Plotters are computer output devices similar to printers, but instead of rendering text and graphics as dots, they use vector instructions to draw lines on a surface. Commonly, plotters use a pen to draw images, but they also may use ink jets, heated elements or even knives.
The most common pen plotters use one or more stepper motors attached to a pulley system that moves a vertical pen over a surface, usually mounted with paper. Sometimes the motors move the surface and the pen is kept stationary. The motors are given commands contained in vector files that determine when the pen is up or down, as well as how long and in what direction lines should be drawn. Because the plotter draws entire lines at a time, complex images with many lines can take much longer to render than with other printing devices.
Since they draw vector lines instead of individual dots, plotters do not have any resolution limits beyond the ability of the stepper motor used to control the pen. Therefore, they can produce resoundingly clean and accurate images. Their use has become more limited as wide format printers have become available that are more efficient, faster and able to produce more photographic output than plotters.