Printer drivers differ from the typical display driver in that device-specific information can be obtained and altered via the user interface. Through the Win32 Printer Folder in the Windows NT interface, the user has access to view and alter certain printer properties such as the name of the printer, which port it connects to, and which paper trays are used. Furthermore, many applications allow modifications to the printer setup for a particular document.
To accommodate this functionality, printer drivers must provide a printer interface DLL that includes functions for setting printer properties and document properties by the adminstrator/end-user. This printer interface component is in addition to the printer graphics DLL required for rendering the image to be printed.
Note that where the printer driver is loaded and executed in Windows NT system memory, the printer interface driver is a user-mode module that is loaded and executed in the context of the spooler.
Sample code for the printer interface component of the printer driver can be found in the psui directory of the Windows NT DDK.