Introduction to Stacks

Overview

• Starting a new chapter on stacks.
• Presentation outline:
  • Definition of stack
  • Real-life examples of stacks
  • Stack as an Abstract Data Type (ADT)
  • Stack operations (primary and secondary)

Definition of Stack

• A stack is a linear data structure.
• Insertions and deletions are allowed only at one end called the "top" of the stack.
• Comparison with arrays and linked lists:
  • In arrays and linked lists, insertions and deletions can be done anywhere.
  • In stacks, operations are restricted to the top.

Real-life Examples of Stacks

• Stack of Books:
  • Books can only be placed or removed from the top.
• Stack of Coins:
  • Coins are also accessed from the top.
• Visualize the stack as a glass jar:
  • Objects are placed in a closed jar, accessible only from the top.

Stack as Abstract Data Type (ADT)

• Focus on operations from the user's perspective.
• Users are not concerned with implementation details.
• Key point: Understanding types of operations that can be performed on the stack.

Stack Operations

Primary Operations

1. Push Operation:
   • Inserts data onto the stack.
   • Example: Adding an item to the top of the stack.
2. Pop Operation:
   • Deletes the last inserted element from the stack.
   • Example: Removing the top item from the stack.

Secondary Operations

1. Top Operation:
   • Returns the last inserted element without removing it.
2. Size Operation:
   • Returns the number of elements in the stack.
3. isEmpty Function:
   • Returns true if the stack is empty; otherwise, false.
4. isFull Function:
   • Returns true if the stack is full; otherwise, false.

Example Commands

1. Push one: Insert element "1" into the stack.
2. Push two: Insert element "2" into the stack.
3. Push three: Insert element "3" into the stack.
4. Pop: Remove the topmost element from the stack.
5. isFull: Check if the stack is full.

Conclusion

• Successfully covered the introduction to stacks.
• Next presentation will continue with further details.