MikeOS

From LXF Wiki

MikeOS is a computer operating system created by Linux Format's very own Mike Saunders. It is released under a free software license and is available from BerliOS at:

http://mikeos.berlios.de

It is intended to help teach OS design, and is written in x86 assembler. According to Mike, it is a "mini OS for first-time OS developers and those learning x86 assembly, with complete documentation from start to finish."

So it also comes with a comprehensive handbook covering the basics of x86 assembly language and the PC boot process, as well as OS design and how MikeOS works.