HP Graphics Language (HP GL), (Printer Languages)

HPGL, sometimes hyphenated as HP-GL, is the primary printer control language used by Hewlett-Packard plotters. The name is an initialism for Hewlett-Packard Graphics Language. It later became a standard for almost all plotters. Hewlett-Packard’s printers also usually support HPGL in addition to PCL.
The Hewlett Packard Graphics Language (HP GL) is widely used by pen plotters used to produce engineering drawings. HP GL has been widely emulated by other plotter manufacturers, and is the de facto standard language for pen plotters. A pen plotter is a slow device, a complex drawing can easily take have an hour to plot, and plotters are often noisy and difficult to set up. For these reasons many laser printers offer an HP GL emulation, normally copying the HP7475A desktop plotter, which can be used for draft prints of drawings.
As most laser printers do not print in color, and cannot print on the very large paper sizes used by plotters, they are normally only used for draft prints, but in a few situations, such as printed circuit board designs, laser printers are used in preference to plotters. HP GL version 2 has been incorporated into the PCL 5 language to provide PCL with vector graphics capabilities. HPGL uses two-letter mnemonics as instructions for drawing lines, circles, text, and simple symbols. HPGL has evolved over the years as HP added features to its line of pen, electrostatic, inkjet, and laser plotters and printers.
There is one primary drawback to HPGL: it is bulkier than other plotting languages, which means it takes longer to transmit an HPGL plot file. To overcome the limitation, Hewlett-Packard in 1988 introduced HPGL/2, which featured “polyline encoding,” a form of data compression that reduces the plot file size and, hence, transmission time by two-thirds.
The original HP/GL-Language does not support definition of line width, as this parameter was determined by the pens loaded into the plotter. With the advent of the first inkjet plotters, line width for the “pens” specified within the HP/GL-files had to be set at the printer so it would know what line width to print for each pen, a cumbersome and error-prone process. With HP/GL-2, definition of line width was introduced into the language and allowed for elimination of this step. Also, among other improvements a binary format was defined that allowed for smaller files and shorter file transfer times, and the minimal resolution was reduced.