Native API

The Native API (with capitalized N) is the application programming interface (API) used by Windows NT and user mode applications. It is usually used during system boot, when other components of Windows are unavailable, and by routines such as those in kernel32.dll that implement the Windows API. The entry point of ntdll.dll is LdrInitializeThunk. Most of the Native API calls are implemented in ntoskrnl.exe and are exposed to user mode by ntdll.dll. Some Native API calls are implemented in user mode directly within ntdll.dll.