QNX
Unix Operating System

INDEX Introduction I. General Structure : the Microkernel – The Key Element A. IPC:InterProcess Communication B. Scheduler Process Manager Device Manager Filesystem Manager Network Manager Photon

II. III. IV. V. VI. Conclusion References

QNX -Unix Operating SystemQNX was born in 1982, from the hands and the brains of two Waterloo university students Dan Dodge and Gordon Bell. It is a Real Time Operating System. Elaborated on an UNIX structure, it is used in the software development, the control of industrial robots, and in onboard computers. Stable, ergonomic, safe and fast and is known for its very high uptime, it knows a good fault tolerance. Moreover the preemptive multitasking and the Memory Protection Runtime make it a stable basis for development for many uses.

I.

General Structure : the Microkernel - The Key Element

QNX uses a microkernel which allows to operate the global system as a set of little tasks, called “servers”. By this way, the whole system runs around the kernel as we can see in the following schema:

Schema 1

The microkernel is divided in 4 parts: Two big:  IPC  Scheduler  Network Interface  Interrupt Director

Two small:

Let’s interesting to the two most important: A. IPC : InterProcess Communication This is the processes which transmit together. It supports 3 essential types of IPC: Messages, Signals, and Proxies.  Messages: they secure synchronous communication between cooperating processes where the process sending the message requires proof of receipt and potentially a reply to the message. Processes are only generally "die" after receiving a signal, but they can also ignore it.

 Signals: used to support asynchronous interprocess communication. These are packets of data. (Packages are used because the CPI may be both locally on the machine and on the network). When the process wants to send data, it sends it to another process and hangs the sends until the other process