That's completely, utterly untrue.
QNX does indeed sport paged-virtual memory with memory protection;
(although QNX4 does not support swap).
User-mode interrupts are standard procedure; the deadlock problems
Alan has mentioned do not apply, since any running process is
always resident in memory.
Shared regions have to be explicitly created; access is *not* open
Nothing has to be known at "compile time"; QNX is a full-featured
OS with dynamic loading.
> Therefore, any piece of code can do anything it wants including
> handling hardware directly.
Again not true; only privileged processes can enter kernel mode
to execute port I/O instructions directly.
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