Learn the fundamental concepts of stacks, the LIFO (Last In, First Out) principle, and discover how this simple yet powerful data structure is used everywhere in computer science.

Learning Objectives

Stack Concept

Understand what a stack is and its properties

LIFO Principle

Master Last In, First Out operations

Real Applications

Discover how stacks are used in programming

What is a Stack?

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. Think of it like a stack of plates - you can only add or remove plates from the top.

Key Characteristics:

Linear data structure

LIFO (Last In, First Out) ordering

Access only from one end (top)

Dynamic size (can grow/shrink)

Stack Visualization

Element 3 (Top)

Element 2

Element 1 (Bottom)

↑ Push/Pop operations happen here

LIFO Principle in Action

LIFO means the last element added to the stack will be the first one to be removed. This is the fundamental principle that defines stack behavior.

Push Operation

Adding an element to the top of the stack

stack.push(element)

// Adds to top

Pop Operation

Removing the top element from the stack

element = stack.pop()

// Removes from top

Step-by-Step Example

push(1) → [1]

push(2) → [1,2]

push(3) → [1,2,3]

pop() → returns 3

[1,2]

pop() → returns 2

[1]

Real-World Stack Examples

Function Calls

Call stack manages function execution

main() calls

foo() calls

bar() // top

Browser History

Back button uses stack behavior

Current Page (top)

Earlier Page

Undo/Redo

Text editors use stacks for undo

Latest Change (top)

Previous Change

Earlier Change

Expression Evaluation

Parsing mathematical expressions

((3+4)*2)

Uses operator stack

Memory Management

Stack memory for local variables

Local variables

Function parameters

Return addresses

Syntax Parsing

Matching parentheses, brackets

{ "[" "(" ")" "]" }

Balanced checking

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