In the dot matrix printer, this impact happens as the print head fires pins (or print wires) at an ink ribbon, which contacts the paper and leaves a mark. The print head, the assembly, which contains the pins, moves left to right across the paper, one line at a time, creating letters out of the circular dots of ink that impact the paper. Many dot matrix printers also print bi-directionally, which increases the speed. Coils of wires form electromagnets that are called solenoids. When they are energized, they cause the pins to strike forward and force the ribbon against the paper to form a mark.

Caution: The print head on a dot matrix printer may become very hot.

The number of "pins" indicates the quality of the print, such as 9-pin, 24-pin, or 48-pin printers. This is the actual number of pins that are located in the print head. The highest quality of print that is produced by the dot matrix printer is referred to as Near Letter Quality (NLQ). The speed at which a dot matrix printer is able to print is measured in characters per second (cps).

The type of paper that is most often used with the dot matrix printer is continuous feed paper, which has perforated strips on the side. The printer uses pin feeders and tractor feeders to feed the paper and to prevent skewing or shifting. Sheet feeders that print one page at a time were added to some of the higher quality printers used in offices. A large roller, called the platen, applies pressure to keep the paper from slipping. If a multiple-copy paper is used, the platen gap can be adjusted to the thickness of the paper.

Once the least expensive printer, today dot matrix printers are rare and somewhat expensive to purchase because they serve a small market that requires multiple-copy stationary.