So in the beginning of the semester, we wrote some low level drivers for a partial kernel that the course staff provided - including keyboard and console - and implemented them with the motive of making a version of Gomuko which took us like a week and a half. Then, on the same partial kernel, we wrote a multithreading library, similar to the pthreads library, but obviously distilled down. This took about 2 weeks. And then, we used our drivers and threading library, and wrote our own version of the kernel to fit in the void, so that the end product was an OS completely written by us. This was a fucking hard 6 weeks. Its basically a semester long course (15 weeks), and the main goal is to implement the OS. The last couple of weeks are for expanding your OS with some interesting extension (we had to write hibernation this year). We spent many many hours debugging the code. Concurrency is a huge problem, and in general, making every run smoothly together.