Microsoft's One Windows strategy is only causing confusion because we seem to have forgotten what an operating system is.
Microsoft CEO Satya Nadella laid out very clearly on the Microsoft earnings call what the strategy is for Windows, which is to "consolidate overlapping efforts. This means one OS that covers all screen sizes".
He even repeated it; "one, single converged operating system for screens of all sizes".
That's one OS, built by one OS team, for multiple different systems. What's 'one' about that?
Nadella talked of one team with a layered architecture which allows it "to scale the UI across all screen sizes. It allows us to create this notion of universal Windows apps and bring coherence there."
But it's only clear if you're clear on what an operating system is; it's not just the kernel and it’s certainly not just the desktop, and it doesn't run on only one kind of processor.
One Windows isn't just the 'three screens and a cloud' strategy of different devices that might share interface elements or let you use the same account, or have a little bit of Windows inside. That's old Microsoft, many-Windows Microsoft.
At one point, Azure was a fork of Windows with a very different hypervisor; now it's the same OS as Windows Server, with the same Hyper-V hypervisor. But you couldn't take the Azure OS code, put it on a single Xeon server and do anything useful with it because it's designed to do something specific - run a cloud service.
Windows Phone 8 uses the NT kernel, but it isn't the same OS as Windows 8; not only is the user experience very different but it has different runtimes and (unless you're Microsoft porting across Internet Explorer), you can't build an application that runs on both. Windows Phone 8.1 is closer; it has the WinRT runtime and the concept of universal apps, with the Windows Phone Store and Windows Store being the same underneath. Over 90 percent of the API's are shared between Windows 8.1 Update and Windows Phone 8.1.
This what executive vice president of the Operating Systems group Terry Myerson talked about last December and it's the same One vision of Windows that's been the plan since the One Microsoft re-org. "We want to have one platform that powers all of our devices," Myerson said at the Credit Suisse technology conference, "so that developers can really target the aggregate scale of Microsoft with their investments."