Os

An operating system (OS) is system software that manages computer hardware and provides services for application software. It acts as an intermediary between users, applications, and hardware, coordinating resources such as CPU time, memory, storage, and I/O devices.

Core tasks include process management (scheduling, creation, termination), memory management (allocation, paging, caching), file systems (naming, reading, writing, permissions), device drivers, networking, security, and input/output orchestration. The OS provides a user interface, either command-line, graphical, or both.

Architecture and design vary across systems. Most OS have a kernel that runs in protected mode and mediates access to hardware. Kernels differ in design: monolithic kernels combine services in a single address space; microkernels keep core features small and delegate others to user-space servers; hybrid designs blend approaches. The OS also includes libraries, system services, and utilities in user space.

Types and examples span desktop, server, embedded, and real-time domains. General-purpose OS include Windows, macOS, Linux distributions, and BSD variants. Mobile and embedded systems include Android and iOS; embedded real-time OS target deterministic timing, used in automotive, aerospace, and industrial control. Real-time OS emphasize predictable response times and often prioritize determinism over throughput.

History and open-source development have shaped modern OS. They evolved from batch processing to time-sharing, multitasking, and virtualization, with Unix and its descendants influencing many systems. Linux and BSD are prominent open-source flavors used in servers, desktops, and devices.

In programming, the term os may refer to the operating-system interfaces provided by languages. For example, Python’s os module exposes a portable API for file I/O, environment variables, and process management.