Should know something about OS

As a graduate student majoring in computer science, I shoud have learned something more deeply about operating system. No matter Unix or Windows, I shoud be familiar with them and the mechanisms of them. But before I entered gucas, I had not even used linux. When it came to windows, I knew nothing of its mechanism. As a programmer , I did not familiar with its API. From the four years' study in college, I have understood little on operating system expect the knowledge from our textbook. So I must relearn the operating system course and learn the mechanisms of linux and windows--at least get familiar with the APIs of them.