Sometimes it happens that a new version of an operating system introduces a new type of application completely incompatible with older versions of the same system. The last time it happened I think it was with Windows 95. More than 15 years later, Windows 8 comes with support for a completely new segment of applications named Windows Store apps.
These applications can only run on Windows 8 and they have a brand new look and feel compared to other and older Windows applications. In addition, Windows Store apps follow a different pattern as far as publishing and sales are concerned. Windows Store apps, in fact, can be distributed for free or for sale through a central marketplace known as the Windows Store. This channel is a valid alternative for widespread distribution to classic direct user-led install of applications.
Windows 8 specific applications are not limited to personal computers but can also run on a variety of compliant devices, most notably Microsoft Surface devices.
In summary, developers can now create two types of Windows applications: classic Window apps that also run on multiple and older Windows platforms (i.e., Windows 7, Windows Vista) and Windows 8 specific apps that only run on machines and devices equipped with Windows 8. Classic Windows applications can only be distributed manually or via custom setup programs; Windows 8 apps can be distributed via the public Windows Store or under the control of the system administrator.
Under the Hood of Windows Store Apps
All approaches deliver nearly the same programming power. This means that you can build the same application behavior regardless of the language and markup that you choose.
Figure 1: The Windows 8 runtime stack. Darker blocks refer to areas of the runtime covered in this article.
The WinRT API supplies several classes of functionality. In particular, you’ll find media, networking, storage and presentation functions.