unmanaged resource

Question

As all of you know that operating system file and network connection all are unmanaged resource can anyone tell me that why these are unmanged how we can decide that this is managed and this is unmangaed or CLR will decide this.

Answer

Any application that runs/executes under the Common Language Runtime (.NET Framework) is said to be a managed application. This doesn't mean that .NET applications can't use the Unmanaged resources. Like for e.g. a COM component can be easily used in a .NET application. This happens in background with the help of the RCW(Runtime callable Wrapper), which marshals calls between the .NET code to the Unmanaged COM component.
Ultimately every code whether managed/unmanaged gets converted to the native code.