Of all the different types of computer printer, the dot matrix version is by far the most popular for home use. It is cheaper than its daisy wheel and laser counterparts, but has an inferior print quality.
The paper is fed around a platten similar to that of a typewriter, the difference being that the platten can be electrically driven to pull the paper in, instead of the operator manually turning a knob on the side (although this can still be used if required). The platten does not move laterally, instead the print head moves across the paper.
The print head consists of a series of pins, which are arranged in columns. When the signal from the computer reaches the printer, it is decoded and the pins arranged to form the shape of the appropriate character. This is done by a series of electromagnets, each either being on or off. As the pins shoot forward they strike a ribbon, similar to a typewriter ribbon. This marks the paper with several dots, in a configuration to form a character. The appearance is of continuous shapes, but close examination reveals that the dots are not joined together, and the print quality is often poor.
Most dot matrix printers have a near letter quality mode, where
the print head passes over the paper for a second time, printing dots which slightly overlap those printed on the first pass. Another improvement is to have more pins, giving better definition. A good quality dot matrix printer may have 24 pins where a cheaper one could have only 7. However, even a good quality dot matrix printer would normally have a poorer print quality than that of a daisy wheel or laser printer, although unlike the daisy wheel, the dot matrix can print graphics.
