9-pin dot matrix
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A Dot matrix printer in which the print head has nine separate pins arranged vertically. This is a sufficient number to produce each alphanumeric character with only one pass of the print head on each line, which means the page can be printed fairly quickly, albeit with a rather unattractive "spotty" appearance. This type of output is often known as "draft mode".
Many 9-pin printers have built in support for "NLQ" ("Near Letter Quality") output, in which the print head makes multiple passes to produce each printed line, each time with a slight vertical and/or horizontal offset. This has the effect of producing dots between the existing dots, and increasing the effective resolution and the appearance. However, this is at a substantial cost in terms of the time taken to produce each page.
Even printers which lack this NLQ feature often have a "graphics mode" where the computer can directly control the motion of the printhead, roller, and firing of the pins. Operating systems like Windows 3.0 supported this feature, and allowed NLQ text and relatively high quality graphics from a humble printer. Typical resolutions are 240x144 dpi.