# 9.1: Stacks

- Page ID
- 34683

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# Stack Data Structure

Stack is a linear data structure which follows a particular order in which the operations are performed. The order may be LIFO(Last In First Out) or FILO(First In Last Out).

The following four basic operations can be performed in the stack:

**Push:**Adds an item in the stack. If the stack is full, then it is said to be an Overflow condition.**Pop:**Removes an item from the stack. The items are popped in the reversed order in which they are pushed. If the stack is empty, then it is said to be an Underflow condition.**Peek or Top:**Returns top element of stack.**isEmpty:**Returns true if stack is empty, else false.

There are many real-life examples of a stack. Consider an example of plates stacked in the cupboard. The plate which is at the top is the first one to be removed, i.e. the plate which has been placed at the bottom most position remains in the stack for the longest period of time. So, it can be simply seen to follow LIFO(Last In First Out) / FILO(First In Last Out) order.

Adapted from: "Stack Data Structure (Introduction and Program)" by Bhupendra Rathore is licensed under CC BY-SA 4.0