With Windows 10, Microsoft announced (and repeatedly renamed) its new Universal Windows Platform. UWP incorporates WinRT but goes beyond, as David Hale says in this MSDN article:
Windows 10 introduces the Universal Windows Platform (UWP), which further evolves the Windows Runtime model and brings it into the Windows 10 unified core. As part of the core, the UWP now provides a common app platform available on every device that runs Windows 10. With this evolution, apps that target the UWP can call not only the WinRT APIs that are common to all devices, but also APIs (including Win32 and .NET APIs) that are specific to the device family the app is running on. The UWP provides a guaranteed core API layer across devices. This means you can create a single app package that can be installed onto a wide range of devices. And, with that single app package, the Windows Store provides a unified distribution channel to reach all the device types your app can run on.
All of the UWP programs are destined for the Windows Store -- at least that's what we're supposed to expect. But take a look at what's happened, what's available in the Windows Store now. Microsoft originally put Metro apps in the store, then WinRT apps, and now UWP apps, and the pickings are embarrassingly slim.
We have a handful of Windows Store/WinRT apps from Microsoft: OneNote, Sway, and arguably Maps are ready for prime time. Then there's all the rest: Edge, which is only now starting to sprout extensions; the recently announced rework of Skype; and the almost-promised working version of OneDrive (see the screenshots onThurrot.com). Microsoft has been working on these big apps for more than a year -- nearly two years on Edge -- and they're shadows of what they should be by now.
Microsoft itself is shunning the platform. The severely stunted Office Mobile is still around, but Office itself doesn't run on WinRT. The built-in Windows 10 apps are, with few exceptions, stick figures of real apps and don't cover many basic features. The WinRT Mail app, for example, is only now getting the ability to pop out messages, fer heaven's sake. WinRT Photos (the Windows 10 Photos app) doesn't hold a candle to Google Photos. And so on.
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