↩ 🔵 🔵 🔵 ❪✺❫ Operating System Concepts ○ ❪✺₁₀❫ Computer Class Portals ○ Operating System ○꠹ ❪✺₁❫ Unix Classes ○ File System ○꠹ Kernel ○꠹ Shell ○꠹ System Call ○꠹