Real-Time Operating Systems

Real-Time Operating Systems

Another kind of operating systems is the real-time system. These systems are characterized by having time as a key parameter. For instance, in industrial process control systems, real-time computers have to collect data about the production process and use it to control machines in the factory. Often there are hard deadlines that must be met. For instance, if a car is moving down an assembly line, certain actions must take place at certain instants of time. If a welding robot welds too early or too late, the car will be ruined. If the action absolutely must take place at a certain moment (or within a certain range), we have a hard real-time system. Many of these are found in industrial process control, avionics, military, and similar application areas. These systems must provide absolute guarantees that a certain action will occur by a certain time.

Another type of real-time operating systems is a soft real-time system, in which missing an occasional deadline, while not desirable, is acceptable and does not cause any permanent damage. Digital audio or multimedia systems fall in this category. Digital telephones are also soft real-time systems.

Since meeting strict deadlines is critical in real-time systems, sometimes the operating system is merely a library linked in with the application programs, with everything tightly coupled and no protection between parts of the system. An example of this type of real-time system is e-Cos.

The categories of handhelds, embedded systems, and real-time systems overlap significantly. Almost all of them have at least some soft real-time features. The embedded and real-time systems run only software put in by the system designers; users cannot add their own software, which makes protection easier. The handhelds and embedded systems are intended for consumers, whereas real-time systems are more for industrial usage. However, they have a certain amount in common.


operating system, software, real-time system