Real-time operating system

A real-time operating system schedules computation so tasks meet specified timing constraints. Its central guarantee is predictable response, not necessarily the shortest average execution time.

Real-time scheduling: The allocation of processor time to tasks with timing constraints. Scheduling policies decide which task runs next and whether deadlines remain achievable.
Deadline (computing): The latest time by which a computing task or result must be completed. A real-time task is judged by whether it completes before its deadline.
Embedded system: A computer system built into a larger device to perform a dedicated function. Many real-time operating systems run inside embedded devices with limited resources.
General-purpose operating system: An operating system designed to support a broad range of applications and users. General-purpose systems often optimize average responsiveness rather than strict deadline guarantees.
VxWorks: A commercial real-time operating system developed by Wind River. VxWorks is used in embedded systems that require predictable scheduling and response.
Preemption: The suspension of a running task so another task can use the processor. Preemption lets urgent tasks interrupt less urgent work.
Deterministic system: A system whose behavior is sufficiently predictable to produce consistent results under specified conditions. Predictability makes timing guarantees possible to state and analyze.
Automotive embedded system: An embedded computer system that monitors or controls functions in a vehicle. Vehicle control tasks must respond within bounded times to sensors and driver inputs.
Hard real-time system: A real-time system in which missing a specified deadline is considered system failure. This is the strictest deadline model commonly supported by real-time operating systems.
QNX: A commercial operating system with a microkernel design, widely used in embedded systems. QNX provides a deployed example of a real-time operating system built around message passing.

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