Output Devices

It is an electromechanical device, which accepts data from a computer and translates them into form understand by users.

Following are Output Devices:

1. Printers
2. Plotters

Printers:

Printer is the most important output device, which is used to print data on paper.

Types of Printers: There are many types of printers which are classified on various criteria as shown in fig:

1. Impact Printers: The printers that print the characters by striking against the ribbon and onto the papers are known as Impact Printers.

These Printers are of two types:

1. Character Printers
2. Line Printers

2. Non-Impact Printers: The printers that print the characters without striking against the ribbon and onto the papers are called Non-Impact Printers. These printers print a complete page at a time, therefore, also known as Page Printers.

Page Printers are of two types:

1. Laser Printers
2. Inkjet Printers

Dot Matrix Printers:

Dot matrix has printed in the form of dots. A printer has a head which contains nine pins. The nine pins are arranged one below other. Each pin can be activated independently. All or only the same needles are activated at a time. When needless is not activated, and then the tip of needle stay in the head. When pin work, it comes out of the print head. In nine pin printer, pins are arranged in 5 * 7 matrixes.

Advantage:

1. Dot Matrix Printers prints output as dots, so it can print any shape of the character. This allows the printer to print special character, charts, graphs, etc.
2. Dot Matrix Printers come under the category of impact printers. The printing is done when the hammer pin strikes the inked ribbon. The impressions are printed on paper. By placing multiple copies of carbon, multiple copies of output can be produced.
3. It is suitable for printing of invoices of companies.

Daisy Wheel Printers:

Head is lying on a wheel and Pins corresponding to characters are like petals of Daisy, that's why called Daisy wheel printer.

Advantage:

1. More reliable than DMPs
2. Better Quality

Disadvantage:

1. Slower than DMPs

Drum Printers:

These are line printers, which prints one line at a time. It consists of a drum. The shape of the drum is cylindrical. The drum is solid and has characters embossed on it in the form of vertical bands. The characters are in circular form. Each band consists of some characters. Each line on drum consists of 132 characters. Because there are 96 lines so total characters are (132 * 95) = 12, 672.

Drum contains a number of hammers also.

Chain Printers:

These are called as line printers. These are used to print one line at a line. Basically, chain consists of links. Each link contains one character. Printers can follow any character set style, i.e., 48, 64 or 96 characters. Printer consists of a number of hammers also.

Advantages:

1. Chain or Band if damaged can be changed easily.
2. It allows printing of different form.
3. Different Scripts can be printed using this printer.

Disadvantages:

1. It cannot print charts and graphs.
2. It cannot print characters of any shape.
3. Chain Printers is impact printer, hammer strikes so it is noisy.

Non-Impact Printers:

Inkjet Printers:

These printers use a special link called electrostatic ink. The printer head has a special nozzle. Nozzle drops ink on paper. Head contains up to 64 nozzles. The ink dropped is deflected by the electrostatic plate. The plate is fixed outside the nozzle. The deflected ink settles on paper.

Advantages:

1. These produce high quality of output as compared to the dot matrix.
2. A high-quality output can be produced using 64 nozzles printed.
3. Inkjet can print characters in a variety of shapes.
4. Inkjet can print special characters.
5. The printer can print graphs and charts.

1. Inkjet Printers are slower than dot matrix printers.
2. The cost of inkjet is more than a dot matrix printer.

Laser Printers:

These are non-impact page printers. They use laser lights to produces the dots needed to form the characters to be printed on a page & hence the name laser printers.

The output is generated in the following steps:

Step1: The bits of data sent by processing unit act as triggers to turn the laser beam on & off.

Step2: The output device has a drum which is cleared & is given a positive electric charge. To print a page the modulated laser beam passing from the laser scans back & forth the surface of the drum. The positive electric charge on the drum is stored on just those parts of the drum surface which are exposed to the laser beam create the difference in electric which charges on the exposed drum surface.

Step3: The laser exposed parts of the drum attract an ink powder known as toner.

Step4: The attracted ink powder is transferred to paper.

Step5: The ink particles are permanently fixed to the paper by using either heat or pressure technique.

Step6: The drum rotates back to the cleaner where a rubber blade cleans off the excess ink & prepares the drum to print the next page.