Printers Produce Hardcopy of computer output such as data, text, graphics (drawings or charts). Most computers are designed to receive data in parallel from the computer i.e. 8 bits at a time. Printers have to be connected to the parallel port on the computer, also called LPT1 (Line Pinter 1) 1

Computer Printer Differ in the following aspects: Character Printer: Print one character at a time Line Printer: Print one line at a time Page Printer: Print one page at a time 2

Variety of printing technologies are possible: Dot matrix Daisy Wheel Ink jet Laser Some printers can only handle texts Whereas some printers can handle texts and graphics Variety of standard exists for control codes, which are commands sent from computer to printer to turn on effects such as underlining and emboldening 3

Main Differences between the printers depends on : The quality of output The ability to print graphics The printing speed 4

Character Printer Print one character at a time They are slow printer Capable of printing at the rate of 30 to 300 characters per second (cps) Advantages: Low cost Disadvantages: Slow speed Makes a lot of noise while printing 5

Character Printer Character printers were very popular in the past but these days they are being replaced with inkjet printers. Inkjet printers have the following advatages over character printer. good printing quality, makes less noise fast printing speed produce multicolour printouts. 6

Character printers are of two types: 1. Dot matrix printer 2. Daisy Wheel printer 7

Dot Matrix Printer (Impact matrix printer) Dot Matrix Printers have 9 or 24 pins arranged in the form of matrix To print a character on the paper, the built in microprocessor activates the appropriate pins in the print head to move forward and hit the printer ribbon, which is placed against a paper. As a result the shape of the character appears on the paper. 8

Dot Matrix Printer 9

Dot Matrix printer form the shape of the character by a number of dots and not with the character shape itself. Therefore the print quality is low 10

Daisy wheel Printer The print head of a daisy wheel printer is a circular wheel about 3 inches in diameter with arms/spokes. 11

Daisy wheel Printer The character shapes are embossed at the outer end of the arms. The shape of the printer wheel resembles the petals of a daisy flower, hence it is named daisy wheel printer. 12

Daisy wheel Printer To print a character, the daisy wheel rotates so that the required character is positioned just in front of the printer ribbon. Now the spoke/arm containing the desired character is hit by a hammer and strikes the ribbon leaving an impression on the paper placed behind the ribbon. 13

Movement of all these parts is controlled by microprocessor in the printer. Advantages Print quality is high because exact shape of the character hits the ribbon to leave an impression on paper. 14

Line printer Print one line at a time Faster than character Printer Heavy duty printers and they can print at the rate of 2000 lines per minute. Two types of line printers are: 1. Chain Printer 2. Drum Printer 15

Chain Printer Print characters are contained in a chain which is moved continuously at a rapid rate by two geared pulleys 16

Chain Printer Circuitry within the printer senses when the correct character appears at the desired print position on the page At that point the hammer strikes the page. This action presses the paper against the ribbon and leaves the impression of that character on the paper. When the requirement of the printed line are fulfilled, the printer carriage control moves the page to the next line position. 17

Drum printer The principal of the drum printer is similar to that of the chain printer. All the characters are engraved along the circumference of the drum, and 132 print positions are available. NOTE: Character printer and line printer are called impact printer because they use electro-mechanical mechanism which causes the character shape to strike against the paper and leave an image of the character on the paper. 18

NON-IMPACT PRINTER Laser Printer: Laser printers are page printer, as they print entire page at a time Resembles photocopier in size and appearance. They are very fast, speed being around 8 pages per minute. Silent in operation 19

NON-IMPACT PRINTER Print quality is good to that of daisy printer Resolution of current models is 600 dots per inch (dpi). Some of the latest versions offer 1400 dpi. Laser printers can handle graphics as well as text Print quality is higher than that of inkjet printers Expensive 20

Laser printer Mechanism: Consists of Laser light, roller and toner (ink) A sheet of paper is fed from a tray into the machine and receives an electrostatic charge across its surface. The laser beam traces the computer output (text, graphics) as a pattern of tiny dots on the paper. During this process, it removes the electrostatic charge from the points where the beam strikes the paper. The paper then receives the fine toner across its surface which sticks to the points with no charge. After passing between rollers, the paper come out, heated and dried at the front of the machine. 21

Laser printer 22

LASER PRINTER PROS: Due to the printing process, laser printers can print documents at a much faster rate than inkjet printers. Price by price comparisons tends to favour laser printers over inkjet papers for documents that are not graphically complex. CONS: Warm-up times delay the initial printing start-up time. Toner costs are higher than inkjet ink cartridges. Because the toner has an electrostatic charge, toner will stick to most anything, making toner leaks 23

INKJET PRINTER The inkjet printer works by spraying variable size ink drop PROS: Ideal for printing photographs and other image intensive documents. Inkjets can print onto many types of paper, from cheap office paper to high-end glossy photograph paper. Most inkjet cartridges can be refilled and reused, Which saves money. CONS: Brand new inkjet cartridges tend to be a bit pricey. Inkjet ink is typically water-based, thus making prints highly at risk to water-damage and fading. Ink cartridges need frequent cleaning, which most printers perform automatically. 24