The Microsoft Windows Driver Kit (WDK) contains all of the header files (.h files) that you need to build kernel-mode and user-mode drivers. After you have installed the WDK, you can find the header files under the \inc subdirectory.

Starting with the Windows Vista version of the WDK, the following changes have been made to the content, structure, and organization of the WDK's kernel-mode and user-mode header files:

• Header files contain version information.

  By including version information in header files, the WDK enables a single set of header files to support development of drivers for multiple operating system versions, even though header file contents differ among the versions.

• Some header files are hierarchical.

  Files that are higher in the hierarchy include files that are lower in the hierarchy. Specifically, Ntifs.h includes Ntddk.h, which includes Wdm.h. This hierarchy eliminates the duplication of contents that occurred when the files were not hierarchical.

• The header file directory tree has been simplified.

  Header file versioning and hierarchical files have made it possible to simplify the directory structure that the WDK uses for header files.

The following topics describe the header file changes and how the changes affect developers who write drivers for Windows: