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A visual display or board on which a dependent variable is graphed by an automatically controlled pen or pencil as a function of one or more variables.


A device that uses one or more pens that can be raised, lowered and moved over the printing media to draw graphics or text.

The heart of the plotter is the printer head assembly, consisting of a horizontal bar and, attached to it, the head assembly holding the pen in use. The pen can be positioned horizontally by moving the pen assembly along the bar. Vertical positioning is achieved by either moving the bar (stationary page plotter) or the paper (rolling page plotter). Combinations of horizontal and vertical movement are used to draw arbitrary lines and curves in a single action, in contrast to printers which usually scan horizontally across the page.

Colour plots can be made by using more than one pen. Older plotters required a separate pen for each colour and the pens had to be changed by hand. Modern colour plotters usually use only four pens (cyan, magenta, yellow, and black, see CMYK) and need no human intervention to change them.

Monochromatic plotters have been largely phased out by laser printers except when large paper size is needed, e.g. in CAD.


A graphics printer that draws images with ink pens. It actually draws point-to-point lines directly from vector graphics files. The plotter was the first computer output device that could print graphics as well as accommodate full-size engineering and architectural drawings. Using different colored pens, it was also able to print in color long before inkjet printers became an alternative.

Pen plotters are still the most affordable printing device for CAD use and offer resolution unlike any other printer. The lines are not made up of dots. They are actually drawn, providing infinite resolution. See drum plotter, flatbed plotter, electrostatic plotter and inkjet printer.

Drum and Flatbed Plotters
Both types of plotters actually "draw" the images. The drum plotter (left) wraps the paper around a drum with pin feeds. It moves the paper back and forth for one direction of the plot. The pens move across the paper, creating the other axis. The bed of the flatbed unit (right) determines the maximum size of the total drawing.

Drawing Pens
Pen plotters use drawing pens that provide infinite resolution, because the lines are actually drawn. All other printing devices print dots.