# Difference between Stack and Queue Data Structure

By Anjnee Bhatnagar|Updated : May 5th, 2022

Difference between Stack and Queue: Stack and Queue are linear data structures used to store and organize data. There are difference between Stack and Queue, the most basic one being the approach they follow to store data. The major difference between Stack and Queue is that stack follows LIFO whereas queue follows FIFO.

To discuss the difference between stack and queue, we will first see what the meaning of data structure is, types of data structure, stack data structure, and queue data structure. Let us understand the difference between Stack and Queue starting with the meaning of data structure.

## What is a Data Structure?

Data may be organized in many different ways. The logical or mathematical organization of data is called the data structure. Data structures are used by programming languages to store, manipulate, access, and organize data. Algorithms are implemented using these data structures.

The data structures are broadly classified into two categories based on their operations. The two categories are a Linear data structure and a Non-linear data structure. In the linear data structure, we have linear arrangements of data while in the non-linear data structure the data is stored in the form of trees, tables, etc. Despite the difference between Stack and Queue both stack and queue belong to the linear data structures.

## What is a Stack Data Structure?

A stack is an abstract data type (ADT). A real-world stack allows operation at one end only. At any given point in time, we can only access the top element of a stack. This feature makes it a LIFO data structure. LIFO stands for Last In First Out. The operational difference between stack and queue involves LIFO and FIFO (First In First Out), we will learn about FIFO in the queue data structure. The basic operations of the stack data structure are:

1. push(): Insert an element into the stack.
2. pop(): Removing an element from the stack.
3. peek(): Get the top element of the stack without removing it.
4. isFull() : Checks if the stack is full.
5. isEmpty(): Checks if the stack is empty.

## What is a Queue Data Structure?

A queue is an abstract data structure similar to a stack. Unlike stacks, a queue is open at both its ends. One end is always used to insert data and the other end is used to remove data from the queue. Queue follows the FIFO methodology. The end at which insertions take place is called the rear end of the queue and the end at which deletion takes place is called the front of the queue. The basic operations of queue data structures are:

• enqueue() : To insert an item into the queue.
• dequeue() : To remove an element from the queue.
• peek(): To get the element from the front of the queue without removing it.
• isFull() : Checks if the queue is full.
• isEmpty() : Checks if the queue is empty.

## Difference Between Stack and Queue

Having discussed the data structures, their types, stack data structure, and queue data structure, now we will see the difference between Stack and Queue. Though both stack and queue belong to the linear data structures there exist differences based on operations and features each one offers to the programmer or user. The differences between stack and queue are as follows:

 Stack Queue Elements are inserted or deleted from the same end called the top of the stack. Elements are inserted and deleted respectively from the rear and front end of the queue. It follows LIFO It follows FIFO It uses push and pop operations to insert and delete data respectively. It uses enqueue and dequeue operations to insert and delete data respectively. A stack has no further division. A queue is divided into the circular queue, priority queue, and double-ended queue. Implementation is simple. Implementation is complex. Used in expression evaluation, undo, and redo operations. Used in assigning processes, ready queue, wait for queue etc.

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## FAQs

• A stack data structure follows the LIFO methodology while a queue data structure follows the FIFO methodology. LIFO stands for Last in first out. FIFO stands for First in first out. A stack with LIFO is a simple to build data structure using an array.

• A stack data structure follows LIFO. All operations are performed on the same end of the stack. The stack operations are: pop(), push(), peek(), isFull(), and isEmpty().

• The differences between stack and queue reveal each one has its operational features. The stack data structure is simple to implement and has applications in expression evaluation, balancing parentheses, performing undo, redo operations, etc.

• A data structure is used to organize data mathematically or logically. Data structures are broad of two types linear and non-linear. The linear data structures involve arrays, linked lists, stacks, and queues. Non-linear include graphs, trees, sets etc.

• A queue data structure involves various operations to be performed by the user like enqueue, dequeue, peek, etc. The major operations to insert and delete elements from queue data structure are called enqueue and dequeue respectively.