Each dot is produced by a tiny metal rod or "pin", which uses the power of a tiny electromagnet or solenoid to drive it forward. Generally the print head prints one line of text at a time. Most dot matrix printers have a single vertical line of dot-making equipment on their print heads; others have a few interleaved rows in order to improve dot density.
Certain models produce double-wide or bold characters by printing each vertical slice of a character twice. It produces higher resolutions by moving the print head more slowly. It produces graphics by printing dots, one horizontal character-high stripe at a time. Though most print in black and white, a few produce colour by making extra passes, shifting a multi-color striped ink ribbon between passes.
They are inexpensive, and until the 1990s the most common form of printer used with PCss. The groundbreaking model that drove their initial popularity was the Epson MX-80. However, they were notorious in homes and offices for their loud buzzing sound when printing (finally softened in some later models), generally slow printing, and for unattractive, spotty printouts unless the user paid extra for a fancy-printing program such as Bradford or, later, Windows 3.1.
Dot matrix impact printers remain in use in devices such as cash registers, ATM printouts and in industry where a carbon copy is required.
Nearly all inkjet, bubblejet, and laser printers use a dot matrix to describe each character or graphic. In common parlance these are seldom called dot-matrix printers, to avoid confusion with dot matrix impact printers.