Windows NT Print Driver Architecture

MORE INFORMATION

Printer drivers are composed of three separate files:

1. A printer graphics driver (for example, PSCRIPT.DLL, RASDD.DLL, or PLOTTER.DLL). Graphics drivers are responsible for print rendering (converting DDI commands from the graphics engine into printer commands that a printer can understand). Each graphics driver handles different printer languages. For example:
   

         PSCRIPT.DLL: deals with the PostScript printer language.
         PLOTTER.DLL: deals with the HPGL/2 language used by many plotters.
         RASDD.DLL:   deals with printer languages based on raster (bitmap)
                      images, including PCL and most dot matrix printer
                      languages.

2. A printer interface driver (for example, PSCRPTUI.DLL, RASDDUI.DLL, or PLOTUI.DLL). This dynamic-link library (DLL) includes the user interface you see when you configure a printer in Print Manager. It is called by the client side of the router (WINSPOOL.DRV).
3. Characterization Files: Characterization data files provide model- specific information about print devices.
   
   When hardware vendors release new print devices, a characterization data file for the new device is all you will need for Windows NT. If Windows NT does not supply such a file for your print device, check the device's users' guide for a list of emulations. If your device emulates a device for which Windows NT supplies a driver, then you may be able to use this driver to get output.
   • Raster minidrivers are actually DLLs. The Windows NT Raster printer driver can read most Windows 3.1 minidriver DLLs (those created for UNIDRV.DLL)directly with no porting required. Raster minidrivers contain printer-specific information.
   • The PostScript driver uses standard Adobe PostScript .ppd files as characterization data files. These files include printer-specific information for a particular printer model and are available from the printer's manufacturer. Unlike Windows 3.1, the Windows NT PostScript printer driver can directly interpret .PPD files. Because PostScript printers are included with .PPD files, when new PostScript printers become available, they will be ready for use with Windows NT.
   • Plotter .pcd files are similar in function to raster minidrivers. They are dynamic link libraries (DLLs), which provide device-specific information to the graphics driver. Unlike raster minidrivers, .pcd files are specific to Windows NT; Windows NT cannot use plotter drivers built for Windows 3.1.

The architecture explained above is an excellent way to easily support a variety of printers by using a characterization file. The disadvantage is that new innovative technologies or unique vendor-specific features are not always supported by the universal driver. For this reason it is often a good idea to request a vendor-supplied NT Print driver to fully utilize the capabilities of a print device.