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