Microsoft's Windows 10 OS has reportedly been installed in 600 million devices worldwide. Windows 10, which was launched back in 2015 and geared towards PC's 2-in-1's, xBox and mobile phones has predominantly been available for free on older devices and offered as a free upgrade. Microsoft's bailing out on their mobile platform has somewhat impacted the company's initial target of seeing Windows 10 on 1 billion devices.
Windows 7 is still the dominant operating system in use with a 46% market share while Winows 10 is climbing up the rungs with 27% market share.