Print Processors and Data Types (104902)

SUMMARY

Windows NT and Windows NT Advanced Server both use print processors as part of the overall printing procedure. The main function of a print processor is to interpret what type of data is being passed from the spooler to the graphics engine. Windows NT includes WINPRINT.DLL as its only one print processor, which can interpret journal and raw data types.

MORE INFORMATION

Journal files are collections of Device Driver Interface (DDI) calls, which are precise commands specific to a particular hardware device. For example, a journal file created for a 150 dot-per-inch (dpi) LaserJet printer would not print properly on a 300 dpi LaserJet printer. Journal files can also contain TrueType font outline information, thus the destination printer need not have a particular font installed to render the print job. Journal files are processed, passed back to the spooler for routing to the graphics engine (GDI32.DLL), and then passed to the printer driver and finally sent to the output device.

Raw files need no processing from the print processor; they are handed to the spooler for routing to the graphics engine. An example of a raw data type is an encapsulated PostScript (.EPS) file because it needs no print processor interpretation or conversion.

Windows NT Advanced Server adds another print processor to the system: SFMPSPRT.DLL. This print processor interprets PostScript information passed from a Macintosh client and translates it to specific DDI commands that the Windows NT printer drivers can interpret. SFMPSPRT.DLL supports the PSCRIPT1 data type, which allows Macintosh clients to print PostScript files to raster printers.

Though its main job is to interpret compatible data types, the print processor also provides access to the printing process. You can modify the printing process by substituting a custom program in place of the Windows NT default print processor. A print processor could be used to filter data, to create a special dialog with the printer device, or to interpret a new data type. For example, you might have a print processor that filters ASCII for use on a PostScript printer.