Quite a number of years ago, I was sifting through the links at a favorite website, fdisk.com, and came across QNX. It was described as a system-on-a-floppy. Now, an OS on a floppy was possible in the PC world. DOS could boot from a single floppy, and contain a few useable tools, and there were also some single-floppy Linux distros out there. QNX was different. It presented the user with a full GUI interface, with network support, a browser, editor, file manager, 3d graphics demo, terminal, and even a game. Pretty impressive at the time when Windows was growing to such huge proportions. You still might be able to find it today, but the drivers are a bit out of date. There are a couple of other projects today that are similar if you are interested, my favorite is MENUET OS, which is also a full GUI OS on a floppy, written entirely in machine code. QNX makes a full-blown version of their floppy OS for commercial use called Neutrino RTOS, mostly for embedded systems. It was fast, and stable. Perfect for kiosks and other public-facing applications that require long-term stability. A real-time OS (RTOS), is usually for use in embedded systems, robotics, research, and other applications where processing time can have an effect on final results, but makes for a snappy, reliable OS on the desktop too.
The reason I bring this up, is that QNX was purchased by RIM (Blackberry) recently and is this base OS for RIM's new tablet The Playbook. With such an efficient design, and 30 years of history behind it, QNX is a good solid choice for RIM to build on. I look forward to trying out the Playbook when it arrives. I also believe that RIM will build a version of QNX for their handsets too. The Java-based OS they currently use is long in the tooth, and not adapting well to the needs of smartphone users. Time will tell, but I think the rumors of Blackberry's demise have been greatly exaggerated.