Microsoft's major update to its operating system, called Windows 10, has been built to blend old and new in a way that will be familiar to Windows 7 users while also retaining much of its more modern tile interface.
The new OS will run on all hardware devices when it ships next year, from phones to tablets and desktops, and provide software developers with a way to write applications that can span all those platforms, the company said.
The logical name for the OS would be Windows 9, but Microsoft jumped to Windows 10 to reflect what it sees as a big break from the past.
"Because we're not building an incremental product, the new name will be Windows 10," Terry Myerson, executive vice president of the Operating Systems group, declared at a launch event in San Francisco, where he showed some early code.
The event on Tuesday was aimed at enterprise users, who have been most critical of the jarring UI changes that came with Windows 8. A big theme was that the new OS will be accessible to users who are familiar with older operating systems, but still include aspects of the modern interface in Windows 8.
For instance, the desktop OS has a start button at bottom left which opens a split menu -- to the left is a Windows 7 style menu including the familiar apps and tools, and to the right are "live tiles" that allow users to open more modern "metro" style apps. Users can drag and drop those live tiles to customize that portion of the start menu.
Microsoft is promising a universal development platform for app developers, so that they can write applications that will run across all Windows devices. It will provide details at its Build conference next year.
"There will be one way to write a universal business app that targets the entire product family," said Joe Belfiore, corporate vice president of the Operating Systems group.
There will also be a single Windows apps store for all device types, one that businesses will be able to customize for their employees.
Microsoft is promising to make managing Windows devices easier. "Windows 10 will be compatible with all the management systems in use today," Myerson said.
For security, Windows 10 will have a "novel way" to separate corporate and personal data on devices, Belfiore said, though he didn't describe that in any detail.
Microsoft will start to distribute a "technical preview build" of the laptop and desktop versions of the OS this week, to be followed later by technical previews for tablets. The early code is designed for users who are "comfortable running pre-release software."
Early next year, it will say more about what consumers can look forward to, including new versions of apps like Internet Explorer. Today was about showing the basic user interface and what the OS means for enterprises.
The key message was that Windows 10 will be familiar to end users "whether they're coming from Windows 7 or Windows 8," as Myerson put it.
The new OS follows Windows 8, which was launched two years ago and largely failed to accomplish its mission: to improve Microsoft's position in the tablet OS market while retaining its dominance in PCs with substantial improvements for those users.
Windows 8 introduced a radically redesigned interface, called Modern, which was optimized for touch screen devices, like tablets, and an alternate Windows 7-like conventional desktop. But many found the OS inconvenient to use, particularly with mice and keyboards.
Enterprises felt particularly alienated by Windows 8 and its subsequent revisions -- Windows 8.1 and Windows 8.1 Update -- so it's not a coincidence that Tuesday's event focused on this customer segment and the particular concerns and needs of CIOs.
"Windows is at a threshold, and now it's time for a new Windows," Myerson said Tuesday.