How to create an operating system.
Book and source code
https://www.gitbook.com/book/samypesse/how-to-create-an-operating-system
https://github.com/SamyPesse/How-to-Make-a-Computer-Operating-System
A hobby operating system, in Rust
https://github.com/intermezzOS/kernel (code)
http://intermezzos.github.io/book/
Operating System From Scratch : learn OS by practice
https://github.com/yyu/osfs01
Simple operating system in C++, written from scratch
https://github.com/wichtounet/thor-os
Original link
SPM' Notes 