Operating Systems Interview Questions

An operating system (OS) is system software that sits between computer hardware and the applications/users, managing hardware resources and providing a controlled, stable environment in which programs execute. Without an OS, every application would need its own drivers, memory-management code, and I/O routines, so the OS abstracts this complexity behind standardized APIs (system calls).

Its core responsibilities are usually grouped into: (1) Process management - creating, scheduling, and terminating processes/threads and switching the CPU between them; (2) Memory management - allocating RAM, implementing virtual memory, and protecting one process's memory from another; (3) File system management - organizing how data is stored, named, and retrieved on storage devices; (4) Device/I/O management - providing a uniform interface to disks, printers, network cards, etc., via drivers; (5) Security and access control - enforcing permissions and isolating processes from each other; and (6) Providing a user interface (CLI or GUI) and the system-call API applications use to request these services.

In short: the three things that separate an OS from ordinary software are resource allocation (deciding who gets CPU/RAM/I/O), isolation (keeping processes from corrupting each other), and abstraction (hiding hardware-specific details behind consistent interfaces). An interviewer usually wants you to name these responsibilities and briefly explain why each matters (e.g., without process isolation, one buggy program could crash the whole system).