NonOS

NonOS is a term used in computing to describe software that runs without a traditional operating system. In practice, nonOS software executes directly on hardware or within a minimal runtime, without the general-purpose services provided by an OS, such as process scheduling, virtual memory, or file systems.

The term is not standardized, but it is commonly applied to bare-metal programs on microcontrollers, firmware for devices, bootloaders, and certain embedded systems. Some discussions also include unikernel approaches that present a specialized, single-address-space environment rather than a full OS.

NonOS software typically runs with limited or no isolation between tasks, direct hardware access, and small or custom runtimes. It may use a simple event loop or a real-time scheduler implemented by the application. Memory management is often explicit and static, reflecting the constraints of minimal systems.

Benefits and challenges include lower overhead, deterministic execution, and tighter control over hardware resources. Drawbacks encompass portability issues, debugging difficulty, lack of standard services, and greater responsibility for safety, security, and hardware compatibility.

Examples and related concepts: Common domains include firmware for embedded devices, bootloaders, and bare-metal applications on microcontrollers. Related topics include bare-metal programming, firmware, embedded systems, real-time operating systems, and unikernels. While nonOS emphasizes the absence of a conventional OS, many projects mitigate some limitations with lightweight runtimes or specialized abstractions.