Specifications

Although PCL is wholly owned and developed by Hewlett-Packard, this company’s long-term domi-
nance in the printer market has made it a de facto standard. Many other companies manufacture
printers that use PCL and often advertise these printers as being compatible with a specific Hewlett-
Packard model.
Note
Most HP inkjet printers use stripped-down versions of PCL; see the particular printer’s documentation for information on
which PCL features it supports.
PostScript
PostScript is a page description language developed by Adobe that first introduced in the Apple
LaserWriter printer in 1985. PostScript possessed capabilities at its inception, such as scalable type and
vector graphics support, that were only added to PCL years later. For this reason, PostScript quickly
became and still remains the industry standard for desktop publishing and graphics work. Adobe
licenses the PostScript language to many printer manufacturers, including those that make the high-
resolution image setters used by service bureaus to produce camera-ready output for the offset print-
ing processes used by newspaper, magazine, and book printers.
PostScript does not use escape code sequences like PCL does; it is more like a standard programming
language. PostScript is called an object-oriented language because the printer sends images to the
printer as geometrical objects rather than bitmaps. This means that to produce type using a particular
font, the printer driver specifies a font outline and a specific size. The font outline is a template for
the creation of the font’s characters at any size. The printer actually generates the images of the char-
acters from the outline, rather than calling on a stored bitmap of each character at each size. This
type of image that is generated specifically for use on a particular page is called a vector graphic—as
opposed to a bitmap graphic, which arrives at the printer as a fully formed dot pattern. PCL did not
have the capability to print scalable type until version 5 was introduced in 1990.
When it comes to printing fonts, outlines simplify the process by enabling printers to be equipped
with more internal fonts that can be printed at any size. Bitmapped fonts, on the other hand, usually
must be downloaded to the printer from the PC. When graphic images are involved, the difference
between a vector-based object and a bitmap often can be seen in the printed output. Because a vector
image is actually generated inside the printer, its quality is based on the printer’s capabilities. Printing
a vector image on a 600dpi printer produces a much better quality product than printing the same
image on a 300dpi printer. A bitmap image, on the other hand, generates the same output on either
printer.
At first, modifications to the PostScript language were based on the evolving capabilities of the Apple
laser printers that were its primary outlet. These minor modifications eventually became numerous
enough for Adobe to release a new baseline version of the language called PostScript Level 2 in 1992.
The evolution continued, and PostScript 3, the most recent version of PostScript, was introduced in
1997. These updates improved the speed and performance of PostScript printers and accommodated
their physical changes, such as increased amounts of memory and added paper trays, but they did not
introduce revolutionary new features the way the PCL updates did. PostScript had its most powerful
features from the very beginning, and the succeeding revisions of the language remain backward-
compatible.
Note
PostScript provides the basis for the PDF (Portable Document Format) files you can create with Adobe Acrobat, and
PostScript level 3 can print PDF files directly, without the need for an application to process the print job.