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os-tutorial

从头创造一个操作系统！

这个教程完全是从@cfenollosa fork来的，这个教程将复杂的系统编写任务分解为很多简单步骤，在每一个小步骤中穿插着需要读者自学的简单知识点，几乎每一节课都有一点点积累，然后突然就在其中某个时刻完成了一个阶段性的目标，这是让人惊叹的教育手段，至少我本人佩服至极，所以在我第二次学习这个教程的过程中，顺便将教程做了粗糙的翻译，修正了个别bug，以作为@cfenollosa仓库的中文概览，如果能帮后来者节省一些时间，我将深感欣慰！

@cfenollosa的教程其实也是大量参考了别的英文的教程，os-dev是前面十几节课的参考书籍，可惜这本书没有写完
，但即使只是一本没有写完的书籍也绝对是神作，从BIOS到屏幕打印的接口，总是从初学者的角度娓娓道来，至少是本人见过最好的操作系统入门书籍。各位刚开始时，一定要细细的读os-dev这本书，然后尝试跟着本仓库的节奏写程序，出现任何问题，请对照仓库中现成的程序修改。

以下是@cfenollosa原文：

How to create an OS from scratch!

I have always wanted to learn how to make an OS from scratch. In college I was taught how to implement advanced features (pagination, semaphores, memory management, etc) but:

• I never got to start from my own boot sector
• College is hard so I don't remember most of it.
• I'm fed up with people who think that reading an already existing kernel, even if small, is a good idea to learn operating systems.

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.
• There is little theory. Yes, this is a feature. Google is your theory lecturer. Once you pass college, excessive theory is worse than no theory because it makes things seem more difficult than they really are.
• 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 - DONE!
• Enter 32-bit mode - DONE
• Jump from Assembly to C - DONE!
• Interrupt handling - DONE!
• Screen output and keyboard input - DONE!
• A tiny, basic libc which grows to suit our needs - DONE!
• 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

Contributing

This is a personal learning project, and even though it hasn't been updated for a long time, I still have hopes to get into it at some point.

I'm thankful to all those who have pointed out bugs and submitted pull requests. I will need some time to review everything and I cannot guarantee that at this moment.

Please feel free to fork this repo. If many of you are interested in continuing the project, let me know and I'll link the "main fork" from here.