# What Are Stack and Queue in Data Structure?

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Larry Thompson

What Are Stack and Queue in Data Structure?

When it comes to organizing and manipulating data, two essential data structures come into play – the stack and the queue. These structures have their own unique characteristics and are used in various real-life scenarios. In this article, we will explore the concepts of stack and queue, their differences, and their applications.

## The Stack Data Structure:

A stack is a linear data structure that follows the Last-In-First-Out (LIFO) principle. Imagine a stack of plates in a restaurant; the last plate added is always the first one to be removed. Similarly, in programming, a stack allows adding or removing elements only from one end, known as the top of the stack.

Key Characteristics of a Stack:

• A new element is always added at the top
• The topmost element can be accessed or removed
• Elements below the top cannot be accessed unless removing all elements above them

Applications of Stacks:

The stack data structure finds applications in various scenarios that include but are not limited to:

• Undo/Redo functionality in text editors or graphic software
• Function call management in programming languages
• Expression evaluation and syntax parsing
• Backtracking algorithms like Depth-First Search (DFS)

## The Queue Data Structure:

A queue is another linear data structure that follows the First-In-First-Out (FIFO) principle. Think of a queue at a ticket counter; the person who arrived first gets served first. In programming, a queue allows adding elements at one end, called the rear, and removing elements from the other end, known as the front.

Key Characteristics of a Queue:

• New elements are always added at the rear
• Elements are removed from the front
• The first element added is always the first one to be removed

Applications of Queues:

The queue data structure finds applications in various scenarios including but not limited to:

• Serving requests in operating systems or computer networks
• Task scheduling in operating systems
• Breadth-First Search (BFS) algorithm for graph traversal
• Synchronization between producer-consumer threads in concurrent programming

## Differences Between Stack and Queue:

1. Order of Elements:

In a stack, the order of elements is determined by the Last-In-First-Out (LIFO) principle. On the other hand, a queue follows the First-In-First-Out (FIFO) principle.

2. Accessing Elements:

In a stack, only the topmost element can be accessed or removed. In contrast, a queue allows accessing or removing elements from both ends – front and rear.