STACK  INTRODUCTION:

                                       Stack is a linear data structure which allows any kind of operations on only top of the stack.Stack fallows particular order only i.e LIFO(Last In First Out) or FILO(First In Last Out).

• Mainly the following three basic operations are 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: Get the item from stack with out pop.

How to understand a stack practically?

• There are many real life examples of stack. Consider the simple example of plates stacked over one another in canteen. 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/FILO order.

Implementation:
                          There are two ways to implement a stack:

1. Using array
2. Using linked list