HP-GL, short for Hewlett-Packard Graphics Language and often written as HPGL, is a
printer control language created by
Hewlett-Packard
The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...
(HP). HP-GL was the primary printer control language used by HP
plotter
A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like Polyvinyl chloride, vinyl or leather. In the latter case, they are sometimes k ...
s.
It was introduced with the plotte
HP-9872in 1977 and became a standard for almost all plotters. Hewlett-Packard's
printers also usually support HP-GL/2 in addition to
PCL.
Design
The language is formed from a series of two letter codes (
mnemonic
A mnemonic device ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember.
It makes use of e ...
s), followed by optional parameters. For instance an
arc can be drawn on a page by sending the string:
AA100,100,50;
This means ''Arc Absolute'', and the parameters place the center of the arc at absolute
coordinates
In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine and standardize the Position (geometry), position of the Point (geometry), points or other geometric elements on a manifold such as ...
100,100 on the page, with a starting angle of 50
degrees measured counter-clockwise. A fourth optional parameter (not used here) specifies how far the arc continues, and defaults to 5 degrees.
When first introduced, HP-GL contained the following commands:
Formats:
*
integer formats between -32767 and 32768. No decimal point.
*
decimal format between +/- 127.9999. Optional decimal point.
*
ASCII character
Examples
Typical HP-GL files start with a few setup commands, followed by a long string of graphics commands. The file was in
ASCII
ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...
(
text file
A text file (sometimes spelled textfile; an old alternative name is flat file) is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists stored as data within a computer file system.
In ope ...
)
format, for instance:
The coordinate system was based on the smallest units one of the HP plotters could support, and was set to 25 μm (i.e. 40 units per millimeter, 1016 per inch).
The coordinate space was positive or negative
floating point numbers, specifically ±2
30.
HP-GL/2
The original HP-GL language did 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
Inkjet printing is a type of printer (computing), computer printing that recreates a digital image by propelling droplets of ink onto paper or plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range f ...
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 Hewlett-Packard Graphics Language/2 aka 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 file format was defined that allowed for smaller files and shorter file transfer times, and the minimal resolution was reduced.
AGL
HP-GL is related to AGL (A Graphics Language), an extension of the
BASIC
Basic or BASIC may refer to:
Science and technology
* BASIC, a computer programming language
* Basic (chemistry), having the properties of a base
* Basic access authentication, in HTTP
Entertainment
* Basic (film), ''Basic'' (film), a 2003 film
...
programming language. AGL was implemented on Hewlett-Packard
minicomputers to simplify controlling a plotter. AGL commands describe the desired graphics plotting function, which the computer relays as several HP-GL instructions to the plotter.
See also
*
DMPL, another plotter language by Houston Instruments
*
Gerber format is another plot-description format
*
Logo
A logo (abbreviation of logotype; ) is a graphic mark, emblem, or symbol used to aid and promote public identification and recognition. It may be of an abstract or figurative design or include the text of the name that it represents, as in ...
, a computer language with drawing commands similar to HP-GL
References
Further reading
*
External links
*
*
* (NB. A Python-based HP-GL plotter control library for using vintage pen plotters with contemporary operating systems.)
{{Authority control
HP software
Printing technology
Vector graphics
Page description languages