**What Is Stack in Data Structure and Its Application?**

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.

In programming, a stack is an abstract data type with two main operations: *push* and *pop*.

## Operations on a Stack:

1. **Push:** The push operation inserts an element onto the top of the stack.

This operation is also known as “pushing onto the stack” or “adding to the stack.”

2. **Pop:** The pop operation removes the topmost element from the stack.

This operation is also known as “popping from the stack” or “removing from the stack.” The element that is popped out is usually returned to further process it.

## The Stack Data Structure:

A stack can be implemented using various data structures, such as arrays and linked lists. Here, we will discuss the implementation using arrays.

To implement a stack using an array, we need to keep track of two things:

- The capacity of the stack (maximum number of elements it can hold)
- The index of the topmost element in the array (initially -1)

### Pseudocode for Push Operation:

```
function push(element):
if top == capacity - 1:
print "Stack Overflow: Cannot push element"
else:
top = top + 1
stack[top] = element
```

### Pseudocode for Pop Operation:

```
function pop():
if top == -1:
print "Stack Underflow: Cannot pop element"
else:
element = stack[top]
top = top - 1
return element
```

## Applications of Stacks:

Stacks have various applications in computer science and real-world scenarios. Some common applications include:

- Function call and recursion: Stacks are used to store variables, return addresses, and other function call-related information.
- Expression evaluation: Stacks are used to evaluate postfix expressions or convert infix expressions to postfix form.
- Undo operations: Stacks can be used to implement undo functionality in text editors or software applications.
- Backtracking algorithms: Stacks can be used in backtracking algorithms like Depth-First Search (DFS).
- Memory management: Stacks play a crucial role in managing memory allocation and deallocation.

In conclusion, a stack is a vital data structure with various practical applications. Its simple yet powerful nature makes it an essential concept for every programmer to understand.

By mastering stacks, you will be able to solve complex problems efficiently.