William A. Leonard

Computer hardware hardly ever wears out because it becomes obsolete too quickly. Such is the case with a 6-pen plotter I was given. There was no software for it because it predated Windows and therefore didn't need drivers. Being so old, there is no interest on the part of the manufacturer to develop software for it so I had to write my own control software.

To Windows, a plotter is just another printer. There are plenty of drivers for modern plotters but newer plotters have their own instruction vocabulary that my old plotter doesn't understand.
My approach was to pretend I had a newer plotter and told Windows to print using that plotter but to print to a file. My program reads the file and reduces the instructions to the vocabulary of the 7372 plotter.

A second problem is that so much artwork is represented in the computer in bitmap form (rows of colored dots rather than the start and end points of straight lines). Even artwork such as a map from MapQuest.com where roads appear as lines is really row upon row of colored dots. Unless a program, like AutoCad®, specifically prints "line art" printing such a map on a plotter would result in the pen moving along a horizontal row changing colors along the way; then, moving down to draw the next row and so on. This works perfectly for an ordinary printer where the paper moves one way but is terribly inefficient for a plotter. It should be moving the pen along the paths of the roads.

My program processes the reduced instruction set, detecting the lines and edges in the image and reorganizes the instructions to cause the pen to trace the lines and edges. The panel shown below indicates the status of the plotter and any errors that occur.