Microsoft has shown off more features in the upcoming Windows 10 platform, including a version that will run on Windows Phone devices, universal applications, and Cortana coming to the PC.
Microsoft also said that Windows 10 will be offered as a free upgrade for the first year of its availability.
At an event in Redmond, Microsoft showed off more of the features coming in Windows 10, such as the cross-platform capabilities it has been promising to deliver the same experience across PCs, tablets and phones.
An updated Technical Preview build will be available next week for Microsoft's Windows Insider community of testers, the firm said, and the first build of Windows 10 for phones will arrive in February.
Microsoft also promised that Windows 10 will be available as a free upgrade for all devices running Windows 7, Windows 8.1 and Windows Phone 8.1 for the first year.
This is in order to get as many devices as possible upgraded to the new platform, according to Microsoft's executive vice president of its Operating Systems group, Terry Myerson.
"With our vendor partners, we're going to make Windows 10 the platform for the next billion customers," Myerson said.
Myerson was followed by Joe Belfiore, corporate vice president, of the Operating Systems Group at Microsoft, who showed off new capabilities in Windows 10, including the first demonstration of the platform running on a Windows Phone handset, in this case a Lumia 1520.
Belfiore said that Cortana is coming to Windows PCs, and will be available to testers on the Windows Insider programme over the next few months.
He also showed the Continuum feature that will optimise the user interface on devices such as two-in-one convertible tablets depending on whether a keyboard and mouse are attached or the user is just using a touchscreen.
Belfiore said that Microsoft is building a "family of universal apps" that will round out Windows 10 across phones, small tablets and PCs, which includes versions of Word, Excel and Powerpoint, plus the Outlook mail app.
These will not replace the desktop Office applications, but seem intended to complement them in a similar way to the desktop and Metro versions of OneNote that Microsoft already offers.
Microsoft also confirmed the much-rumoured new browser, codenamed Spartan, which features a new rendering engine and is "optimised for the way the web works today", according to Belfiore.
This includes a new reading mode offering a tuned reading experience, support for PDF document files, the ability to mark up web pages with comments and share or save them, and Microsoft's Cortana personal assistant technology built in to offer help when needed.
Microsoft did not make it clear, but it seems likely that Spartan will also complement, rather than replace, the desktop Internet Explorer.
Also coming to Windows 10 is a desktop Xbox app, enabling users to play Xbox entertainment titles on a PC.
Microsoft also showed a new device in the shape of the Surface Hub. This is a wall-mount 55in or 84in screen with a 4K display designed as a kind of Windows 10 intelligent whiteboard, running custom versions of Skype for Business and OneNote.
Perhaps the most impressive demonstration was saved for last. This was of the Microsoft HoloLens, a wearable device that looks like a chunky pair of spectacles and enables an augmented reality view of the world overlaid with digital images.
Microsoft confusingly refers to this as a holographic computing platform, because it enables solid-looking 3D objects to be added to the user's view of the world.
However, the demonstration Microsoft gave made Google's Glass device look primitive by comparison.
Windows 10 is still slated to ship sometime later this year, Microsoft said. More information is available on Microsoft's Windows Blog.
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