A fascinating little point made in a much longer piece about the smartphone wars. One that makes me wonder whether Unix can now be considered to be the most successful operating system of all time. Which is certainly a change from when I first entered the computing industry when Unix boxes were vast behemoths and the Windows based PC was what was used by the masses.
The point is made here:
“Within that, roughly 1.1bn had ‘smartphones’ at the end of 2012, of which around 900m ran either the iOS or Android versions of Unix. (As an aside, it is pretty striking that almost a fifth of the earth’s adult population has a Unix box in their pocket.)“

Apple’s iOS and Google’s Android are variations of Unix and with 900 million concurrent users it might indeed be the largest number of people using an operating system yet.

I agree that Windows sales numbers are, over time, much higher than of these Unix variants. So I agree that Microsoft has, over all the generations of Windows, sold more licenses but many of these licences are out of use.

My feeling is that Unix is indeed the world’s most successful operating system ever considering justthe two Unix variants, Android and iOS.
Add in all the servers used in the world at the same time plus All the TV’s that use Unix and the number is probably double the 900 million units. 1800 million concurrent users? I don’t think Windows will ever managed that because the currently installed and in use Windows systems is unlikely to be 900 million units, certainly not all operating at the same time. 

The growth rates are divergent, almost all tablets and smartphones now run some variant of Unix and those markets are still growing by leaps and bounds whereas the PC market is actually shrinking.