What app architecture did Windows 8 introduce for Store apps?

Windows 8 introduced Windows Runtime, or WinRT, as the app architecture for its new generation of Windows Store apps. It provided APIs and components intended for touch-friendly, sandboxed applications distributed through the Windows Store.

WinRT was built on Microsoft's COM technology and designed to be consumed by multiple programming languages, including C++, C#, Visual Basic, JavaScript, and HTML5. Its metadata system helped languages work with the same APIs, while its asynchronous design supported responsive apps during tasks such as networking or file access.

WinRT was not simply a replacement for every Windows program. Traditional desktop software continued to use Win32, and Windows RT imposed stricter compatibility limits because it ran on ARM hardware. The architecture later evolved into the Windows Runtime APIs used across newer Windows app platforms.