1. A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens.
2. Unlike a regular printer, the plotter can draw continuous point-to-point lines directly from vector graphics files or commands. There are a number of different types of plotters: a drum plotter draws on paper wrapped around a drum which turns to produce one direction of the plot, while the pens move to provide the other direction; a flatbed plotter draws on paper placed on a flat surface; and an electrostatic plotter draws on negatively charged paper with positively charged toner.
3. Plotters were the first type of printer that could print with color and render graphics and full-size engineering drawings. As a rule, plotters are much more expensive than printers.
4. They are most frequently used for CAE (computer-aided engineering) applications, such as CAD (computer-aided design) and CAM (computer-aided manufacturing). Hewlett-Packard is the leading vendor of plotters worldwide.
5. An application need not know the names of all the modules or entry points that may be called. For example, a charting program may be written to work with a variety of plotters, each of which is driven by a different driver package. The application can learn the name of the plotter that is currently installed on the system from another process or by looking it up in a configuration file. This allows the user of the application to install a new plotter that did not exist at the time the application was written.
6. It is a device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolor plotters use different-colored pens to draw different colors.
7. They are used in engineering applications where precision is mandatory.

Working:

1. A plotter works closely with a computer's imaging software to produce a final picture or object. The first step in using a plotter is to enter the appropriate coordinates for where you want the image to appear on the paper. Modern software allows the user to accomplish this goal very easily by drawing lines and images with the imaging software.
2. Once the schematics for the image are complete, the computer downloads the coordinates to the plotter, which interprets the code and calculates the most efficient path for the pen and paper. Newer plotters use one of two programming languages: Hewlett-Packard's HPGL2 or Houston Instruments' DMPL.
3. Early plotters contained two separate pens, one that moved vertically and one that moved horizontally. These plotters were limited in terms of the complexity of the images they could produce as well as the speed at which they could operate. Modern plotters use a sliding roller, which moves the paper against a stationary pen.
4. A plotter pen is usually a hollow fiber rod with a sharpened end. The ink supply runs through the center of the rod and dispenses through the sharpened tip. The paper moves horizontally and vertically against the pen until the drawing is complete.