Specifications

4-135
Printer, Plotter, and Spooler Subsystem Programming
The _d attribute in a virtual printer definition (a digested colon file) specifies the input data
stream type for the queue associated with that virtual printer. The virtual printer definition
also specifies the formatter filter for that input data stream type. When the formatter filter is
invoked to process a job, the process that runs the formatter (pioformat) filter checks the
value of the _d attributes and decides whether to invoke the formatter filter in pass–through
mode. If pass–through mode is selected, the formatter filter uses the passthru() subroutine
to read the input stream and send it unmodified to the printer device driver. If pass–through
mode is not selected, the formatter filter uses the lineout subroutine to process the input
data stream line by line. In either case, the printer device driver was opened for writing in
pass–through mode and performs no processing on the output data stream.
Note that input data streams such as PostScript are pass–through by definition; the
processing is performed by the Postscript interpreter hardware on the printer.
Most of the printer device driver parameters that one can display or modify using the splp
command also exist in the formatter filter. These parameters are stored in the digested
version of the colon file for a given virtual printer. For example, the mapping between the
printer device driver parameters and the corresponding parameters in the colon files for an
ASCII queue on an IBM 4029 LaserPrinter is as follows:
pass–through?
–p _d
page length (lines) –l _l
page width (columns) –w _w
indentation (columns) –i _i
wrap long lines? –W _L
convert to uppercase? –C N/A
send carriage
returns?
–c _x
send linefeeds ? –n _x
carriage rtn after
linefeed
–r _x
suppress tab
expansion?
–t N/A
send backspaces? –b N/A
send formfeeds? –f _Z
The values of the parameters in the right column can be permanently set in the virtual
printer definition. They can also be overridden at the time a job is submitted by using certain
flags on either the qprt or enq commands.