What are real-time operating systems?

What are real-time operating systems ? Let's pay attention to a detailed study of the RTOS. First of all, these are special types of operating system that differ from universal OS with their performance and speed in the worst situations. There are many concepts that reveal the specifics:

- RTOS is a system that can provide the necessary service for a certain period of time;

- a real-time system that is characterized by constant availability and the time of the processed information is invisible to users;

- "fast system", where the first time is not the response time of the RTOS, but the time enough to work with the application.

For completeness, it is worth paying attention to the characteristic features of real-time operating systems. The most important feature is a guaranteed and stable reaction to the events taking place. Tasks of any level (high and low priority) should not conflict with each other and displace each other. High level of requirements to the response time to a certain event in real time.

Types of real-time operating system

Separate them depending on the programs: hard (hard), soft (soft) and interactive. Let's briefly review each species.

Rigid RTOS have a strictly defined response time to the event in real time. Example: hardware interrupt, display of control commands should be processed for a certain time, which happens in 100% of cases.

Soft real-time systems allow in 80-90% of cases to deviate from certain time frames by one order. But the main thing is that these delays do not lead to irreparable consequences.

Interactive RTOS includes the human factor (when the individual expects a response from the system after the instructions or commands given to them).

The most common real-time operating systems and their characteristics

Most RTOS is a closed type, and it is difficult to obtain detailed information about them. WindRiver Systems has developed VxWorks (a rigid RTOS) for software development on embedded PCs. It is based on the work of the host computer on which the software is developed and the client computer, where it is used for VxWorks management.

These real-time operating systems are widely configurable, but software modules can not be used in another environment, which makes them rather limited in use. The advantages include:

- Unlimited number of tasks to be solved.

- The number of priority tasks is up to 256.

- Tasks are planned cyclically or by priorities.

- Semaphores that help manage critical system resources.

Real-time operating systems QNX Neutrino Realtime Operating System is the brainchild of QNX Software Systems. It is based on a cross-server architecture and is characterized by great multitasking with a priority mode. Each element of the system works independently: in case of failures and failures, any link can restart itself without affecting the operation of the kernel or other components. It also has a deep configuration, a binding to the core kernel, which excludes work in another environment.

ChorusOS is an example of an embedded OS, which is widely used in telecommunications. It supports various telecommunications protocols, Java-technologies, which allows the introduction of new developments and applications.

Difference from the OS of general use and destination

The RTOS differs from general-purpose systems by the deterministic nature of the work, which is determined by the strict control of time spent on processing tasks. The term "determinism" describes a predefined time interval for which a single real-time program runs.