The QNX Neutrino RTOS architecture consists of the microkernel and some number of cooperating processes. These processes communicate with each other via various forms of interprocess communication (IPC). Message passing is the primary form of IPC in QNX Neutrino.
Figure 1. The QNX Neutrino architecture acts as a kind of "software
bus" that lets you dynamically plug in/out OS modules.
The above diagram shows an application sending a message to the GUI manager, and the GUI manager responding.