Assemblies contain tables of metadata. These tables are described by the CIL specification. The metadata tables will have zero or more entries and the position of an entry determines its index. When CIL code uses metadata it does so through a metadata token. This is a 32-bit value where the top 8 bits identify the appropriate metadata table, and the remaining 24 bits give the index of the metadata in the table. The Framework SDK contains a sample called metainfo that will list the metadata tables in an assembly; however, this information is rarely of use to a developer.
In the past, a software component (.exe or .dll) written in one language could not easily use a software component written in another language. COM provided a step forward in solving this problem. The .NET Framework makes component interoperation even easier by allowing compilers to emit additional declarative information into all modules and assemblies. This information, called metadata, helps components to seamlessly interact.
The Common Language Specification (CLS), which is a set of basic language features needed by many .Net applications to fully interact with other objects regardless of the language in which they were implemented. The CLS represents the guidelines defined by for the .NET Framework. These specifications are normally used by the compiler developers and are available for all languages, which target the .NET Framework.
