Framework Class Library

The Framework Class Library (FCL) is a standard library and Microsoft's .NET Framework implementation of the Standard Libraries as defined in the Common Language Infrastructure. The FCL is a collection of reusable classes, interfaces and value types. The Base Class Library (BCL) is the core of the FCL and provides the most fundamental functionality, which includes classes in namespaces System, SystemCodeDom, SystemCollections, SystemDiagnostics, SystemGlobalization, SystemIO, SystemResources and SystemText.