Data Structure?

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Scott Campbell

In data structures, a queue is an abstract data type that follows the FIFO (First In, First Out) principle. It is a linear data structure that represents a collection of elements where the addition of new elements happens at one end, known as the rear, and the removal of existing elements occurs at the other end, known as the front. This article will explore the application of queues in various scenarios and how they can be implemented using different programming languages.

## Applications of Queue Data Structure:

A queue data structure finds its application in several real-life scenarios. Let’s explore some common use cases:

### 1. Job Scheduling:

In operating systems, queues are used to schedule processes or jobs.

The jobs are added to the queue and get executed in the order they arrive. This ensures fairness and prevents any single job from monopolizing system resources.

### 2. Printer Spooler:

A printer spooler uses a queue to manage print jobs.

When multiple users send print requests simultaneously, each request gets added to the queue. The printer then processes them one by one in the order they were received.

### 3. Breadth-First Search (BFS) Algorithm:

In graph theory, BFS is an algorithm that explores all vertices of a graph in breadth-first order. A queue is used to keep track of visited nodes and manage the order in which vertices are processed.

### 4. CPU Scheduling:

In computer architecture, queues play a crucial role in scheduling processes for execution on a CPU. Different algorithms like Round Robin, First-Come-First-Serve (FCFS), and Shortest Job Next (SJN) use queues to manage the execution order of processes.

## Implementing a Queue in Programming:

Queues can be implemented using various programming languages. Let’s take a look at a basic implementation in Python:

``````
class Queue:
def __init__(self):
self.queue = []

def enqueue(self, item):
self.queue.append(item)

def dequeue(self):
if not self.is_empty():
return self.pop(0)

def is_empty(self):
return len(self.queue) == 0

def size(self):
return len(self.queue)
```
```

This implementation uses a list as the underlying data structure. The `enqueue()` function adds elements to the rear of the queue, while the `dequeue()` function removes elements from the front. The `is_empty()` function checks whether the queue is empty or not, and the `size()` function returns the current size of the queue.

### Conclusion:

A queue data structure is a fundamental concept in computer science and finds application in various scenarios such as job scheduling, printer spooling, graph algorithms, and CPU scheduling. Understanding queues and their implementations is essential for designing efficient algorithms and managing data effectively.

To recap, we explored different applications of queues and saw how they can be implemented using Python. Now that you have a better understanding of queues, you can apply this knowledge to solve problems that require FIFO behavior.