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Print Processor

The print processor tells the spooler to alter a job according to the document data type. It works together with the printer driver to move the spooled print jobs from the hard disk drive to the printer. Localspl.dll is the print processor for all Windows-compatible printing; Sfmpsprt.dll is used to print to Apple devices.

Software vendors can develop their own print processors for custom data types. A printer vendor can also develop a custom print processor if the vendor has its own printer driver or supports a data type other than the five that Localspl.dll supports. Usually, the print processor is installed when the printer driver is installed.

RAW Data Type

For print jobs on computers that are not running Windows 2000 or Windows NT, the spool file's data type is RAW by default. These files are device dependent. The spooled data is destined and formatted for a particular device and does not need to be printed on a different device.

NT EMF 1.00x Data Type

With an EMF file, the GDI releases console control after generating it. The data is then interpreted in the background on a 32-bit spooler thread and sent to the printer driver. Splitting the rendering of a print job in this way is especially useful for very large documents, because the application is not tied up for the whole rendering time. The time gain is greatest if you have connected to rather than added the printer, because the background processing is done on the print server rather than the local computer.

EMF spool files are encoded to provide greater printer independence. For example, a graphic measuring 2 inches by 4 inches on a video graphics adapter (VGA) display and stored in an EMF maintains those dimensions whether it is printed on a 300-dpi laser printer or a 75-dpi dot-matrix printer. The EMF data type also ensures that the print server uses the fonts you specified.

TEXT Data Type

The TEXT data type allows you to send a simple-text print job to a print device (such as a PostScript device) that cannot interpret simple text. The spooler creates a new print job, embedding the text in print instructions derived from the print device's defaults for font, form, and orientation. The spooler uses the resolution setting specified using the Printing Defaults button on the Advanced tab in the printer's Properties dialog box.

Text files consist of ASCII characters. Several character sets are in common use, and text files do not indicate which one to use. The TEXT data type uses the American National Standards Institute (ANSI) character set, so it might print some characters wrong if the application uses a different set. Most character sets are identical for the values 0 through 127, so this problem usually affects only extended characters (values 128 through 255).

Windows operating systems use the ANSI character set. The default PCL character set is called Roman-8. PC-437 and PC-850 are commonly used by MS-DOS-based applications in the United States and Europe, respectively.

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