# Difference Between Stack and Queue

The primary difference between Stack and Queue Data Structures is that Stack follows LIFO while Queue follows FIFO data structure type. LIFO refers to Last In First Out. It means that when we put data in a Stack, it processes the last entry first. Conversely, FIFO refers to First In First Out. It means that when we put data in Queue, it processes the first entry first. Let us understand further the differences between them.

## What is a Stack Data Structure?

You can refer to Stack as a linear form of data structure. In this, a user can delete and insert elements from only one side of a list. It is known as the top. The stack data structure implements and follows the Last In, First Out (LIFO) principle. It implies that the element that is inserted last comes out first.

The process of inserting an element in the stack is known as the push operation. Here, the deletion of elements is known as the pop operation. A user can feasibly keep track of the last function/element of the list in a stack using a pointer (top).

## What Is a Queue Data Structure?

You can also refer to Queue as a linear form of data structure. In this, a user can insert elements from only one side of the list. It is known as the rear. Also, one can delete these elements from another side- known as the front. This type of data structure implements and follows the First In, First Out (FIFO) principle. It implies that the first element that inserts into a list will come out first.

The process of inserting an element into a queue is known as the enqueue operation. Here, the process of deleting an element is known as the dequeue operation. A user can always hold two pointers in a queue. The front pointer points to the first inserted element that is still in the list. The second pointer is the rear one that points to the last inserted element in the list.

## Difference Between Stack and Queue

 Parameter Stack Data Structure Queue Data Structure Basics It is a linear data structure. The objects are removed or inserted at the same end. It is also a linear data structure. The objects are removed and inserted from two different ends. Working Principle It follows the Last In, First Out (LIFO) principle. It means that the last inserted element gets deleted at first. It follows the First In, First Out (FIFO) principle. It means that the first added element gets removed first from the list. Pointers It has only one pointer- the top. This pointer indicates the address of the topmost element or the last inserted one of the stack. It uses two pointers (in a simple queue) for reading and writing data from both the ends- the front and the rear. The rear one indicates the address of the last inserted element, whereas the front pointer indicates the address of the first inserted element in a queue. Operations Stack uses push and pop as two of its operations. The pop operation functions to remove the element from the list, while the push operation functions to insert the element in a list. Queue uses enqueue and dequeue as two of its operations. The dequeue operation deletes the elements from the queue, and the enqueue operation inserts the elements in a queue. Structure Insertion and deletion of elements take place from one end only. It is called the top. It uses two ends- front and rear. Insertion uses the rear end, and deletion uses the front end. Full Condition Examination When top== max-1, it means that the stack is full. When rear==max-1, it means that the queue is full. Empty Condition Examination When top==-1, it indicates that the stack is empty. When front = rear+1 or front== -1, it indicates that the queue is empty. Variants A Stack data structure does not have any types. A Queue data structure has three types- circular queue, priority queue, and double-ended queue. Visualization You can visualize the Stack as a vertical collection. You can visualize a Queue as a horizontal collection. Implementation The implementation is simpler in a Stack. The implementation is comparatively more complex in a Queue than a stack.

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