A **stack** is a linear data structure that follows the Last-In-First-Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed.

In other words, elements are added and removed from only one end of the stack, known as the __top__. The operation to add an element to the top of the stack is called __push__, while removing an element from the top is known as __pop__.

## Examples of Stack Data Structure:

There are several examples of data structures that can be implemented using a stack. Some popular examples include:

**Function Call Stack:**In programming languages like C++, Java, and Python, function calls are managed using a stack. When a function is called, its return address and local variables are pushed onto the stack. When the function finishes execution, it pops these values off the stack to resume execution from where it left off.**Undo/Redo Operations:**Many applications provide an undo/redo feature that allows users to revert or repeat their actions. These operations can be implemented using stacks.Each action performed by the user is pushed onto a stack, and when undo is requested, it pops the last action from the stack and reverses its effects.

**Balanced Parentheses:**Another classic example of a stack-based problem involves checking whether parentheses in an expression are balanced or not. A stack can be used to keep track of opening parentheses encountered so far. Whenever a closing parenthesis is encountered, it can be compared with the top element of the stack to determine if they form a pair.**Infix to Postfix Conversion:**Infix expressions are the ones we commonly use, such as 2 + 3 * 4. Converting these infix expressions to postfix notation (also known as Reverse Polish Notation) can be done using a stack. The algorithm involves scanning the infix expression from left to right and pushing operators onto the stack based on their precedence.

These are just a few examples of how stacks can be used to solve various problems efficiently. Understanding and implementing stack data structures is essential for any programmer or software developer.

### In Conclusion:

A **stack** is a fundamental data structure that follows the Last-In-First-Out (LIFO) principle. It is used in many real-life scenarios and computer programs, including function calls, undo/redo operations, checking balanced parentheses, and converting infix expressions to postfix notation. By mastering stack operations like push and pop, you can enhance your problem-solving skills and become a more efficient programmer.