Pintos is a simple operating system framework for the 80x86 architecture. There are four projects. Project 1: Threads, Project 2: Multiprogramming, Project 3: Virtual Memory, Project 4: File Systems. Since it's educational materials, I was able to see the provided documents and implement missing parts in the source code.
Completed all projects by myself and understand the basic concepts of the operating systems. I could understand why such concepts were created and how computer scientists solved them.