Summary

An operating_system is the core software that manages hardware and runs programs. Remember these roles: process_management, memory_management, file_system, io_management, and cpu_scheduling. The kernel runs in kernel_mode, offers system_calls, and handles interrupts. User programs run in user_mode. virtual_memory isolates processes and expands usable memory. The OS provides concurrency and basic security through permissions and isolation. Common examples include Linux, Windows, and macOS.