PRINTER

Printer is a machine that out puts on paper letters ,numbers or graphs that humans can read. The size, speed ,cost,operation of the devices classified as printers vary widely.

A printer is a computer peripheral device that produces a hard copy (permanent human-readable text and/or graphics, usually on paper) from data stored in a computer connected to it. The world's first computer printer was a 19th-century mechanically driven apparatus invented by Charles Babbage for his Difference Engine.

Monochrome, color and photo printers

• A monochrome printer can only produce an image consisting of one color, usually black. A monochrome printer may also be able to produce graduations of tone of that color, such as a grey-scale.
• A color printer can produce images of multiple colors.
• A photo printer is a color printer that can produce images that mimic the color range (gamut) and resolution of photographic methods of printing.

Laser printers refer to the method used to adhere toner to the media. The advent of cost-effective, precision lasers has made them the dominant toner-based monochrome printer type for home and office applications. Another toner based printer is the LED printer which uses an array of LEDs instead of a laser to cause toner adhesion.

Impact printers rely on a forcible impact to transfer ink to the media, similar to typewriters, that are typically limited to reproducing text. A daisy wheel printer is a specific type of impact printer where the type is moulded around the edge of a wheel. A golf ball typewriter is similar to the daisy wheel type but has the characters distributed over the face of the globe shape.

Dot matrix printers work using a ribbon similar to that found in typewriters.Instead of having individual keys that strike the ribbon,the printer uses a series of needles that are fired from a head, through the ribbon forcing ink onto the page.

An inkjet printer is any printer that places extremely small droplets of ink onto paper to create an image. If you ever look at a piece of paper that has come out of an inkjet printer, you know that:

The dots are extremely small (usually between 50 and 60 microns in diameter), so small that they are tinier than the diameter of a human hair (70 microns)! The dots are positioned very precisely, with resolutions of up to 1440x720 dots per inch (dpi). The dots can have different colors combined together to create photo-quality images.

Line printers, as the name implies, print an entire line of text at a time. Two principle designs existed. In drum printers, a drum carries the entire character set of the printer repeated in each column that is to be printed. In chain printers (also known as train printers), the character set is arranged multiple times around a chain that travels horizontally past the print line. In either 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.

These printers were the fastest of all impact printers and were used for bulk printing in large computer centres. They were virtually never used with personal computers and have now been partly replaced by high-speed laser printers.

The speed of early printers was measured in units of characters per second. More modern printers are measured in pages per minute. These measures are used primarily as a marketing tool, and are not well standardised. Usually pages per minute refers to sparse monochrome office documents, rather than dense pictures which usually print much more slowly

Printer interfaces

Most printers are attached to stand-alone computers via the standard parallel printer port.Afew devices are still connected using serial ports which provide much slower service.Network printers are often connected directly to network server using parallel port,but more elegant solution is place them on the network using Ethernet or standard twisted-pair network connections

Printer driver

a printer driver is a piece of software that converts the data to be printed to the form specific to a printer. The purpose of printer drivers is to allow applications to do printing without being aware of the technical details of each printer model.

On UNIX systems, printer drivers are typically implemented as filters.On Microsoft Windows and Macintosh systems, printer drivers make a part of GDI. Programs then use the same standard APIs to draw text and pictures both on screen and on paper. Printers which use GDI natively are commonly referred to as Winprinters and considered problematic for other operating systems.

Printer drivers should not be confused with print spoolers, that queue print jobs and send them to printer one after the other. On UNIX systems, printer drivers are usually named front end and printer spoolers back end of the printing system.Backends are also used to determinate the available devices. On startup each backend is asked for a list of devices it supports, and any information that is available.

Some manufacturers of printers

• dell
• epson
• hp
• lexmark
• samsung
• and more ...