**What Is Meant by Stack in Data Structure?**

A stack is a fundamental data structure in computer science that follows the Last In First Out (LIFO) principle. It can be visualized as a stack of plates where the last plate placed on top is the first one to be removed.

## Basic Operations on a Stack

A stack supports three main operations:

**Push:**This operation adds an element to the top of the stack. The new element becomes the top of the stack, and all other elements shift down.**Pop:**This operation removes and returns the element from the top of the stack. The next element becomes the new top.**Peek (or Top):**This operation returns the element at the top of the stack without removing it.

## Implementing a Stack

A stack can be implemented using various programming languages. Here’s an example of implementing a stack using JavaScript:

<script>class Stack { constructor() { this.stack = []; } push(element) { this.stack.push(element); } pop() { if (this.isEmpty()) { return "Stack Underflow"; } return this.pop(); } peek() { if (this.isEmpty()) { return "Stack is empty"; } return this.stack[this.length - 1]; } isEmpty() { return this.length === 0; } } // Example usage const myStack = new Stack(); myStack.push(10); myStack.push(20); console.log(myStack.peek()); // Output: 20 console.pop()); // Output: 20</script>

## Applications of Stacks

Stacks are used in various real-world applications, including:

__Function Call Stack:__Stacks are used to manage function calls within a program, keeping track of the order in which functions are called and return from.__Undo/Redo Operations:__Stacks can be used to implement undo and redo functionality in applications.__Expression Evaluation:__Stacks are utilized to evaluate arithmetic expressions, converting them from infix notation to postfix or prefix notation.__Backtracking Algorithms:__Stacks play a crucial role in backtracking algorithms, such as depth-first search.

### In Conclusion

A stack is an essential data structure that follows the Last In First Out principle. It supports operations like push, pop, and peek.

Implementing a stack involves using the appropriate programming language syntax. Stacks have various real-world applications and are widely used in computer science and software development.