How is a C# program compiled to a processor specific native code?

When C# programs are compiled, they are physically packaged into assemblies. Assemblies are self-describing unit of functionality containing both code and metadata. Assemblies typically have the file extension .exe or .dll, depending on whether they implement applications or libraries.

Assemblies contain executable code in the form of Intermediate Language (IL) instructions, and symbolic information in the form of metadata. Before it is executed, the IL code in an assembly is automatically converted to processor-specific code by the Just-In-Time (JIT) compiler of .NET Common Language Runtime.