Dot matrix printing

Dot matrix printing, sometimes called impact matrix printing, is a computer printing process in which ink is applied to a surface using a relatively low-resolution dot matrix for layout. Dot matrix printers are a type of impact printer that prints using a fixed number of pins or wires and typically use a print head that moves back and forth or in an up-and-down motion on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper. They were also known as serial dot matrix printers. Unlike typewriters or line printers that use a similar print mechanism, a dot matrix printer can print arbitrary patterns and not just specific characters.

The perceived quality of dot matrix printers depends on the vertical and horizontal resolution and the ability of the printer to overlap adjacent dots. 9-pin and 24-pin are common; this specifies the number of pins in a specific vertically aligned space. With 24-pin printers, the horizontal movement can slightly overlap dots, producing visually superior output (near letter-quality or NLQ), usually at the cost of speed.

Dot matrix printing is typically distinguished from non-impact methods, such as inkjet, thermal, or laser printing, which also use a bitmap to represent the printed work. These other technologies can support higher dot resolutions and print more quickly, with less noise. Unlike other technologies, impact printers can print on multi-part forms, allowing multiple copies to be made simultaneously, often on paper of different colors. They can also employ endless printing using continuous paper that is fanfolded and perforated so that pages can be easily torn from each other.

In 1925, Rudolf Hell invented the Hellschreiber, an early facsimile-like dot matrix–based teletypewriter device, patented in 1929.

Between 1952 and 1954 Fritz Karl Preikschat filed five patent applications for his so-called "PKT printer", a dot matrix teletypewriter built between 1954 and 1956 in Germany. Like the earlier Hellschreiber, it still used electromechanical means of coding and decoding, but it used a start-stop method (asynchronous transmission) rather than synchronous transmission for communication. In 1956, while he was employed at Telefonbau und Normalzeit GmbH (TuN, later called Tenovis), the device was offered to the Deutsche Bundespost (German Post Office), which did not show interest. When Preikschat emigrated to the US in 1957 he sold the rights to utilize the applications in any country (except the USA) to TuN. The prototype was also shown to General Mills in 1957. An improved transistorized design became the basis for a portable dot matrix facsimile machine, which was prototyped and evaluated for military use by Boeing around 1966–1967.

In 1968, the Japanese manufacturer OKI introduced its first serial impact dot matrix printer (SIDM), the OKI Wiredot. The printer supported a character generator for 128 characters with a print matrix of 7 × 5. It was aimed at governmental, financial, scientific and educational markets. For this achievement, OKI received an award from the Information Processing Society of Japan (IPSJ) in 2013.

In 1970 Digital Equipment Corporation (DEC) introduced an impact dot matrix printer, the LA30, as did Centronics (then of Hudson, New Hampshire): the Centronics 101. The search for a reliable printer mechanism led it to develop a relationship with Brother Industries, Ltd of Japan, and the sale of Centronics-badged Brother printer mechanisms equipped with a Centronics print head and Centronics electronics. Unlike Digital, Centronics concentrated on the low-end line printer marketplace with their distinctive units. In the process, they designed the parallel electrical interface that was to become standard on most printers until it began to be replaced by the Universal Serial Bus (USB) in the late 1990s.

DEC was a major vendor, albeit with a focus on use with their PDP minicomputer line. Their LA30 30 character/second (CPS) dot matrix printer, the first of many, was introduced in 1970. In the mid-1980s, dot-matrix printers were dropping in price, and began to outsell daisywheel printers, due to their higher speed and versatility. The Apple ImageWriter was a popular consumer dot matrix printer in the 1980s until the mid-1990s.