During the holiday, I was bored on the express bus, so I clicked on the lecture on Nulltube [Operating System] and started learning about it. (ps: The Infraon OS lecture was included when I purchased the entire roadmap. ㅠ) My first impression after studying the operating system was, "My vision has widened so much." After turning on the computer, the OS program runs, the game program runs, it goes into memory (virtual memory structure), and it uses the Internet to communicate (this part is a network basics lecture). It was amazing how all these processes were roughly connected. Personally, when I had to do work that went beyond the "program internal (code editor) scope," I was really scared and broke out in a cold sweat, but now I feel a little "liberated." Thank you for making it fun and easy to get started on the operating system! [One-line summary] This is the lecture that led me, who knew nothing, to study the entire Computer Science!!