Windows Native API

This article relies excessively on references to primary sources. Please improve this article by adding secondary or tertiary sources. Find sources: "Windows Native API" – news · newspapers · books · scholar · JSTOR (January 2018) (Learn how and when to remove this message)

The topic of this article may not meet Wikipedia's general notability guideline. Please help to demonstrate the notability of the topic by citing reliable secondary sources that are independent of the topic and provide significant coverage of it beyond a mere trivial mention. If notability cannot be shown, the article is likely to be merged, redirected, or deleted. Find sources: "Windows Native API" – news · newspapers · books · scholar · JSTOR (February 2022) (Learn how and when to remove this message)

The Native API is a lightweight application programming interface (API) used by Windows NT's kernel and user mode applications. This API is used in the early stages of Windows NT startup process, when other components and APIs are still unavailable. Therefore, a few Windows components, such as the Client/Server Runtime Subsystem (CSRSS), are implemented using the Native API. The Native API is also used by subroutines such as those in kernel32.dll that implement the Windows API, the API based on which most of the Windows components are created.

Most of the Native API calls are implemented in ntoskrnl.exe and are exposed to user mode by ntdll.dll. The entry point of ntdll.dll is LdrInitializeThunk. Native API calls are handled by the kernel via the System Service Descriptor Table (SSDT).