Re: canibalising old printers

> Date: Tue, 03 Jul 2001 12:55:48 -0000
> From: cadcamcenter@...
>Subject: canibalising old printers

>I understand that most printers are controlled using HPGL rather than
>G-code.

Printers are controlled by a rasterizing process that prints dots. The HP control language is called PCL (Printer Control Language). This is actually a hybrid raster, font, vector based shorthand language and the printer turns it into dots.

HPGL on the other hand is Hewlett Packard Graphics Language and is used to control Plotters. This is a vector based protocall that predates laser printers. It was developed to drive single pens on plotters. The plotter responds to commands like circle, line, pen up, pen color.

Drivers for both pcl and HPGL are included with Windows systems. Printing to file with any of these drivers from Vector-CAD, will give you an example of the language syntax.

Another similar format more common in the Macintosh world is Adobe PostScript. This is a functionally similar format that will drive postscript printers. It has more bells and whistles to control graphics and color for commercial color printing applications.


Note: Technically a vector has only magnitude, direction and sense, but in the common computer vernacular today, vector based means that the format for describing the picture consists of geometric "vectors" indicating JUST the visible portion. (As opposed to raster based that define the status of each point in a picture, print out, display, tool path, etc.) Some of the more common vector entities with the computer based definition are lines, circles or arcs, and points.

Best Regards, Fred Smith- IMService
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