What Is Circular Queue Data Structure?


Larry Thompson

A circular queue is a data structure that follows the FIFO (First-In-First-Out) principle. It is similar to a regular queue, but with a slight variation. In a circular queue, the last element is connected to the first element, forming a circle.

Why Use Circular Queue

Circular queues are used in scenarios where we need to access elements in a cyclical manner. Some common use cases include:

  • Buffering of data in networking systems
  • Implementing CPU scheduling algorithms
  • Maintaining history in GPS navigation systems

How Does Circular Queue Work

A circular queue can be implemented using an array or linked list. Here, let’s explore the array-based implementation:

  • Front: The index of the first element in the circular queue.
  • Rear: The index of the last element in the circular queue.
  • Capacity: The maximum number of elements that can be stored in the circular queue.
  • Size: The current number of elements present in the circular queue.

To perform operations on a circular queue, we need to keep track of these four parameters. Let’s understand how each operation works:


The enqueue operation adds an element to the rear end of the circular queue. If there is space available, it inserts the element and updates the rear index accordingly. However, if there is no space left, it indicates an overflow condition.


The dequeue operation removes the element from the front end of the circular queue. If there are elements present, it removes the element and updates the front index accordingly. If there are no elements, it indicates an underflow condition.


The IsFull operation checks if the circular queue is full. It returns true if the number of elements is equal to the capacity; otherwise, it returns false.


The IsEmpty operation checks if the circular queue is empty. It returns true if there are no elements present; otherwise, it returns false.

Advantages of Circular Queue

  • Efficient memory utilization as it avoids wasted space.
  • Simplified implementation compared to other data structures like linked lists.
  • Ability to access elements in a cyclical manner.
  • Fast insertion and deletion operations with a constant time complexity of O(1).

Limitations of Circular Queue

  • A fixed size needs to be defined during initialization.
  • If not implemented carefully, it can lead to logical errors and bugs.
  • The maximum capacity cannot be changed dynamically.

Closing Thoughts

A circular queue is a powerful data structure that offers efficient memory utilization and simplified implementation. Its ability to access elements in a cyclical manner makes it suitable for various applications. However, it is essential to understand its limitations and implement it correctly to avoid any potential issues.

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