Xamarin.iOS is used to build apps for iOS with .NET and contains the bindings to the iOS APIs mentioned previously. Xamarin.iOS uses AOT compiling to compile the C# code into Advanced RISC Machine (ARM) assembly language. The Mono runtime runs alongside the Objective-C runtime. Code that uses .NET namespaces, such as System.Linq or System.Net, are executed by the Mono runtime, while code that uses iOS-specific namespaces are executed by the Objective-C runtime. Both the Mono runtime and the Objective-C runtime run on top of the X is Not Unix (XNU) Unix-like kernel (https://github.com/apple/darwin-xnu), which was developed by Apple. The following diagram shows an overview of the iOS architecture:





















































