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Data Structure Algorithm: Introduction to Queue

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In this article, learn the fundamentals of queues with our comprehensive introduction. Understand queues’ concepts, operations, and applications in computer science and beyond. Explore efficient implementations and gain insights into solving real-world problems using queues.

Table of Contents


Queue is the collection of Data elements inserted one by one. When the data element is inserted into it, it is called Enqueue; when deleted, it is called Dequeue. The data element at index 0 is the REAR (also Tail), and the existing element removed is the FRONT (also Head). 

It follows the procedure First In First Out (FIFO) and Last In Last Out (LIFO), meaning the element inserted first in the Queue will be the first to be removed, and the element inserted into the last will be the last to be removed.

E.g., If you go to the movie ticket counter to purchase movie tickets and you’re in the Queue first, you’re going to be the first one to get the tickets. Right? The same is the case for the Queue in the data structure.

In other words, 

A queue is a linear data structure in computer science that follows the First-In-First-Out (FIFO) principle. It is similar to a real-life queue or line, where the first person to join is the first to be served.

In a queue, elements are added to one end, called the rear or Tail, and removed from the other end, called the front or Head. This arrangement ensures that the element in the Queue for the longest time gets removed first, maintaining the order in which elements were added.

Source: AU

Some operations on Queue

Enqueue() − to add an object (store) to the Queue. 

Dequeue() − delete an object from the Queue (access).

Source: AU

Basic Features of Queue

  1. The Queue is often an ordered list of elements of related data types, like a stack.
  2. A FIFO(First In First Out) system is a queue.
  3. Once a new element is inserted in the Queue, it is important to remove all the elements inserted in the Queue before the new element is inserted, to delete the new element.

  4. The peek() function is often used to return, without dequeuing, the value of the first element.

Queue Applications

Queue, as the name indicates, is used if we need to treat any group of objects in an order in which the first one comes in while the others wait for their turn and also get out first, as in the following scenarios: 

  1. Serving demands, such as a printer, CPU task scheduling, etc., on a single shared resource.
  2. Call Center telephone networks to use lines in real-life situations to keep people calling them in order until a service representative is ready.
  3. Interrupt management of real-time applications. The interrupts are treated in the same order, i.e., first come, first served, as they arrive.

Queue Data Structure Implementation

An Array, Stack, and Linked List can be easily used for Queue, but the most suitable is the Array for implementing the Queue. 

Initially, at index number 0, the data elements are called Head(Front) and Tail(Rear). As the new data elements are inserted into the  Queue, the Tail keeps moving forward and denotes where the new element will be inserted, but the Head always stays at the index number 0.

Source: AU

Algorithm for running Enqueue

  1. Check to see whether or not the Queue is complete.

  2. If the Queue is complete, the program will print an overflow error and exit.

  3. If the Queue is incomplete, raise it and add an element to it.

Algorithm for working with Dequeue 

  1. Please check whether or not the Queue is empty.
  2. If the Queue is empty, the program will print an underflow error and exit.
  3. print the head element and increase the head value if the Queue is not empty.

Advantages and disadvantages


  • FIFO – First In, First Out ensures that the first element added to the Queue will be the first one to be removed from the Queue. It is just like the first person to join the Queue will be the first to be served.

  • Real-world Modeling – Queues in the data structure are the same as in real-world queues or lines. In real life, people follow the queues in tasks like first come, first serve, government of fice form submission, customer-care representative, etc.

  • Breadth-First Search (BFS): Queues are an integral part of the BFS algorithm, widely used in graph traversal. BFS explores nodes in levels, making it suitable for finding the shortest paths and solving certain graph problems.


  • Limited Access: Unlike arrays or lists, queues do not provide direct access to elements in the middle. To access elements other than the front or rear, it is necessary to dequeue elements until the desired element is reached.

  • Fixed Size Limitations: Queues have a fixed size limit in some implementations. If the Queue becomes full, adding more elements may result in an overflow condition. To overcome this limitation, dynamic implementations or resizing strategies can be used.

  • Inefficient Search: Queues are not designed for efficient searching or random access. If there is a need to search for a specific element in the middle of the Queue, it would require iterating through the elements sequentially.


Queues provide a comprehensive understanding of this fundamental data structure in computer science. It covers queues’ concepts, operations, and practical applications, allowing readers to understand their significance in various scenarios.

Queues provide a solid foundation for understanding and utilizing this essential data structure. By gaining insights into queues’ concepts, operations, and applications, readers can enhance their problem-solving skills and effectively manage data in various scenarios.

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