I remember running a QNX OS demo in the late 90's or early 00's that ran live off a floppy disk.. (with full GUI and everything) this was a big deal at the time. I was amazed.
I tried that, too - QNX RTOS 4 or something like that. As an OS with a shell and a full GUI, it was quite impressive for the tiny binary!
I used to run that, too! Not only with a GUI, it also had a web browser and could use many modems. I was also amazed.
They still teach realtime systems with this version of QNX at my old university (University of New Brunswick). We also use it to drive a National Instruments DAC/ADC board.
Funny I was just telling a friend about QNX today.