What Is Queue in the Data Structure?


Scott Campbell

A queue is a fundamental data structure in computer science that follows the First-In-First-Out (FIFO) principle. It is similar to a real-life queue, where the person who arrives first is the first one to be served. In this article, we will explore the concept of a queue and its implementation in programming.

A queue is an ordered collection of elements in which an element is inserted at one end, called the rear, and removed from the other end, called the front. The rear position is also known as “enqueue,” while removing from the front position is called “dequeue.”

The Basic Operations of a Queue:

  • Enqueue: This operation adds an element to the rear of the queue.
  • Dequeue: This operation removes and returns the element from the front of the queue.
  • IsEmpty: This operation checks if the queue is empty. If there are no elements in the queue, it returns true; otherwise, it returns false.
  • Size: This operation returns the number of elements present in the queue.

The Advantages of Using a Queue:

  • A queue allows efficient insertion at one end and deletion at another end.
  • FIFO order makes queues suitable for scenarios like printing documents or processing tasks in order.
  • A bounded-size queue can be used to implement a buffer or limit resource usage.

The Disadvantages of Using a Queue:

  • Accessing elements in positions other than front or rear may not be efficient.
  • Queues have a fixed size in some programming languages, which can lead to overflow or underflow situations.

Implementing a Queue:

To implement a queue, we can use various programming languages such as C++, Java, Python, or JavaScript. Here’s an example of implementing a queue using an array in Python:

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

def enqueue(self, item):

def dequeue(self):
if not self.is_empty():
return self.pop(0)
return “Queue is empty.”

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

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

In this example, we use a Python list to store the elements of the queue. The `enqueue` function appends an item to the end of the list, while the `dequeue` function removes and returns the first item from the list using the `pop(0)` method. The `is_empty` function checks if the queue is empty by checking its length, and the `size` function returns the number of elements present in the queue.


A queue is a simple yet powerful data structure that follows the FIFO principle. It finds applications in various fields like operating systems, network routing algorithms, and simulation systems. Understanding and implementing queues can enhance your problem-solving skills and enable you to design efficient algorithms.

Next time you encounter a situation where you need to maintain order and process elements in a specific sequence, consider using a queue data structure!

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