What Is a Queue Data Structure?


Larry Thompson

A queue data structure is a fundamental concept in computer science and programming. It is an abstract data type that represents a collection of elements in a specific order.

In a queue, the elements are stored and accessed based on the principle of “First-In-First-Out” (FIFO). This means that the element that is added first to the queue will be the first one to be removed.

Understanding the Queue Data Structure

In simple terms, imagine a real-life queue, like people waiting in line at a ticket counter. The person who arrives first gets served first, and new people joining the line are added at the end. Similarly, in programming, a queue follows this same principle.

Key Characteristics of a Queue

1. FIFO Order: As mentioned earlier, queues follow the FIFO order. The element that enters first will leave first. 2. Enqueue: The process of adding an element to the end of the queue is known as enqueue. 3.

Dequeue: The process of removing an element from the front of the queue is called dequeue. 4. Front: The front refers to the position where elements get dequeued from. 5. Rear (or Back): The rear (or back) refers to the position where new elements get enqueued.

Queue Operations

Queues support various operations, including:

1. Enqueue Operation:
To enqueue an element into a queue, follow these steps:

  1. Create space for a new element at the rear.
  2. Add the new element at that position.

2. Dequeue Operation:
To dequeue an element from a queue:

  1. Remove the element from the front position.
  2. Update the position of the front.

3. Peek Operation:
The peek operation allows you to access the front element of the queue without removing it.

Real Life Examples

Queues are utilized in various real-life scenarios, such as:

  • Print Queue: When multiple print jobs are sent to a printer, they are added to a queue and processed in the order they were received.
  • Call Center: Incoming customer calls are put into a queue and answered by agents based on their availability.
  • Traffic Management: Vehicles waiting at a traffic signal follow a queue-like structure, where the first vehicle to arrive gets the first chance to move forward.

Implementing Queues

Queues can be implemented using various programming languages. Some common approaches include using arrays or linked lists.

Queue Using Arrays

Implementing a queue using an array involves defining an array with a fixed size and two pointers: one for the front and one for the rear. As elements get enqueued or dequeued, these pointers get adjusted accordingly.

In this approach, enqueue and dequeue operations have time complexity O(1) since adding or removing elements from an array has constant time complexity.

Queue Using Linked Lists

Another way to implement queues is by using linked lists. In this approach, each element in the queue is represented by a node that contains both data and a pointer to the next node.

When implementing queues with linked lists, enqueue operations have time complexity O(1), but dequeue operations require updating only one pointer instead of shifting all elements, resulting in a time complexity of O(1) as well.


In conclusion, the queue data structure is an essential concept in computer science. With its FIFO order and efficient enqueue and dequeue operations, queues find applications in various real-life scenarios. Whether you’re managing print jobs, processing customer calls, or handling traffic flow, understanding and implementing queues will be valuable skills for any programmer.

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