Embedded Computer Systems Real Time Operating System Characteristics

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Real Time Operating System Characteristics


Real-time operating systems or RTOS are an important class of operating systems. Like all operating systems, RTOS can be examined from a variety of perspectives, including theory and actual implementation. An RTOS is defined as...:

"...the one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time at which the result is produced. If the timing constraints of the system are not met, system failure is said to have occurred."

Examining existing RTOS reveals how real-time systems are implemented. There are dozens of real-time systems available for different platforms. Many manufacturers simply state that their operating systems are real-time without explaining how this is accomplished. One real-time system, QNX, offers more insight, however. This operating system will be examined in detail to explain how real-time processing works.

QNX Real-time OS

The main responsibility of any operating system is to manage a computer's resources.

Some system processes call for strict resource management and scheduling. These processes depend on the OS to handle multiple events and to ensure that the system responds to those events within predictable time limits. The QNX philosophy is that the more responsive the OS, the more "time" a real-time application has to meet its deadlines.

QNX Software Systems Ltd develops real-time operating systems for personal computers. According to QNX:

"The QNX Operating System is ideal for real-time applications. It provides multitasking, priority-driven pre-emptive scheduling and fast context switching - all essential ingredients of a real-time system."


The heart of the QNX OS is the Neutrino kernel. It can be scaled to very small sizes with a fully functional core kernel of only 12K. The Neutrino kernel conforms to the POSIX-standard API. Neutrino is also remarkably flexible. It can...