QNX Neutrino RTOS (also "QNX6") is a RealTimeOperatingSystem which looks a lot like UNIX, and runs on PC hardware.  It has a really nice GraphicalUserInterface (Photon), and will also run most UNIX software, like X11 and such.  For a while, they were distributing a full-blown OS+GUI+MPEG Player demo version that fit on a single bootable floppy!

http://www.qnx.com, if you want to take a looksee. http://www.openqnx.com if you want to join the QNX community.

See MicroKernel.
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CategoryOperatingSystem