A simple UNIX-like toy operating system for the x86 architecture. Still work in progress.
https://littleosbook.github.io/
http://www.jamesmolloy.co.uk/tutorial_html/
https://wiki.osdev.org/Main_Page
https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-3a-part-1-manual.html/