os-tutorial

How to create an OS from scratch!

Inspired by this document and the OSDev wiki, I'll try to make short step-by-step READMEs and code samples for anybody to follow. Honestly, this tutorial is basically the first document but split into smaller pieces and without the theory.

Updated: more sources: the little book about OS development, JamesM's kernel development tutorials

Features

• This course is a code tutorial aimed at people who are comfortable with low level computing. For example, programmers who have curiosity on how an OS works but don't have the time or willpower to start reading the Linux kernel top to bottom.
• The lessons are tiny and may take 5-15 minutes to complete. Trust me and trust yourself. You can do it!

How to use this tutorial

1. Start with the first folder and go down in order. They build on previous code, so if you jump right to folder 05 and don't know why there is a mov ah, 0x0e, it's because you missed lecture 02. Really, just go in order. You can always skip stuff you already know.

2. Open the README and read the first line, which details the concepts you should be familiar with before reading the code. Google concepts you are not familiar with. The second line states the goals for each lesson. Read them, because they explain why we do what we do. The "why" is as important as the "how".

3. Read the rest of the README. It is very concise.

4. (Optional) Try to write the code files by yourself after reading the README.

5. Look at the code examples. They are extremely well commented.

6. (Optional) Experiment with them and try to break things. The only way to make sure you understood something is trying to break it or replicate it with different commands.

TL;DR: First read the README on each folder, then the code files. If you're brave, try to code them yourself.

Strategy

We will want to do many things with our OS:

• Boot from scratch, without GRUB
• Enter 32-bit mode
• Jump from Assembly to C
• Interrupt handling
• Screen output and keyboard input
• A tiny, basic libc which grows to suit our needs
• Memory management
• Write a filesystem to store files
• Create a very simple shell
• User mode
• Maybe we will write a simple text editor
• Multiple processes and scheduling

Probably we will go through them in that order, however it's soon to tell.

If we feel brave enough:

• A BASIC interpreter, like in the 70s!
• A GUI
• Networking