The aim of this lecture is to present on Computer Output Device: Dot-matrix Printer. This has a print head that travels across the paper. The head has a set of pins which are pushed out to form the shape of each character. The pins hit an ink ribbon against the paper as the print head moves along. An animation showing how head of a 21 pin dot-matrix printer moves across the paper, firing the pins that strike the ink against the paper. Disadvantages: The printing quality is low – these printers produce low to medium quality black and white printing and can only print low resolution graphics.