In computing, a printer is a peripheral which makes a persistent human readable representation of

graphics or text on paper or similar physical media.[1] The two most common printer mechanisms are

black and white laser printers used for common documents, and colorinkjet printers which can

produce high quality photograph quality output.

The world's first computer printer was a 19th-century mechanically driven apparatus invented

by Charles Babbage for his difference engine.[2] This system used a series of metal rods with

characters printed on them and stuck a roll of paper against the rods to print the characters. The first

commercial printers generally used mechanisms from electric typewriters and Teletype machines,

which operated in a similar fashion. The demand for higher speed led to the development of new

systems specifically for computer use. Among the systems widely used through the 1980s

were daisy wheel systems similar to typewriters, line printers that produced similar output but at

much higher speed, and dot matrix systems that could mix text and graphics but produced relatively

low-quality output. The plotter was used for those requiring high quality line art like blueprints.

The introduction of the low-cost laser printer in 1984 with the first HP LaserJet, and the addition

of PostScript in next year's Apple LaserWriter, set off a revolution in printing known as desktop

publishing. Laser printers using PostScript mixed text and graphics, like dot-matrix printers, but at

quality levels formerly available only from commercial typesetting systems. By 1990, most simple

printing tasks like fliers and brochures were now created on personal computers and then laser

printed; expensive offset printing systems were being dumped as scrap. The HP Deskjet of 1988

offered the same advantages as laser printer in terms of flexibility, but produced somewhat lower

quality output (depending on the paper) from much less expensive mechanisms. Inkjet systems

rapidly displaced dot matrix and daisy wheel printers from the market. By the 2000s high-quality

printers of this sort had fallen under the $100 price point and became commonplace.

The rapid update of internet email through the 1990s and into the 2000s has largely displaced the

need for printing as a means of moving documents, and a wide variety of reliable storage systems

means that a "physical backup" is of little benefit today. Even the desire for printed output for "offline

reading" while on mass transit or aircraft has been displaced by e-book readers and tablet

computers. Today, traditional printers are being used more for special purposes, like printing

photographs or artwork, and are no longer a must-have peripheral.

Starting around 2010, 3D printing became an area of intense interest, allowing the creation of

physical objects with the same sort of effort as an early laser printer required to produce a brochure.

These devices are in their earliest stages of development and have not yet become commonplace.

Types of printers[edit]

Personal printers are primarily designed to support individual users, and may be connected to only a

single computer. These printers are designed for low-volume, short-turnaround print jobs, requiring

minimal setup time to produce a hard copy of a given document. However, they are generally slow

devices ranging from 6 to around 25 pages per minute (ppm), and the cost per page is relatively

high. However, this is offset by the on-demand convenience. Some printers can print documents

stored on memory cards or from digital cameras and scanners.

Networked or shared printers are "designed for high-volume, high-speed printing." They are usually

shared by many users on a network and can print at speeds of 45 to around 100 ppm.[3] The Xerox

9700 could achieve 120 ppm.

A virtual printer is a piece of computer software whose user interface and API resembles that of a

printer driver, but which is not connected with a physical computer printer.

A 3D printer is a device for making a three-dimensional object from a 3D model or other electronic

data source through additive processes in which successive layers of material ( including plastics,

metals, food, cement, wood, and other materials) are laid down under computer control. It is called a

printer by analogy with an inkjet printer which produces a two-dimensional document by a similar

process of depositing a layer of ink on paper.

Technology[edit]

The choice of print technology has a great effect on the cost of the printer and cost of operation,

speed, quality and permanence of documents, and noise. Some printer technologies don't work with

certain types of physical media, such as carbon paper or transparencies.

A second aspect of printer technology that is often forgotten is resistance to alteration: liquid ink,

such as from an inkjet head or fabric ribbon, becomes absorbed by the paper fibers, so documents

printed with liquid ink are more difficult to alter than documents printed with toner or solid inks, which

do not penetrate below the paper surface.

Cheques can be printed with liquid ink or on special cheque paper with toner anchorage so that

alterations may be detected.[4] The machine-readable lower portion of a cheque must be printed

using MICR toner or ink. Banks and other clearing houses employ automation equipment that relies

on the magnetic flux from these specially printed characters to function properly.

Modern print technology[edit]

The following printing technologies are routinely found in modern printers:

Toner-based printers[edit]

Main article: Laser printer

A laser printer rapidly produces high quality text and graphics. As with digital photocopiers and

multifunction printers (MFPs), laser printers employ a xerographic printing process but differ from

analog photocopiers in that the image is produced by the direct scanning of a laser beam across the

printer's photoreceptor.

Another toner-based printer is the LED printer which uses an array of LEDs instead of a laser to

cause toner adhesion to the print drum.

Liquid inkjet printers[edit]

Liquid ink cartridge from Hewlett-Packard HP 845C inkjet printer

Inkjet printers operate by propelling variably sized droplets of liquid ink onto almost any sized page.

They are the most common type of computer printer used by consumers.

Solid ink printers[edit]

Main article: Solid ink

Solid ink printers, also known as phase-change printers, are a type of thermal transfer printer. They

use solid sticks of CMYK-coloured ink, similar in consistency to candle wax, which are melted and

fed into a piezo crystal operated print-head. The printhead sprays the ink on a rotating, oil coated

drum. The paper then passes over the print drum, at which time the image is immediately

transferred, or transfixed, to the page. Solid ink printers are most commonly used as colour office

printers, and are excellent at printing on transparencies and other non-porous media. Solid ink

printers can produce excellent results. Acquisition and operating costs are similar to laser printers.

Drawbacks of the technology include high energy consumption and long warm-up times from a cold

state. Also, some users complain that the resulting prints are difficult to write on, as the wax tends to

repel inks from pens, and are difficult to feed through automatic document feeders, but these traits

have been significantly reduced in later models. In addition, this type of printer is only available from

one manufacturer, Xerox, manufactured as part of their Xerox Phaser office printer line.

Previously, solid ink printers were manufactured by Tektronix, but Tek sold the printing business to

Xerox in 2001.

Dye-sublimation printers[edit]

Main article: Dye-sublimation printer

A disassembled dye sublimation cartridge.

A dye-sublimation printer (or dye-sub printer) is a printer which employs a printing process that uses

heat to transfer dye to a medium such as a plastic card, paper or canvas. The process is usually to

lay one colour at a time using a ribbon that has colour panels. Dye-sub printers are intended

primarily for high-quality colour applications, including colour photography; and are less well-suited

for text. While once the province of high-end print shops, dye-sublimation printers are now

increasingly used as dedicated consumer photo printers.

Inkless printers[edit]

Receipt printer printing a Twitter timeline

inkless printers work by selectively heating regions of special heat-sensitive paper. Monochrome

thermal printers are used in cash registers, ATMs, gasoline dispensers and some older inexpensive

fax machines. Colours can be achieved with special papers and different temperatures and heating

rates for different colours; these coloured sheets are not required in black-and-white output. One

example is the ZINK technology (Zero INK Technology).[5]

Obsolete and special-purpose printing technologies[edit]

Epson MX-80, a popular model of dot-matrix printer in use for many years

The following technologies are either obsolete, or limited to special applications though most were,

at one time, in widespread use.

Impact printers[edit]

Impact printers rely on a forcible impact to transfer ink to the media. The impact printer uses a print

head that either hits the surface of the ink ribbon, pressing the ink ribbon against the paper (similar

to the action of a typewriter), or, less commonly, hits the back of the paper, pressing the paper

against the ink ribbon (the IBM 1403 for example). All but the dot matrix printer rely on the use

of fully formed characters, letterforms that represent each of the characters that the printer was

capable of printing. In addition, most of these printers were limited to monochrome, or sometimes

two-color, printing in a single typeface at one time, although bolding and underlining of text could be

done by "overstriking", that is, printing two or more impressions either in the same character position

or slightly offset. Impact printers varieties include typewriter-derived printers, teletypewriter-derived

printers, daisywheel printers, dot matrix printers and line printers. Dot matrix printers remain in

common use in businesses where multi-part forms are printed. An overview of impact

printing[6]contains a detailed description of many of the technologies used.

Typewriter-derived printers[edit]

typeball print element from IBM Selectric-type printer

Main articles: Friden Flexowriter  and IBM Selectric typewriter

Several different computer printers were simply computer-controllable versions of existing electric

typewriters. The Friden Flexowriter  andIBM Selectric-based printers were the most-common

examples. The Flexowriter printed with a conventional typebar mechanism while the Selectric used

IBM's well-known "golf ball" printing mechanism. In either case, the letter form then struck a ribbon

which was pressed against the paper, printing one character at a time. The maximum speed of the

Selectric printer (the faster of the two) was 15.5 characters per second.

Teletypewriter-derived printers[edit]

Main article: Teleprinter

The common teleprinter could easily be interfaced to the computer and became very popular except

for those computers manufactured by IBM. Some models used a "typebox" that was positioned, in

the X- and Y-axes, by a mechanism and the selected letter form was struck by a hammer. Others

used a type cylinder in a similar way as the Selectric typewriters used their type ball. In either case,

the letter form then struck a ribbon to print the letterform. Most teleprinters operated at ten

characters per second although a few achieved 15 CPS.

Daisy wheel printers[edit]

"daisy wheel" print element

Main article: Daisy wheel printer

Daisy wheel printers operate in much the same fashion as a typewriter. A hammer strikes a wheel

with petals, the "daisy wheel", each petal containing a letter form at its tip. The letter form strikes a

ribbon of ink, depositing the ink on the page and thus printing a character. By rotating the daisy

wheel, different characters are selected for printing. These printers were also referred to as letter-

quality printersbecause they could produce text which was as clear and crisp as a typewriter. The

fastest letter-quality printers printed at 30 characters per second.

Dot-matrix printers[edit]

Main article: Dot matrix printer

sample output from 9-pin dot matrix printer (one character expanded to show detail)

The term dot matrix printer is used for impact printers that use a matrix of small pins to transfer ink to

the page. The advantage of dot matrix over other impact printers is that they can

producegraphical images in addition to text; however the text is generally of poorer quality than

impact printers that use letterforms (type).

Dot-matrix printers can be broadly divided into two major classes:

Ballistic wire printers

Stored energy printers

Dot matrix printers can either be character-based or line-based (that is, a single horizontal series of

pixels across the page), referring to the configuration of the print head.

In the 1970s & 80s, dot matrix printers were one of the more common types of printers used for

general use, such as for home and small office use. Such printers normally had either 9 or 24 pins

on the print head (early 7 pin printers also existed, which did not print descenders). There was a

period during the early home computer era when a range of printers were manufactured under many

brands such as the Commodore VIC-1525 using the Seikosha Uni-Hammer system. This used a

single solenoid with an oblique striker that would be actuated 7 times for each column of 7 vertical

pixels while the head was moving at a constant speed. The angle of the striker would align the dots

vertically even though the head had moved one dot spacing in the time. The vertical dot position was

controlled by a synchronised longitudinally ribbed platen behind the paper that rotated rapidly with a

rib moving vertically seven dot spacings in the time it took to print one pixel column.[7][8] 24-pin print

heads were able to print at a higher quality and started to offer additional type styles and were

marketed as Near Letter Quality by some vendors. Once the price of inkjet printers dropped to the

point where they were competitive with dot matrix printers, dot matrix printers began to fall out of

favour for general use.

Some dot matrix printers, such as the NEC P6300, can be upgraded to print in colour. This is

achieved through the use of a four-colour ribbon mounted on a mechanism (provided in an upgrade

kit that replaces the standard black ribbon mechanism after installation) that raises and lowers the

ribbons as needed. Colour graphics are generally printed in four passes at standard resolution, thus

slowing down printing considerably. As a result, colour graphics can take up to four times longer to

print than standard monochrome graphics, or up to 8-16 times as long at high resolution mode.

Dot matrix printers are still commonly used in low-cost, low-quality applications such as cash

registers, or in demanding, very high volume applications like invoice printing. Impact printing, unlike

laser printing, allows the pressure of the print head to be applied to a stack of two or more forms to

print multi-part documents such as sales invoices and credit card receipts using continuous

stationery with carbonless copy paper. Dot-matrix printers were being superseded even as receipt

printers after the end of the twentieth century.

Line printers[edit]

Main article: Line printer

IBM 1403 line printer

Line printers, as the name implies, print an entire line of text at a time. Four principal designs

existed.

Drum printers, where a horizontally mounted rotating drum carries the entire character set of the

printer repeated in each printable character position. The IBM 1132 printer is an example of a

drum printer. Drum printers were also found in adding machines and other numeric printers

(POS), the dimensions were compact as only a dozen characters needed to be supported.[9]

Chain or train printers, where the character set is arranged multiple times around a linked chain

or a set of character slugs in a track traveling horizontally past the print line. The IBM 1403 is

perhaps the must popular, and came in both chain and train varieties. The band printer is a later

variant where the characters are embossed on a flexible steel band. The LP27 from Digital

Equipment Corporation is a band printer.

Bar printers, where the character set is attached to a solid bar that moves horizontally along the

print line, such as the IBM 1443.[10]

A fourth design, used mainly on very early printers such as the IBM 402, featured independent

type bars, one for each printable position. Each bar contained the character set to be printed.

The bars moved vertically to position the character to be printed in front of the print hammer. [11]

In each case, to print a line, precisely timed hammers strike against the back of the paper at the

exact moment that the correct character to be printed is passing in front of the paper. The paper

presses forward against a ribbon which then presses against the character form and the impression

of the character form is printed onto the paper.

Comb printers, also called line matrix printers, represent the fifth major design. These printers

were a hybrid of dot matrix printing and line printing. In these printers, a comb of hammers

printed a portion of a row of pixels at one time, such as every eighth pixel. By shifting the comb

back and forth slightly, the entire pixel row could be printed, continuing the example, in just eight

cycles. The paper then advanced and the next pixel row was printed. Because far less motion

was involved than in a conventional dot matrix printer, these printers were very fast compared to

dot matrix printers and were competitive in speed with formed-character line printers while also

being able to print dot matrix graphics. The Printronix P7000 series of line matrix printers are still

manufactured as of 2013.

Line printers were the fastest of all impact printers and were used for bulk printing in large computer

centres. A line printer could print at 1100 lines per minute or faster, frequently printing pages more

rapidly than many current laser printers. On the other hand, the mechanical components of line

printers operated with tight tolerances and required regular preventive maintenance (PM) to produce

top quality print. They were virtually never used with personal computers and have now been

replaced by high-speedlaser printers. The legacy of line printers lives on in many computer operating

systems, which use the abbreviations "lp", "lpr", or "LPT" to refer to printers.

Liquid ink electrostatic printers[edit]

This section needs additional citations for verification. Please

help improve this article by adding citations to reliable sources.

Unsourced material may be challenged and removed. (May 2012)

Liquid ink electrostatic printers use a chemical coated paper, which is charged by the print head

according to the image of the document. The paper is passed near a pool of liquid ink with the

opposite charge. The charged areas of the paper attract the ink and thus form the image. This

process was developed from the process of electrostatic copying.[12] Color reproduction is very

accurate, and because there is no heating the scale distortion is less than ±0.1%. (All laser printers

have an accuracy of ±1%.)

Worldwide, most survey offices used this printer before color inkjet plotters become popular. Liquid

ink electrostatic printers were mostly available in 36 to 54 inches (910 to 1,370 mm) width and also 6

color printing. These were also used to print large billboards. It was first introduced by Versatec,

which was later bought by Xerox. 3M also used to make these printers.[13]

Plotters[edit]

Main article: Plotter

A Calcomp 565 drum plotter.

Pen-based plotters were an alternate printing technology once common in engineering and

architectural firms. Pen-based plotters rely on contact with the paper (but not impact, per se) and

special purpose pens that are mechanically run over the paper to create text and images. Since the

pens output continuous lines, they were able to produce technical drawings of higher resolution than

was achievable with dot-matrix technology.[14] Some plotters used roll-fed paper, and therefore had

minimal restriction on the size of the output in one dimension. These plotters were capable of

producing quite sizable drawings.

Other printers[edit]

A number of other sorts of printers are important for historical reasons, or for special purpose uses:

Digital minilab  (photographic paper)

Electrolytic printers

Spark printer

Barcode printer multiple technologies, including: thermal printing, inkjet printing, and laser

printing barcodes

Billboard / sign paint spray printers

Laser etching (product packaging) industrial printers

Microsphere (special paper)

Attributes[edit]

Printer control languages[edit]

Most printers other than line printers accept control characters or unique character sequences to

control various printer functions. These may range from shifting from lower to upper case or from

black to red ribbon on typewriter printers to switching fonts and changing character sizes and colors

on raster printers. Early printer controls were not standardized, with each manufacturer's equipment

having its own set. The IBM Personal Printer Data Stream (PPDS) became a commonly used

command set for dot-matrix printers.

Today, most printers accept one or more page description languages (PDLs). Laser printers with

greater processing power frequently offer support for variants of Hewlett-Packard's Printer

Command Language (PCL), PostScript or XML Paper Specification. Most inkjet devices support

manufacturer proprietary PDLs such as ESC/P. The diversity in mobile platforms have led to various

standardization efforts around device PDLs such as the Printer Working Group (PWG's) PWG

Raster.

Printing speed[edit]

The speed of early printers was measured in units of characters per minute (cpm) for character

printers, or lines per minute (lpm) for line printers. Modern printers are measured in pages per

minute (ppm). These measures are used primarily as a marketing tool, and are not as well

standardised as toner yields. Usually pages per minute refers to sparse monochrome office

documents, rather than dense pictures which usually print much more slowly, especially colour

images. PPM are most of the time referring to A4 paper in Europe and letter paper in the United

States, resulting in a 5-10% difference.

Sales[edit]

Since 2005, the world's top selling brand of inkjet and laser printers has been HP, which now has

46% of sales in inkjet and 55.5% in laser printers.[15]

Printing mode[edit]

The data received by a printer may be:

A string of characters

A bitmapped image

A vector image

A computer program written in a page description language, such as PCL or PostScript

Some printers can process all four types of data, others not.

Character printers, such as daisy wheel printers, can handle only plain text data or rather simple

point plots.

Pen plotters typically process vector images. Inkjet based plotters can adequately reproduce all

four.[citation needed]

Modern printing technology, such as laser printers and inkjet printers, can adequately reproduce

all four. This is especially true of printers equipped with support for PCL or PostScript, which

includes the vast majority of printers produced today.

Today it is possible to print everything (even plain text) by sending ready bitmapped images to the

printer. This allows better control over formatting, especially among machines from different vendors.

Many printer drivers do not use the text mode at all, even if the printer is capable of it.[citation needed]