Printer Driver FAQ

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Note: Unless you completely understand the technical issues involved, always select a PCL printer driver, as opposed to Postscript (PS), for any lab printer or plotter!!! Please read the following information for a light discussion of PCL, Postscript, and other printer languages.

Warning: In general, the use of Postscript drivers for lab printers and plotters (large-format printers) is unsupported as YMMV (Your Mileage May Vary) from what is expected. Furthermore, such print jobs may take quite a long time to process and may be cancelled at our discretion!

Q. What is a printer driver?

A. Most computer applications are not designed to interface directly with a printer. Instead, they are only able to produce an image to be printed, and must have assistance from the Operating System (e.g. Windows XP) to complete the task. In order to facilitate this process, the operating system supports a generic printing interface that may be extended with various "Printer Drivers" in order to support many different types of printers. It is imperative that one install the appropriate driver for a given device such that the printer receives accurate data.

Q. When selecting a driver, I see some of the following acronyms: PS, PCL, PJL, HP-GL/2, RTL, ESC/P, LIDIL, etc. For what do these abbreviations stand? Of what importance are they? What type of printer driver should I select?

A. These acronyms represent various printer "languages" - protocols by which a printer driver or application can instruct a printer to produce the desired output on paper. The following list defines and briefly explains each of these common abbreviations:

PS (Postscript)
Postscript is a language originally developed by Adobe in 1985 for the purpose of describing an image in a device independent manner. Over the course of time, it has received numerous revisions and now exists as the de facto standard for reproducing color-accurate documents. By design, the language extends itself to many different scenarios, and, consequently, boasts a degree of complexity which other languages have tried to avoid.
PCL (Printer Command Language)
Hewlett-Packard (HP) originally created the PCL in the early 1980's in an effort to provide an effective language for controlling a variety of printing devices, each having an unique feature set. The protocol has seen continuous development for more than two decades, and now commands more printers than any other language in existence. While not designed for the highest possible color accuracy (e.g. it lacks Pantone support), receiving devices can quickly process the print job and greatly reduce the amount of time required for printing when using the PCL.
PJL (Printer Job Language)
HP designed the PJL such that programmers could provide various job-level settings, including printer language, resolution, etc., as well as request status information from a given device. Hierarchically speaking, the PJL resides above printer languages such as PCL and Postscript.
HP-GL/2 (Hewlett-Packard Graphics Language)
HP supplemented the PCL with a set of graphics commands known as HP-GL/2 for the description of vector graphics in a print job. This language allows a print job to specify printed art as a collection of lines, vectors, polygons, and other geometrical objects. Typically, only large format printers support this language.
RTL (Raster Transfer Language)
This language exists as a subset of the HP-GL/2, which implies its inclusion in the PCL as well. It was created by HP for the purpose of embedding bitmaps (raster images) into HP-GL/2 print jobs. Accordingly, only large format printers commonly support this language.
Epson originally created the ESC/P printer control language to bridge the gap between dot matrix printers and more expensive laser printers. This language added a great deal of page definition capabilities and is the current standard for all Epson printers (i.e. dot matrix, inkjet, large-format, etc.). Both versions of this language (ESC/P and ESC/P2) are raster languages, meaning the document to be printed can only be defined as a bitmap.
LIDIL (Lightweight Imaging Device Interface Language)
This language is commonly used on cheaper HP Deskjets that do not support the PCL printer language. As the name suggests, the language only supports the definition of raster documents, and is very limited overall.

The typical computer user will never encounter the details of these languages, so a "rule of thumb" should adequately cover one's needs. In order to produce the highest quality documents as quickly as possible, a printer's PCL driver (assuming there are multiple options from which to choose) should be selected. If a situation demands the highest possible accuracy in color reproduction (i.e. Pantone color matching), one should choose the Postscript driver (again assuming this is a valid option), unless printing from Microsoft PowerPoint. All known versions of PowerPoint mangle the print job terribly when using a Postscript driver.

Q. What is duplexing?

A. Duplexing is nothing more than a printer's ability to print on both sides of a sheet of paper. Assuming a given printer supports this option (such as a HP LaserJet 9000dn), this will appear as an option in the print setup dialog box, as long as the driver is designed and configured for duplexing. Typically, there will exist a check-box entitled "Print on both sides" or something similar.

Q. What type of printer driver is used in CCIT labs?

A. PCL. Using Postscript drivers create significant delays due to the added complexity and processing requirements. Also, some applications, especially Microsoft PowerPoint, get too involved in the printing process and tend to mangle print jobs when using a Postscript driver.

Q. Why are the suggested plotter drivers labeled as RTL?

A. The large format printers only support the HP-GL/2 subset of the PCL printer language. Labeling these drivers as RTL as opposed to HP-GL/2 may have been chosen due to the simpler character set required by the name.

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