A computer printer is an output device and produces hard copy of documents stored in electronic form, usually on paper or transparencies. Printers are primarily used as computer peripherals, and are permanently attached by a printer cable to the computer motherboard. However, network printers, have built-in wireless or Ethernet network interfaces and serve as a printer for any user on the network.
Most printers can directly interface with electronic media such as digital cameras, scanners, memory cards etc.
Some printers come integrated with scanners and/or fax machines. A printer having a scanner can also function as a photocopier.
Types of printers:
Laser Printers: Laser printers are toner based printers and work by adhering toner to a light-sensitive print drum. The toner is then transferred to the printing medium and is fused by heat and pressure. Laser printers are available in both color and monochrome varieties. Laser printers are known for high quality prints and good print speed. They are the more commonly used as printer in offices and are less commonly used as consumer printers due to a high initial cost.
Inkjet Printers: Inkjet printers spray very small precise amounts of ink onto the print media. These drop lets of ink carry a slight electrical charge. The placement of the ink on the page is determined by the charge of a cathode and electrode between which the ink moves. Inkjet printers are the most common consumer printers because of fairly good quality of print and low cost.
Dot Matrix Printers: These printers use a pixels or dots to create images on print media. These printers use printer ribbon similar to a type writer ribbon for printing. Dot matrix printers are commonly used in low-cost, low-quality and/or high volume printing. The impact printing method of these printers allows them to be used to print multi-part documents using carbonless copy paper. At one time, dot matrix printers were one of the more common types of printers for general use. After fall in prices of ink jet printers the use of dot matrix printers for general purpose has declined.
Line Printers: Line printers print an entire line of text at a time. Line printers were the fastest of all impact printers and were used for bulk printing. They were virtually never used with personal computers and have now been replaced by high-speed laser printers.
The unit for measuring speed of a printer is ppm (page per minute). The print quality is measured by dpi (dots per inch). Higher dpi produces better quality images but results in more consumption of ink and slowing down of the printer.