Today's Windows 10 Desktop preview is the second Microsoft has made available to testers in March, and the fourth Windows 10 Desktop build the company has released as of October 1, 2014.
Like Windows 10 Desktop -- which runs on PCs, laptops and tablets -- Spartan is still not feature-complete at this point. The first Spartan preview does, however, include most of the functionality that Microsoft execs showed off on January 21 during an early demo of Spartan as part of a Windows 10 press event.
Specifically, the integration between Spartan and Cortana, Microsoft's personal digital assistant, is in today's Windows 10 release, as is the "Ask Cortana" user assistance technology. The ability to annotate Web pages with a pen or mouse is included in today's Spartan build. Users can share annotated Web pages using this new "Web Note" technology and view the annotated pages in a variety of browsers.
The new Reading View, which allows users to view content with fewer distractions and/or save it for later, also is in Spartan in today's new test build. (The ability to read saved content offline is not yet enabled in today's test build.)