Two of the most important assemblies for the majority of managed applications are
System. Rarely does any application not touch functionality defined in one of those assemblies. The distinction between both is mostly a matter of logistics, reflecting how the framework and runtime designers decided to split up things.
mscorlib doesn’t appear in the References section in Visual Studio, even though it’s being referenced by the compiler. The philosophy behind this is that a whole bunch of types defined in the
System namespace live in
mscorlib and are required to write C# applications. For example, because
System.Object is used as the base class for every type, the compiler needs to be able ...