What Is a Queue Explain the Operations on a Queue Data Structure?


Heather Bennett

A queue is a fundamental data structure in computer science that follows the First-In-First-Out (FIFO) principle. It can be visualized as a line of people waiting for their turn, where the person who arrived first gets served first. In programming, a queue allows us to store and retrieve elements in a specific order.

Operations on a Queue

There are several common operations performed on a queue:


The enqueue operation adds an element to the end of the queue. The newly added element becomes the last element in the queue.

To enqueue an element, we use the following steps:

  • Create a new node or allocate memory for it.
  • Set the value of the new node to the desired element.
  • If the queue is empty, set both front and rear pointers to point to this new node.
  • Otherwise, set the next pointer of the current rear node to point to the new node and update the rear pointer accordingly.


The dequeue operation removes and returns an element from the front of the queue. The second person in line becomes the new front of the queue.

To dequeue an element, we use these steps:

  • If the queue is empty, throw an error or return null (depending on your implementation).
  • Create a temporary variable to store the value of the front node.
  • If there is only one node in the queue, set both front and rear pointers to null.
  • Otherwise, set the front pointer to the next node in line and deallocate memory for the temporary variable.
  • Return the value of the removed element.


The front operation returns the value of the element at the front of the queue without removing it.

To access the front element, we simply return the value stored in the front node without modifying any pointers.


The isEmpty operation checks if the queue is empty or not. It returns a boolean value indicating whether there are any elements in the queue or not.

To check if a queue is empty, we can simply compare if both front and rear pointers are null. If they are, then there are no elements present in the queue.


The size operation returns an integer representing the number of elements currently stored in the queue. It can be obtained by traversing through all elements and counting them one by one or by using an additional variable that keeps track of insertions and deletions.

In Conclusion

A queue is a versatile data structure that finds applications in various domains like operating systems, network protocols, and data processing algorithms. Understanding how to perform enqueue, dequeue, access front elements, check if it’s empty, and determine its size will help you efficiently handle data using queues in your programs.

Now that you have learned about queues and their operations, you can confidently implement them in your future projects!

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