OUTPUT UNIT

The results of the data processed by the computer are available in electronic signals. The
output unit converts these signals into a form which could be easily understood by us. The
output is usually given either on the screen by visual display unit/monitor or in a printed form by
printers.

a) Monitor (Visual Display Unit or Screen)

The monitor is made up of cathode-ray tube CRT due to which it also called C.R.T terminal. The screen consists of horizontal and vertical sweep circuits similar to T.V. sets. The screen’s inside is
coated with dots of phosphor called pixel and can be used for games or graphics or displaying the
results of a calculation done by computer. The more the number of pixel or dots in a screen, the better will be the capability of computer to display an information.
This capability is known as resolution. The characters typed with the keyboard are displayed on the screen. We can thus verify whether the programs we enter into computer is corrector not.

Tips for avoiding computer vision syndrome:

Long hours of staring at a computer screen causes dryness and reduces the blinking rate
of the eyes. Burning, itchiness and watering of eyes are the common visible syndromes of
computer vision syndrome. Often headache is a direct consequence of the glare emitted by the
screen.

•  To avoid the syndrome the following measures are to be taken:
•  Make sure that the computer screen is not too close to your face.
•  Position the screen so that it is either at eye level, or slightly lower.
•  Tilt the monitor slightly to eliminate reflection or glare.
•  Make sure that primary light source [such as windows] is not shining into your face or directly on the monitor.
•  Frequently look away from the screen and focus on far away objects.
•  Reduce the contrast and brightness of the screen by adjusting the controls on the monitor.

 b) Printer

Printer is the most commonly used output device. It is used to prepare permanent
documents in human – readable form [hard copy]. The are several types of printers that are
designed for different types of applications.
Printers are of two types-impact and non impact. Impact printers use the familiar
typewriter approach of hammering a typeface against paper and inked ribbon. Non- impact
printers do not hit or impact a ribbon to print. They use thermal, electrostatic, chemical and
inkjet technologies.
Depending on their speed and approach of printing, printers are also classified as
character printers, and page printers.

Types of Printers:

1. Dot Matrix Printer:

In this printer characters to print are made up of a finite number of dots and so, the print head consists of an array of pins. Characters to be printed are made up of a finite number of dots and so, the printer. The character code is decoded by the printer electronics and activates the appropriate pins in the print head. Many dot matrix printers are bi-directional. i.e., they print from left to right as well as from right to left on return. This enhances the speed of printing. The printing speed is around 300 characters per second.

 2. Line Printer:

Unlike a dot matrix printer, line printer prints a complete line at a time. Two types of line printers are
available.

3. Drum Printer

It consists of cylindrical drum. The characters to be printed are embossed on its surface.

4. Chain Printer:

It has a steel band on which the character sets are embossed. Printing speed varies from 150 lines to
2500 lines per minute with 96 to 160 characters on a 15 inch line. Six to eight lines per vertical inch are printed. Usually 64 and 96 character sets are used with English letters.

 5. Inkjet Printer:

It consists of print heard, which has a number of small holes of nozzles. Individual holes are heated very rapidly by an integrated circuit resistor. When the resistor heats up, the ink near it vaporizes and  is ejected through the nozzle and makes a dot on paper placed near the head. A high – resolution inkjet printer has around 50 nozzles within a height of 7mm and can print with a resolution of more than 300 dots per inch. Latest inkjet printers have multimedia heads, one per color , which allow color printing. The printing speed is around 120 characters per second.

6. Laser Printers:

• In laser printer an electronically controlled laser beam traces out the desired character to be printed on a photo conductive drum
• The drum attracts an ink toner on to the exposed areas.This image is transferred to the paper, which comes in contract with the drum. Very fast printers print 10,000 lines per minute. These printers give excellent outputs and can print a variety of fonts.
• Low speed laser printers, which can print 4 to 16 pages per minute, are now very popular.