 Plotter

A plotter is a computer-controlled drawing device that produces physical marks by moving a pen or another marking tool relative to a surface. Geometric commands become motions and pen-up or pen-down actions. In a digital stepping plotter, available moves impose a coordinate mesh, so a mathematical line must be approximated by legal steps.

Jack Elton Bresenham's 1965 paper describes a plotter with eight possible neighbor moves, typically on a mesh spaced one hundredth of an inch apart.^[ref] For a segment from $(0,0)$ to $(5,2)$, the controller must distribute two upward increments among five rightward increments. Bresenham's line algorithm updates an integer decision value to choose successive moves. This connects computational geometry to an apparatus whose resolution and permitted motions determine the drawing.