.Net Framework
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Platform
The .NET Framework is a software platform for Windows. It is comprised of a "Base Class Library" and a "Common Language Runtime". The Base Class Library consists of pre-coded solutions to common program requirements, while the Common Language Runtime provides the appearance of an application virtual machine, so that programmers need not consider the capabilities of the specific CPU that will execute the program. It also allows software written in several languages to be run as one application.
An open-source alternative to the .Net CLR is Mono, which runs on Linux, Mac OS X, BSD, and Windows.