Browse Prior Art Database

Using Device Names to Dynamically Switch Printer Data Streams

IP.com Disclosure Number: IPCOM000100996D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 123K

Publishing Venue

IBM

Related People

Bushaw, KA: AUTHOR [+3]

Abstract

Many printers can accept several printer data streams. For example, the IBM 4216-020 Personal Pageprinter can accept PostScript*, PCL, and the Proprinter XL data stream. Such "multi-stream" printers allow customers a wider range of supported applications than printers that accept only one data stream. However, most applications and operating systems do not recognize the possibility that a single device can accept more than one type of data. It is usually assumed that if several data streams are being used, there are several devices.

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This is the abbreviated version, containing approximately 52% of the total text.

Using Device Names to Dynamically Switch Printer Data Streams

       Many printers can accept several printer data streams.
For example, the IBM 4216-020 Personal Pageprinter can accept
PostScript*, PCL, and the Proprinter XL data stream.  Such
"multi-stream" printers allow customers a wider range of supported
applications than printers that accept only one data stream.
However, most applications and operating systems do not recognize the
possibility that a single device can accept more than one type of
data.  It is usually assumed that if several data streams are being
used, there are several devices.

      To understand the problems that assumption can cause, consider
the applications of Fig. 1:  Application A outputs PostScript to the
printer via a standard device driver and Application B outputs PCL to
the same printer through the same device driver.  The customer
configures the printer to accept PostScript and begins using
Application A.  If the customer now prints from Application B, the
printer interprets the PCL data stream as if it were PostScript and
an error occurs.  To properly print from Application B, the customer
must first reconfigure the printer to accept PCL.

      To reconfigure the printer to accept a different data stream,
many printers use switches or the printer operating panel to define
the printer data stream.  These printers require the user to flip
switches or to press a series of buttons on the printer in order to
move between Application A and Application B.  Such manual
intervention is unacceptable for an unattended printer attached to a
Local Area Network.

      In some printers, the customer can send the special printer
control signals specifying "Switch to PCL," "Switch to PostScript,"
etc.  No physical switch is required.  If each print job begins with
a "Switch to XXX" control, print jobs for all data streams can be
interleaved without error and without customer intervention.  Many
applications allow the customer to specify a "setup string" that is
inserted at the start of each print job.  If the customer defines the
setup string for each of his applications to be the appropriate
"Switch to XXX" control, he can interleaf the print jobs without
error.

      Applications that do not include a setup string cannot use the
preceding method.  Fig. 2 illustrates a solution.  A user-defined
device name is created for each of the printer data streams.
Customers output PCL to a device named, for example, PCL_PRT and
PostScript to PS_PRT.  The device driver inserts the appropriate
"Switch to XXX" control message before each print job, based on the
name of the device.

      In addition to inserting the "Switch to XXX" controls, the
dynamic switch driver can perform complicated stream-switching
processes that would be difficult without the drive...