Stack Basics

Introduction to Stacks

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. It allows operations at one end only, typically referred to as the 'top' of the stack. Stacks are used in various applications such as expression evaluation, backtracking, and function call management.

Components of Stacks

The primary components of a stack include:

  • Elements: The individual values stored in the stack.
  • Top: The position of the last inserted element, which is the only accessible element for stack operations.
  • Size: The total number of elements that the stack can hold.

Operations on Stacks


Push involves adding a new element to the top of the stack.

  • Implementation: Increment the top index and place the new element at this position.


Pop involves removing the top element from the stack.

  • Implementation: Remove the element at the top index and decrement the top index.


Peek involves accessing the top element without removing it from the stack.

  • Implementation: Return the element at the top index without modifying the stack.


IsEmpty checks whether the stack is empty.

  • Implementation: Return true if the top index is -1, indicating that there are no elements in the stack.


IsFull checks whether the stack is full.

  • Implementation: Return true if the top index is equal to the maximum size of the stack minus one.

Applications of Stacks

  • Expression Evaluation: Used to evaluate arithmetic expressions in infix, prefix, and postfix notations.
  • Backtracking: Used in algorithms such as maze solvers and recursive problem-solving techniques.
  • Function Call Management: Used by the system to manage function calls, local variables, and return addresses.
  • Undo Mechanism: Used in text editors and software applications to implement undo functionality.


Stacks are a fundamental data structure that provides efficient management of elements using the LIFO principle. Understanding their components, operations, and applications is crucial for implementing various algorithms and solving complex problems.