the Xbox. Most explicitly, Nadella said in July that Microsoft will unify its platforms "into a single, converged [OS] for screens of all sizes."
4. Threshold will run differently on different devices.
As Nadella's July quote might indicate, many commentators expect Microsoft to stop differentiating among different Windows variants once Threshold hits; that is, rather than having multiple OSes for multiple device types, Microsoft will have one version of Windows that detects what kind of device it's running on and automatically loads the appropriate UI. For PC users, Threshold will default to a "traditional" experience designed around mouse-and-keyboard use -- but with optional features for Live Tiles and touch. Tablets and phones, on the other hand, will load a next-gen version of Windows 8's tiled Start screen. Hybrid devices such as the Surface Pro 3 will act somewhat as they do today, giving users the option to switch between UIs.
5. Threshold is also expected to include Internet Explorer 12 and virtual desktops.
Internet Explorer 12 (IE 12) is expected to debut as part of Threshold, though the next-gen browser doesn't appear to be present in the recently leaked build. Not much is known about the next version of IE, though some reports claim it will include both a visual makeover and better support for extensions.
6. The Threshold desktop won't include Charms.
The Charms menu was among Windows 8's most-criticized elements. Because it was invisible until swiped or moused into view, many users felt the menu hid essential functions, such as printing or sharing content within a Modern app. With Threshold, Microsoft will reportedly remove Charms from the desktop. It's not clear if Charms will remain in Threshold's tablet and smartphone UI. It's also not clear if Charms will be present in the upcoming preview; the Charms removal will require some functionality to be integrated into Modern apps themselves, but because most app makers haven't had time to update their offerings, the preview might include Charms for continuity.
7. This month's Threshold preview might be one of many.
September's event is expected to focus on Threshold's desktop UI and enterprise customers; it is not expected to address changes Threshold will bring to smartphones and tablets. Microsoft will reportedly release a second, consumer-oriented preview in early 2015 that will focus on ARM tablets and smartphones. Microsoft will also allegedly launch a preview of the Threshold version of Windows Server, possibly as soon as this month.
8. Threshold could evolve significantly between the preview and its final release.
Microsoft is expected to release the final version of Threshold in spring 2015, but the OS could still change significantly before that happens. According to reports that were subsequently corroborated by the leaked videos, the preview will include a Live Tile that lets users easily submit preview feedback to Microsoft. Different users could be given different versions of the preview depending on the feedback they provide, presumably so Microsoft can tune its new OS to user preference as much as possible.
9. Windows Threshold might not be called Windows 9.
There are two schools of thought regarding whether Threshold will hit the market as Windows 9, or as just Windows. The former assumes Microsoft should use Windows 9 in order to distance its next OS from Windows 8's poor reputation. The latter stems from Microsoft's recent declaration that it will deliver Windows features via monthly updates rather than through the large feature packs it has historically released every few years. There's evidence to support both lines of speculation. A reference to Windows 9 popped up in a social media post from an official Microsoft account, for example; Microsoft declined to comment on the post, which was quickly deleted. Then again, the leaked build contains many references to "Windows" but none to "Windows 9." For the last year, Microsoft's advertising has also emphasized "the new Windows" rather than "Windows 8.1."
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