A page description language (PDL) specifies the arrangement of a printed page through commands from a computer that the printer carries out. Hewlett Packard's Printer Control Language ( PCL ) and Adobe's PostScript are the two most commonly used PDLs.
Modern PDLs describe page elements as geometrical objects, such as lines, arcs, and so on. PDLs define page elements independently of printer technology, so that a page's appearance should be consistent regardless of the specific printer used. The printer itself (rather than the user's computer) processes much of the graphical information. For example, the printer carries out a command to draw a square or a character directly rather than downloading the actual bit s that make up the image of the square or the character from the computer.
Page description languages can be contrasted with content description languages, such as the Extensible Markup Language ( XML ), which describe the content rather than the arrangement of information.