Lesson 1.3: The Operating System

Duration: 45 minutes

Learning Objectives

After completing this lesson, you will be able to:

• Explain what an operating system is and why it's necessary
• Identify the main functions of an operating system
• Name the major operating systems and their characteristics
• Understand how the OS serves as a bridge between you and the hardware

Introduction

You've learned about hardware (the physical parts) and software (the instructions). But how do they communicate? How does clicking a button on your screen turn into electrical signals that make things happen? The answer is the operating system — the most important piece of software on your computer.

Main Content

What is an Operating System?

An operating system (OS) is software that manages your computer's hardware and provides a platform for running applications. It's the first program that starts when you turn on your computer and the last one running when you shut it down.

Think of the OS as the conductor of an orchestra. The musicians (hardware components) are talented, but without the conductor coordinating them, they'd play chaotically. The OS makes sure everyone plays in harmony.

The Sandwich Model

Your computer works in layers, like a sandwich:

┌─────────────────────────────────────┐
│              YOU (User)             │  ← You interact here
├─────────────────────────────────────┤
│          Applications               │  ← Chrome, VS Code, Spotify
│      (Word, Games, Browsers)        │
├─────────────────────────────────────┤
│        OPERATING SYSTEM             │  ← The translator/manager
│    (Windows, macOS, Linux)          │
├─────────────────────────────────────┤
│            Hardware                 │  ← CPU, RAM, Storage, etc.
│     (Physical Components)           │
└─────────────────────────────────────┘

Applications don't talk directly to hardware — they go through the OS. This makes everything more secure and stable.

What Does the OS Do?

The operating system handles many critical tasks:

1. Process Management

The OS runs multiple programs simultaneously. Right now, you might have a browser, music player, and text editor open. The OS gives each program a slice of CPU time, switching between them so fast it feels like they're all running at once.

Program A ──┐
Program B ──┼──→ [OS Scheduler] ──→ [CPU]
Program C ──┘

The OS decides who gets CPU time and when

2. Memory Management

The OS decides how to divide RAM among running programs. When you open a new app, the OS finds free memory for it. When you close it, the OS reclaims that memory.

┌─────────────────────────────────────┐
│                RAM                   │
├──────────┬──────────┬───────────────┤
│  Chrome  │  Spotify │    Free       │
│  500 MB  │  200 MB  │   1300 MB     │
└──────────┴──────────┴───────────────┘

The OS tracks and allocates memory

3. File System Management

The OS organizes all your files and folders (which we covered in the previous lesson). It handles reading, writing, copying, and deleting files.

4. Device Management

When you plug in a USB drive, connect headphones, or use a printer, the OS detects the device and figures out how to communicate with it using drivers (special software for each device type).

5. User Interface

The OS provides the windows, icons, menus, and buttons you see on screen. This is called the Graphical User Interface (GUI). It also provides the command line interface (CLI) — the text-based terminal we'll learn about in the next module.

6. Security

The OS protects your computer by:

• Requiring login credentials
• Controlling which programs can access what
• Protecting system files from modification
• Managing permissions for files and folders

Major Operating Systems

The OS Family Tree

                    [Operating Systems]
                           │
          ┌────────────────┼────────────────┐
          │                │                │
     [Windows]         [Unix-like]      [Others]
          │                │
          │       ┌────────┴────────┐
          │       │                 │
          │    [macOS]           [Linux]
          │       │                 │
     Windows 11   │        ┌────────┼────────┐
     Windows 10   │        │        │        │
                iOS    Ubuntu   Fedora   Debian
                       Android

Fun fact: macOS, Linux, iOS, and Android are all related — they're based on or inspired by Unix, an operating system created in the 1970s.

Why Developers Care About the OS

As a programmer, the OS matters because:

1. Development tools differ between operating systems
2. Terminal commands are slightly different (Windows vs Mac/Linux)
3. File paths use different formats (/ vs \)
4. Some software only runs on certain operating systems
5. You may need to test your code on multiple platforms

Most web development can be done on any OS, but macOS and Linux are often preferred because their terminals are similar to the servers where code is deployed.

The OS as a Gatekeeper

When an application wants to do something (save a file, play sound, use the internet), it must ask the OS for permission. The OS then talks to the hardware.

[Your App] → "Save this file"
     ↓
[Operating System] → "OK, I'll tell the storage drive"
     ↓
[Storage Drive] → Actually writes the data
     ↓
[Operating System] → "Done!"
     ↓
[Your App] → Shows "File saved" message

This system prevents apps from interfering with each other and protects your hardware from buggy software.

Practice Exercise

Task 1: Identify Your OS

Answer these questions about your current computer:

1. What operating system are you using?
2. What version is it? (Hint: look in "About This Mac" or "Settings > About")
3. What is the name of your file browser? (Finder, File Explorer, etc.)
4. What is your terminal/command line called? (Terminal, Command Prompt, PowerShell)

Task 2: Watch Your OS Work

Open your system's task manager or activity monitor:

• Windows: Press Ctrl + Shift + Esc
• macOS: Press Cmd + Space, type "Activity Monitor"
• Linux: Open "System Monitor" or run top in terminal

Look at:

1. How many processes are running right now?
2. What percentage of your CPU is being used?
3. How much RAM is in use vs. available?

Task 3: Reflection

Think about this: Your OS started automatically when you turned on your computer. What would happen if there was no OS? Could you still use your computer?

Key Takeaways

• The operating system is software that manages hardware and runs applications
• It acts as a translator between you and the computer's hardware
• Main OS functions: process management, memory management, file system, device management, user interface, and security
• Major desktop operating systems: Windows, macOS, Linux
• Applications don't talk directly to hardware — they go through the OS
• As a developer, you'll interact with the OS through the terminal (next module!)

Resources