Is Queue Data Structure FIFO?


Heather Bennett

In computer science, a queue is an abstract data type that follows the FIFO (First-In, First-Out) principle. This means that the element that is inserted first will be the first one to be removed. In other words, it operates like a real-life queue, where people stand in line and are served in the order they arrived.

The Queue Data Structure

In programming, a queue is implemented as a linear data structure. Elements are added to one end of the queue called the rear, and they are removed from the other end called the front. This ensures that elements are processed in the order they were added.

Operations on a Queue:

A queue typically supports two fundamental operations:

  • 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.

The enqueue operation is responsible for adding elements to the queue, while dequeue removes them. The order in which elements are dequeued follows FIFO discipline.

An Example Scenario:

To better understand how a queue works, let’s consider an example scenario of customers waiting in line at a grocery store checkout counter:

  • The initial state:
    • The front of the queue is empty because no one has arrived yet.
    • The rear of the queue is also empty.
  • A new customer arrives:
    • The customer joins the end of the queue by enqueuing.
  • Another customer arrives:
    • This customer joins the end of the queue as well.
  • The cashier starts serving customers:
    • The front customer is dequeued and served.
    • The next customer in line becomes the new front.
  • More customers join the queue:
    • New customers always enqueue at the rear.
    • Customers are dequeued from the front and served one by one.


A queue data structure follows a FIFO (First-In, First-Out) order. It is commonly used in various computer science applications like process scheduling, network packet handling, and more. Understanding queues and their behavior is essential for efficient programming and problem-solving.

Remember, when working with queues, always keep track of the front and rear ends to maintain proper order and ensure that elements are processed in a fair manner.

Now that you have a better understanding of queues and their FIFO behavior, you can utilize this knowledge to design efficient algorithms and solve a variety of problems!

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