Chapter 4: Stacks, Queues, & Deques

"State management is the root of all bugs."

🏛️ The Academic View

LIFO (Last-In, First-Out) and FIFO (First-In, First-Out) are simple abstract data types.

🏗️ The Engineering Reality

These structures are the backbone of user interaction (Undo/Redo) and system stability (Job Queues).

Key Topics: * The Browser Engine: Implementing a robust Undo/Redo system using dual stacks. * Thread Safety: Why list is not a thread-safe Queue, and why you must use collections.deque.