The HP-RTL (Hewlett-Packard's Raster Transfer Language) is a subset of the Printer Command Language (PCL) language. It is used to embed true raster images (bitmaps) into plotter files. The modern plotters (as HP DesignJets) are raster devices, so they need a raster based language. For a backward compatibility they support also HP-GL/2 (formerly HPGL) vector language, so the HP-RTL language is designed for mixing with the HP-GL/2 language.
