9.3 Connecting a Printer
9.3.2 Page Description Language
Page Description Language (PDL) is a code that describes the contents of a document in a language that a printer can understand. These contents include text, graphics, and the overall formatting of the document. PDLs are used by software applications to send WYSIWYG (What You See Is What You Get) "images" to the printer so that the output of the printer mirrors the document laid out on the screen. PDLs also speed up the printing process by sending larger amounts of data to the printer at a time. Lastly, PDLs handle fonts used by the printer. Fonts are sets of formatted text types that can be scaled to various sizes and weights without deteriorating the quality. Fonts are either raster-based (consisting of multiple dots) or vector-based (complicated, outline-oriented fonts). Today there are several popular PDLs:
  • Printer Control Language (PCL) – Developed by Hewlett-Packard to allow software applications to communicate with HP and HP-compatible laser printers, ink-jet printers, and plotters. It is the standard PDL upon which many others are based.
  • PostScript (PS) – Developed by Adobe Systems to allow fonts (text types) to share the same characteristics on screen as well as on paper.
  • Interpress – The Interpress PDL was developed by Xerox to handle its line of high-speed laser printers.

Most current printers are able to understand multiple PDLs (such as PCL and PS) and can use any of the available languages if the proper printer driver is installed.