Why Queue Is an Abstract Data Type?


Larry Thompson

Why Queue Is an Abstract Data Type?


A queue is an abstract data type (ADT) that follows the First-In-First-Out (FIFO) principle. It is a linear data structure that stores elements in a specific order.

In this article, we will explore the reasons why a queue is considered an abstract data type.

Definition of Abstract Data Type (ADT):

An abstract data type is a high-level description of how a particular data structure should behave, without specifying its implementation details. It defines the operations that can be performed on the data structure and the behavior of those operations.

The ADT encapsulates the essential characteristics of the data structure, allowing for different implementations while maintaining consistent functionality.

The FIFO Principle:

In a queue, elements are inserted from one end called the “rear” and removed from the other end called the “front.” This follows the FIFO principle, where the element that has been in the queue for the longest time gets removed first.

Imagine standing in a line or waiting in a queue; this is exactly how a queue behaves.

Operations on Queue:

  • Enqueue: Adding an element to the rear of the queue.
  • Dequeue: Removing an element from the front of the queue.
  • Peek/Top: Retrieving the element at the front of the queue without removing it.
  • isEmpty: Checking if the queue is empty or not.

Applying the ADT Concept:

The concept of abstract data types allows us to define the behavior and functionality of a queue without specifying how it should be implemented. This enables us to use the queue ADT in various programming languages and applications, depending on our specific needs.

Implementations of Queue:

There are multiple ways to implement a queue, such as using arrays or linked lists. The choice of implementation depends on factors like efficiency requirements, memory constraints, and the nature of the problem being solved.

However, regardless of the implementation details, the essential operations defined by the ADT remain consistent.

Real-World Examples:

Queues find applications in various real-world scenarios. Some examples include:

  • Printing documents: When multiple users send print requests simultaneously, a print queue manages the order in which the documents are printed.
  • Operating systems: The operating system uses queues for managing processes waiting to access shared resources like CPU or memory.
  • Call centers: Incoming customer calls are often placed in a queue until an agent becomes available.
  • Web servers: Incoming requests from clients are handled sequentially by placing them in a request queue.


In summary, a queue is an abstract data type that follows the FIFO principle. It allows for efficient management and ordering of elements.

By understanding queues as an abstract data type, we can implement them using different underlying data structures while maintaining consistent functionality across different programming languages and applications.

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