Printer:

• Printer is a peripheral that allows you to make a print out (on paper) of computer data.

• Some printers print only the textual information whereas other printers print graphics also.

• The quality of the printer is determined by its resolution i.e. the clarity of print it can produce.

$\underline{Characteristics \ of \ Printer}:$

• Printer speed: Expressed in pages per minute (ppm), print speed represents the printers ability print a large numbers of pages per minute. Speed varies for color printer.

• Resolution: Expressed in dots per inch (dpi), resolution means the sharpness of printed text. Resolution varies for color print out.

• Warm-up time: The waiting time necessary before the first print-out. A printer cannot print when it is “cold”. A certain temperature must be reached for the printer run optimally.

• Onboard memory: The quantity of memory that allows the printer to store print jobs. The higher the amount of memory, the longer the printer queue can be.

• Paper format: Depending on their size, printers are able to print different sized documents. Generally A4 or A3 size . • Paper feed : The method of loading paper into the printer, characterizing the way in which blank paper is stored.

• The main paper feed modes are:

• The feed tray, which uses an internal paper feed source. Its capacity is equal to the maximum number of sheets of paper that the tray can fit.

• The sheet feeder is a manual feed method that allows you to insert sheets of paper in small quantities (of about 100). The sheet feeder in the back of the printer is either horizontal or vertical.

• Cartridges : cartridges are rarely standard and depend highly on the printer brand and model. Some manufacturers favors multicolored cartridges whereas others offer separate ink cartridges

• It is interesting to examine the printing cost per sheet. The size of the ink drop is especially important. The smaller the drop of ink, the lower the printing cost will be and the better the image quality will be. Some printers produce drops that are 1 or 2 picolitres.

• A picolitre is a trillionth (one millionth of a millionth, or 10 to the -12th power) of a liter, which can be represented numerically as 0.000000000001/liter.

$\underline{Types \ of \ Printer}$:

• There are two types of printers:

• Impact Printers

• Non-impact Printers

• $\underline{Impact \ printers}$: Impact printers print the characters by striking them on the ribbon which is then pressed on the paper. Impact printers are classified into line printers and character printers.

• Line printers print single line at a time and the printing speed varies from 300-3000 lines per minute.

• Character printers print a single character at a time and their printing speed varies from 30-600 characters per second.

• Examples of impact printers:

• $\underline{Dot-matrix \ printers:}$

These printers are examples of impact printers. They print one character at a time and their speed is measured in characters per second.

• $\underline{Dot \ matrix \ printer}$:

• Dots are formed by tiny pins in the print head that strike an inked ribbon against the paper.

• The print head moves leaving a pattern of dots which form letters and images.

• These printers are slow and noisy and are not usually used for personal computers anymore.

• However, since the printing cost is less and several carbon-copies can be printed at the same time, they are used to print airline tickets and shop receipts (shown in fig. above)

$\underline{Daisy \ wheel \ printers}$:

• These printers are able to print letter-quality documents. These documents have the same quality as that produced by a typewriter However, they cannot print graphics. They are slow and expensive than dot matrix printers.

• In these printers, the print head is like a daisy flower and is made up of metallic or plastic wheels. A raised character is placed on the top of the arms of the wheel. For printing any character, the print wheel is rotated until the desired character is under the print hammer. The arm is then struck from behind by the print hammer against the ink ribbon and paper, creating the character.

• Drum printers:

• These printers are much faster than the dot matrix and daisy wheel printers as they print a line in a single operation. • Thus, drum printers are quiet loud, very expensive and produce low quality print. • In these printers, a complete character set is embossed around the circumference of a drum at every print position. For instance, for 110-column printer there are 110 character sets wrapped around the circumference of the drum. • Thus, the drum revolves continuously and when the character is to be printed, the hammer strikes the character.

$\underline{Non-impact \ printers}$:

• Non-impact printers print the characters without using ribbons. They provide a higher speed in terms of characters per second.

• Examples of non-impact printers:

$\underline{Inkjet \ printers}$: The most commonly used printer for home computers is the inkjet printer. These printers form the images on paper by spraying tiny droplets of ink from the print head. Several colored ink can be used to produce colorful printouts.

• $\underline{Inkjet \ printers \ hardly \ make \ any \ noise}$. They are relatively cheap to manufacture but the high cost of the ink make them expensive to operate in the long run.

$\underline{Laser \ printers}$:

• These printers produce marks on paper by using a fine dust called toner. A laser makes the toner stick to the paper forming characters or images. The cost of Laser printers is high but they are cheap to use. A single toner cartridge can print 5000-10,000 pages. The printing is done relatively quietly and very fast compared to other printers, a page is printed in a few seconds. For these reasons laser printers are preferred in offices.