User`s guide

2-4
Guide to Printers and Printing
• Receives from the qdaemon command a list of one or more files to be printed.
• Uses printer and formatting attribute values from the database, overridden by any flags
specified.
• Initializes the printer before printing a file.
• Provides filters for simple formatting of ASCII documents.
• Uses filters to convert the print data stream to a format supported by the printer.
• Provides support for printing national language characters.
• Passes the filtered print data stream to the printer device driver.
• Generates header and trailer pages.
• Generates multiple copies.
• Reports paper–out, intervention–required, and printer–error conditions.
• Reports problems detected by the filters.
• Cleans up after a print job is canceled.
• Provides a print environment that you can customize to address specific printing needs.
The mkvirprt command defines a virtual printer to the printer backend. The set of
predefined attributes for the particular type of printer is copied to create a customized set of
attributes. The customized attributes can be listed with the lsvirprt command and changed
with the chvirprt command or, by using the Devices or SMIT Change / Show Print Queue
Characteristics option. Each time the mkvirprt or chvirprt command is used, a digest
utility (piodigest command) is automatically run to construct a memory image of the
attribute values and lookup tables to be read in and used during the printing process.
The qdaemon command calls the piobe command (the Print Job Manager) and passes the
flag options and the names of one or more files to be printed. The only flag options not
passed are the spooler flag options removed by the enq command. The qdaemon
command has already opened the printer device and redirected standard output to the
printer. A status file provides communication between the qdaemon and the backend.
If a header page is needed, the piobe command retrieves a header page pipeline used to
generate the header page. The header page pipeline is passed to a shell. In the pipeline,
the standard output from the header page filter becomes the standard input for the formatter
filter. The formatter filter processes the header page and writes the result to standard
output. Standard output for the formatter filter becomes standard input for the device driver
interface program that writes the filtered header page to the printer device driver.
Formatter Filters
A formatter filter provides the capability of either formatting the input print file or passing it
through unmodified, based on an input parameter. Even if the formatter passes the input file
unmodified, it still sends printer commands to initialize the printer before the input file is
printed and restores the printer after printing is complete.
A formatter driver is device independent. There is a formatter for each type (or group of
types) of input data. For example, there is one formatter for all the supported Proprinters.