Review Take a deep breath. This is it, the big one: Microsoft has released Windows 10, which will make everything good again after Windows 8.
Windows 10 is distinctive for several reasons. First, it introduces the "Windows as a service" concept, in which most users will automatically receive incremental updates with both feature and security patches. Second, it is a free upgrade for most existing users of Windows 7 or 8.1. Third, it is a multi-device operating system that runs on PCs, tablets, phones, HoloLens-augmented reality headsets, and miniature computer boards like Raspberry Pi.
These various editions are unified by an application runtime called the Universal Windows Platform (UWP), which enables developers to code apps once and have them run on all the above devices as well as Xbox One. Different display sizes are catered for by a mechanism called the Adaptive UI, where the user interface adapts itself automatically to the size and orientation of the screen. UWP apps are deployed through the Windows Store, now unified across phone and PC, and users can buy an app once and run in on a variety of devices.
Windows 10 is not Microsoft's first attempt to create an operating system that runs well on tablets as well as PCs. Earlier efforts include the 2002 Tablet PC, based on Windows XP and adding pen support, handwriting recognition, and voice input. In November 2001, then-CEO Bill Gates said that "I'm already using a Tablet as my everyday computer... within five years I predict it will be the most popular form of PC sold in America." Tablets were indeed a success, but not until April 2010 when Apple released the iPad. Pens are an expensive nuisance for most users, and traditional Windows applications are ill-suited to control with touch.
Windows 7 had support for touch input built in, but Microsoft saw that it could not compete with the iPad without radical changes. Windows 8 introduced a touch-friendly environment (known as Metro) and a new Windows Store that enabled users to install and remove applications with iPad-like simplicity. Under the covers, an application platform called the Windows Runtime isolated apps from each other and from the operating system, improving security and preventing the install of one app from breaking another.
These were good things; but the changes and the way they were introduced went down badly with users, who disliked the jarring effect of jumping between Metro and desktop Windows and missed the Windows 7 Start menu. The problem was compounded by a lack of worthwhile apps to install. Many users, including most businesses, stuck with Windows 7.
The new deal
The Windows 10 team discarded the Metro environment but retained the Windows Runtime and Store. The new concept is that all apps run on the desktop, though there is an optional "Tablet mode" in which apps run either full screen or in a two-to-view split view, making the desktop invisible. The Windows Store is therefore now on the desktop, and Microsoft CEO Satya Nadella has stated that winning greater visibility for the Store is a core goal.
The company is making a huge push for Windows 10, driving upgrades from Windows 7 or 8.1 through Windows update for eligible users. Users who accept the invitation to "Get Windows 10" will be prompted to initiate an in-place upgrade. It is a high risk strategy, partly because in-place upgrades are more error-prone than clean installs, and partly because Windows 10 is so new, but reflects Microsoft's determination to shift its user base rapidly.