A page description language (PDL) is a language used to describe or construct a printed page (or document). The language works at a higher level than a bitmap, and is meant to act as an intermediary level between a document design application and the printer's native format. PDLs files are typically generated by a print driver, or directly by the application itself. The two most widely used PDLs are PCL (Printer Command Language), developed by HP, and PostScript, developed by Adobe Systems. Most PDLs aren't full programming languages. PostScript is the notable exception.