A real-time operating system (RTOS) is an operating system for real-time computing applications that processes data and events with defined time constraints. A RTOS is different from a time-sharing operating system, such as Unix. Let’s see how?
Unix OS manages the sharing of system resources with a scheduler, data buffers, or fixed task prioritization in multitasking environments. All operations must complete within the given time. Here priority within the tasks can be changed or can be fixed.
Real-time operating systems (RTOS) are event-driven and preemptive, meaning the OS can monitor the relevant priority of competing tasks, and make changes to the task priority.
Characteristics
Hard RTOS
A Hard RTOS is a type of real-time operating system in which missing a deadline is considered a system failure. The system must respond to events within strict timing constraints, and these constraints are non-negotiable.
Exa: VxWorks , QNX Neutrino
VxWorks RTOS has been widely used in critical applications for decades including Mars rovers, Boeing 787s and other industrial applications.
QNX Neutrino RTOS is also commonly used in applications requiring precise timing and robustness. It is widely used in various industries, including automotive, railway and healthcare.
Soft RTOS
A Soft RTOS is a type of real-time operating system where meeting deadlines is important, but not strictly mandatory. Missing an occasional deadline does not lead to system failure, but may result in reduced performance or quality of service (QoS).
Exa: RTOS used in Multimedia system such as video streaming application
For instance, in video streaming, a slight delay in displaying a frame might result in a minor stutter, but the system can still function and continue to deliver video.
Firm RTOS
RTOS of this type have to follow deadlines as well. In spite of its small impact, missing a deadline can have unintended consequences, including a reduction in the quality of the product. Example: Multimedia applications
Embedded RTOS
RTOS of this type is designed to run on embedded systems, which have limited resources. Deadlines may not be strict. It is used in IoT devices, smart consumer appliances.
Example: FreeRTOS, Zephyr
Real-time RTOS examples
ECU:
A classic example is an engine control unit (ECU) in a car, where the RTOS ensures Tasks like fuel injection, spark timing, and emissions control happen at precise moments, even when interacting with external events like the driver pressing the accelerator.
Medical devices:
In pacemakers, the RTOS guarantees real-time responses to ensure patient safety and in aircraft flight control systems, it manages critical functions with millisecond
Precision.
Robotics:
RTOS is used in robotics for precise motion control, sensor data processing and
Communication.
Air Traffic Control:
RTOS is used in air traffic control systems for real-time monitoring
and decision making.
