Windows Runtime Library

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What Does Windows Runtime Library Mean?

In the context of the Windows 8 operating system (OS), the Windows Runtime Library (WinRT) is the default application programming interface (API) used by the OS. It does not replace the Win32 API that has been running underneath all Windows applications, but rather augments it. WinRT is a C++ object-oriented API sitting at the same level as the Win32 API, not a shell that sits under Win32.


Techopedia Explains Windows Runtime Library

WinRT implements the Metro look that started in Windows Mobile 7. This brings a totally different look compared to the previous iterations of Windows. WinRT is an extensible application markup language (XAML)-based user interface (UI) system, which provides the same UI implementation to C++, HTML/JavaScript and .NET developers. This is totally unlike the Windows Presentation Foundation (WPF), which was only exposed to .Net and Silverlight (only exposed to browsers).

Even with the advent of WinRT, Win32 is not totally erased and both coexist. Developers have two options in development and users have these options as well. Users can install legacy system applications and Metro applications at the same time.

WinRT can be described as an API at the same level as Win32 that gives its applications the resources and functionalities they require. The only difference with Win32 is that WinRT is exposed to all application developers.

WinRT has the following properties:

  • All the parts of the API are designed to be asynchronous.
  • The API is sandboxed and designed for the easy creation of self-contained or app store-ready applications.
  • It exposes the WPF/Silverlight XAML UI model to developers.
  • The API definitions are in a metadata format, which is the same as the one used for .NET (ECMA 335).
  • It wraps both the Win32 API and the new UI system together.
  • It has a simple programming model for creating UIs. It is especially tailored for Windows developers who do not need to learn the Win32 API or terms like LPARAM or WndProc.
  • The Silverlight/WPF XAML UI model is exposed to developers.
  • It implements the look of Windows (formerly known as Metro)

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.