Operating Systems Foundations

Lesson Promise

By the end of this lesson, you will understand what an operating system is, what a process is, the five process states, and how processes differ from threads.

Narration Draft

Part 1 — What Is an OS? (3:00) An operating system is a resource manager and abstraction layer. Kernel vs user mode. The four roles: resource manager, abstraction layer, extended machine, file system.

Part 2 — What Is a Process? (4:00) A process is an executing program with its own memory and identity. Process Control Block (PID, state, registers, page tables). The five states.

Part 3 — Process Lifecycle Trace (4:00) Walk through fork() → ready queue → scheduled → running → I/O wait → ready → running → exit. Show context switches.

Part 4 — Process vs Thread (4:00) Memory isolation, creation cost, communication, failure boundaries. When to use each.

Visual Sequence

1. OS layering: application → kernel → hardware
2. Process Control Block fields (PID, state, registers, page tables)
3. State transition diagram: New → Ready → Running → Waiting → Terminated
4. Context switch: save state A, restore state B
5. Process vs thread: separate address spaces vs shared memory

Companion Material

• Article: What Is an Operating System?
• Article: What Is a Process?
• Diagram: Process vs Thread
• Trace: Process Lifecycle
• Practice: Identify Process States
• Interview: Process vs Thread