Stack is a linear data structure that follows the LIFO (Last In First Out) principle. Elements are inserted and removed from the top of the stack. Stack can be implemented using arrays or linked lists. Common stack operations are push, which adds an element to the top, and pop, which removes an element from the top.

1. Stack Y S N L Srihari

8. Diagrammatical representation of Stack 20 10 30 50 Inserting position Removing position

9. Push and Pop operations Push an element ’45’ into stack Pop an element ’45’ from stack 20 10 30 50 45 20 10 30 50 45 20 10 30 50 45

12. Example: Data Address link 10 * 20 * 30 * 40 NULL Top

13. Push operation: 10 * 20 * 30 * 40 NULL Top New node 45 Null Before Push: 45 Null 10 * 20 * 30 * 40 * Top Step 1: Step 2: 45 Null 10 * 20 * 30 * 40 * Top

14. Push operation: Before Pop: 45 Null 10 * 20 * 30 * 40 Null Top Step 2: Step 1: 45 Null 10 * 20 * 30 * 40 * Top Temp