This is a book which will teach you how to create your own OS in just 30 days,
assuming only a small bit of prior experience in programming and nothing else.
This book is inspired by a japanese book with a similar title:

                       「30日でできる！ OS自作入門」
         ("Make it in 30 days! Introduction to self-made OS")

This book assumes that you are using a Windows operating system. Linux users
should search alternatives for the software provided in this book themselves.
Well, I try using the tools that are portable to begin with, but with some
software it becomes impossible to find such tools. In the future I'll probably
have to write these cross-platform tools myself, but for the time being please
cope.

Contributing

  You can join the discord server to receive help if you have any trouble or
  questions. We generally try to be helpful to beginners so don't be afraid to
  ask if you don't understand something:

    https://discord.gg/TkxhtTGVAu

  If you encounter a factual error/mistranslation/bad explanation/typographic error
  you can either file an issue at:

    https://github.com/handmade-osdev/os-in-30-days/issues/new

  Or create a pull request. How to do this is described below.

  All contributions are welcome. In order to submit an error, fork this
  repository to your hard drive. Then navigate to book/ subdirectory and find
  an .md file corresponding to the chapter number. Note that filenames starting
  with "!" do not correspond to chaters of the book, but rather to other
  sections of the book. Edit the markdown file to fix the error, then you will
  have to rebuild the book.html file. When editing .md files make sure to
  enable some kind of wrapping in your text editor. Otherwise you may
  experience difficulty editing the contents of the book. Avoid putting manual
  line breaks.

  For this make sure you've got pandoc installed. If you haven't got pandoc
  installed on your machine follow this URL:

    https://pandoc.org/installing.html

  Now you can build the book into an HTML document. Open your shell and type
  the command described next. Depending on your shell the command will look
  a bit different.

  Windows (cmd.exe):
    build

  POSIX shell or Powershell:
    ./build

  Now book.html should be updated. You can open this file in your browser and
  verify that the changes are correct and that there are no errors. After that
  you may commit your changes and create a pull request.

  Please check the following section to better understand the organization of
  the project.

Notes:

  1/ I have tried organizing the project in a way that would work for multiple
  OS's but it requires some assumptions, mainly that your OS sorts the folders
  alphabetically. It is important that the sort order in book/ folder is
  alphabetical. To check run `ls` (linux) or `dir` (windows) command and check
  whether the order is correct. It should look something like that:

    !000!-start.md
    !001!-preface.md
    !002!-toc.md
    00.md
    01.md
    02.md
    ...
    31.md

  If it does not, after you build the project the resulting HTML will have
  content in the wrong order. Note that different programs have different
  opinions on what constitutes "alphabetical sorting". The exclamation mark
  is a character whose codepoint is less than any other character or digit and
  its positions within filenames makes it so that different sorting algorithm
  no matter what sorts them correctly. If this causes any further issue I
  believe I'll have to write a utility that will concatenate files in the
  correct order.

  2/ When dealing with footnotes note that the footnote number is common for
  every single file in the book/ directory. The structure here is the following.

    file whose name starts with ! don't contain footnotes.
    chapter 0 contains footnote numbers 0..9
    chapter 1 contains footnote numbers 10..19
    chapter 2 contains footnote numbers 20..29
    ...
    chapter 31 contains footnote numbers 310..319

  This means that every chapter is limited to 10 footnotes. This simplifies the
  insertion and removal of footnotes.

  3/ Make sure that every file starts and ends with one or two empty lines.
  This is to make sure that after concatenation different files occupy at least
  different paragraphs.