What Are Queue in Data Structure?


Angela Bailey

A queue is a frequently used data structure in computer science that follows the FIFO (First In, First Out) principle. It is an abstract data type 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.” In simple terms, a queue can be visualized as a line of people waiting for their turn.

Basic Operations in a Queue:

  • Enqueue: This operation adds an element to the rear of the queue.
  • Dequeue: This operation removes and returns the element at the front of the queue.
  • IsEmpty: This operation checks if the queue is empty or not.
  • IsFull: This operation checks if the queue is full or not (in cases where there is a maximum capacity).
  • Peek/Front: This operation returns the element at the front of the queue without removing it.

The Real-World Analogies:

To better understand queues, let’s consider a few real-world analogies. Imagine you are waiting in line at a ticket counter or in a cafeteria.

The person who arrives first gets served first, while others have to wait for their turn. Similarly, when printing multiple documents from your computer, they are queued up and printed one by one.

In computer science and programming, queues are widely used for various applications. For example, they are used in scheduling algorithms, network management protocols, process management systems, and more. Queues provide an efficient way to manage resources and handle multiple tasks in a systematic manner.

Implementing Queues:

Queues can be implemented using arrays or linked lists. In the array-based implementation, a fixed-size array is used, while in the linked list implementation, nodes are dynamically allocated and connected to form a chain. Both implementations have their advantages and trade-offs, depending on the specific use case.

Time Complexity:

The time complexity of queue operations depends on the underlying implementation. In general, enqueue and dequeue operations have a time complexity of O(1) (constant time) when implemented efficiently. However, certain scenarios may require additional checks or resizing of data structures, which can result in higher time complexities.


In conclusion, queues are an essential data structure that follows the FIFO principle. They find applications in various domains of computer science and are used to manage resources efficiently. Understanding queues and their implementation is crucial for writing efficient algorithms and solving real-world problems.

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