Glossary · Automation software engineering and architecture
Real-time operating system (RTOS)
Also known as: RTOS, Real-time OS
German: Echtzeitbetriebssystem (RTOS)
In embedded computing, a real-time operating system (RTOS) is an operating system designed to execute tasks within bounded, predictable time, typically offering priority-based preemptive scheduling, fast interrupt handling and deterministic synchronization.
- Software engineering
In one sentence
A real-time operating system (RTOS) executes tasks within bounded, predictable time using priority-based preemptive scheduling.
Example
The servo drive firmware runs on an RTOS that guarantees the current control task starts within a few microseconds of its timer interrupt.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: An RTOS provides the building blocks (tasks, priorities, mutexes with Priority inheritance, timers) for meeting deadlines. Whether deadlines are actually met depends on the application design and its timing analysis.
- Functional safety: For safety-related software, some RTOS products are offered with certification evidence for IEC 61508. Using such an RTOS does not make the application safe; it supports the argument.
- Documentation: State the RTOS and version in the software configuration records and the third-party component list. Timing figures in technical data (cycle times, jitter) should be traceable to measurements on the target.
RTOS vs. general-purpose operating system
A general-purpose OS optimizes average throughput and fairness. An RTOS optimizes predictability: bounded latency and Jitter, even if average performance is lower.