This document provides information about dot matrix printers. It consists of 3-4 sentences describing how dot matrix printers work by punching ink onto paper in patterns of dots to form letters, with each letter made up of its own dot pattern, usually 7 dots vertically. An example is given of the dot pattern for the letter H. Dot matrix printers are used in applications like railways, cash receipts, and paper works where print quality is not the primary concern.