HP-GL (Hewlett-Packard Graphics Language) is a vector graphics language, a type of object-oriented language that represents images through the use of geometrical formulas. Vector graphics are more efficient than the alternative, raster graphics: they require less memory space for storage and use input/output (I/O) resources more effectively so that images print more quickly. For example, to print a line using HP-GL, the printer defines the end points and then merely connects the two; using raster graphics, the printer must define not only the end points, but each point between them. HP-GL enables a printer to function as a plotter.
HP-GL is a subset of Hewlett-Packard's Printer Control Language (PCL), a page description language (PDL) that is used to define the layout and content of a printed page.