Plotter

We may know about Plotter but you may not know that there are two types of Plotters. 

A plotter is a computerized machine which is much like a printer. The printer works using a pen, pencil, marker, or another writing tool to draw multiple, continuous lines onto paper. It  interprets commands from a computer to the printer for it to be printed. 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. They are most frequently used for computer-aided engineering . 

This program instructs the plotter, in order, to take the first pen (SP1 = Select Pen 1), to go to coordinates X=500, Y=500 on the paper sheet (PA = Plot Absolute), to lower the pen against the paper (PD = Pen Down), to move 1000 units in the Y direction (thus drawing a vertical line - PR = Plot Relative), to lift the pen (PU = Pen Up) and finally to put it back in its stall.