A printer (or a printing device or a computer printer) is a peripheral device that is able to print or produce what is being shown on-screen onto paper or transparencies. Thus, it is an output device. The output so produced is called a hard copy (since the copy on the computer is called a soft copy). Printers are usually attached to a computer. Printers may also be shared by all computers on a network through the use of various in-built network interfaces such as Ethernet. Printers nowadays can also print directly from pen drives, memory sticks, digital cameras, scanners etc., without requiring a computer. Printers are now sold as combined with other devices (scanners etc.) and are collectively called Multi-functional Devices or MFDs.
As contrary to a printing press which is fast and is meant for high volume print jobs, a printer is slow and cannot print on a large scale. The title of being the first printer is given to the 19th-century mechanical device invented by Charles Babbage (The Father of Computers) for his Difference Engine.
The printers are classified on the basis of the technology that they use to print on a medium. There have been many technologies that have been in use and are now obsolete or serve a special function only. All of the printing technologies (or printer types) are discussed below:
- Impact Printers
Impact printers do not find any use today. Impact printers transfer ink as it is to be printed onto the medium by a stong impact onto the medium. Thus, they come in contact with the medium (usually, paper). This is the same as that in a typewriter. Impact printers are further divided as follows:
- Letter Quality Printers
They are closer to a typewriter. They have am array of hammers each having a single character engraved. Between the medium and the hammers, there is an ink ribbon. When the hammer comes down to strike the medium, the letter engraved gets imprinted onto the medium due to the ribbon. Daisy-wheel printers are letter quality printers. The problem with these pritners was that they could not print graphics at all. However, they produced crisp-quality letters. They are obsolete now.
- Dot-Matrix Printers
Dor matrix printers use a matrix of dots to form a larger image. They were also able to print graphics which was not posible in other impact printers. They were once the most famous type of printers. However, as with all impact printers, they suffered from the problem that they were very slow. Often used as receipt printers till a long time, they are replaced by other types of pritners.
- Line Printers
Line printers are so called due to the fact they printed an entire line of text at a time. Drum printers and Chain or train printers were the two basic types of line printers. Line printers used a very precise timing while ‘hammering’ the medium to print the whole line at once. In all the types of impact printers available, line printers were the fastest. They were hence used in areas where a large amount of printing was required to be done. Interestingly, they were never used alongwith personal computers.
- Thermal Printers
Thermal printers are rarely used and serve only some special purpose. They use special heat-sensitive paper and print on them by using heated regions selectively.
- Toner-Based Printers
Toner based printers adhere a ‘toner’ to the medium. A common type of toner printer is a laser printer. They are fast and very economical and also produce high quality printouts. They are in widespread use today. However, they are a bit costly when compared to others and hence are not common in homes.
- Inkjet Printers
One of most widely used general-printers; inkjet printers use a jet of ink which contains tiny droplets of ink onto the medium. This jet is sprayed in small amounts by a printing head that moves horizontally inside the printer as the paper passes below it. Inkjet pritners are slow as compared to laser printers but are inexpensive and hence are used commercially as well as at home. They use two ink cartridges – one for black ink and the other for the color inks. Almost all of them feature both of the cartridges which in turn can be replaced or refilled when exhausted. Inkjet printers spray very small, precise amounts (usually a few picolitres) of ink onto the media. Inkjet printing (and the related bubble-jet technology) are the most common consumer print technology; as high-quality inkjet printers are inexpensive to produce. Virtually all modern inkjet printers are color devices; some, known as photo printers, include extra pigments to better reproduce the color gamut needed for high-quality photographic prints (and are additionally capable of printing on photographic card stock, as opposed to plain office paper).
Inkjet printers consist of nozzles that produce very small ink bubbles that turn into tiny droplets of ink. The dots formed are the size of tiny pixels. Ink-jet printers can print high quality text and graphics. They are also almost silent in operation. Inkjet printers have a much lower initial cost than do laser printers, but have a much higher cost-per-copy, as the ink needs to be frequently replaced. In addition, consumer printer manufacturers have adapted a business model similar to that employed by manufacturers of razors; the printers themselves are frequently sold below cost, and the ink is then sold at a high markup. Various legal and technological means are employed to try and force users to only purchase ink from the manufacturer (thus leading to vendor lock-in); however there is a thriving aftermarket for such things as third-party ink cartridges (new or refurbished) and refill kits.
Inkjet printers are also far slower than laser printers. Inkjet printers also have the disadvantage that pages must be allowed to dry before being aggressively handled; premature handling can cause the inks (which are adhered to the page in liquid form) to run.
