Output is the result of processes that are done on the computer. An output device receives information from the computer and translates it from machine language to a form that humans can read or so that another machine can read the information. Output that is readable by the user can be categorized into two categories: hard copy or soft copy. Hard copy is a relatively permanent form of output that can be read immediately or stored for later use, such as paper. Printers are the most common hard copy output devices. Soft copy is a transient form of output, for example, text on a screen display. It is lost when the computer is turned off unless it is saved in the main memory or on a disk

NAMES OF SOME OUTPUT DEVICES ARE GIVEN BELOW:- PRINTERS

MONITORS

SPEAKERS

HEADPHONES

PLOTTER

PROJECTORS

A most convenient and useful method by which the computer can deliver information is by means of printed characters. Printers can be divided into two distinct categories :

IMPACT PRINTERS: In these printers, there is a mechanical contact between the print head and paper.

NON IMPACT PRINTERS: In these printers, there is no mechanical contact between the print head and paper.

i. Drum Printers- It consist of cylindrical drum on which characters are embossed for each & every print position on line. Drum is rotated at very high speed. Character is printed by striking hammer against embossed character on surface.

ii. Chain Printers- It has characters engraved in type assembled on a chain. With the rotation of band, hammer is activated when desired character comes in front of it.

iii. Dot Matrix printer- print head contains a vertical array of pins. As the print head moves across the paper, selected pins fire against the ribbon. The more pins the print head has the better will be the printing quality.

1. Electromagnetic printers- they use magnetic recording techniques. Required output is written on a drum surface, which comes into contact with the magnetic powder that adheres to the charged areas. The powder is then pressed onto the paper.

2. Inkjet printers- It uses a continuous stream of ink drops to print characters on paper. The print head contains tiny nozzles that spray drops of ink on the paper. The quality is good because the characters are formed by dozens of tiny ink drops.

3. Thermal Printers- It uses a special heat-sensitive coated paper. When a spot on the paper passes under the print head, it gets heated. This turns the coating in that area black, producing the image of the character on the paper.

4. Laser Printers- They print one page at a time. The output image is written on a copier drum with the help of an electrically charged light beam. These attract the toner ink particles which are then deposited on and fixed to paper using heat or pressure.

DISPLAY UNITSDISPLAY UNITS

LIQIUD CRYSTAL LIQIUD CRYSTAL DISPLAY (LCD)DISPLAY (LCD)

CATHODE RAY TUDE CATHODE RAY TUDE (CRT) (CRT)

DIGITAL MONITORSDIGITAL MONITORS VIRTUAL DISPLAYVIRTUAL DISPLAY MULTIPLE MONITORSMULTIPLE MONITORS

LIQIUD CRYSTAL DISPLAY LIQIUD CRYSTAL DISPLAY

Passive LCD produce poor contrast, slow Passive LCD produce poor contrast, slow response, and other image defects. response, and other image defects.

These were used in most laptops until the mid These were used in most laptops until the mid 1990s .1990s .

Thin Film Transistor LCD‘s give much better LCD‘s give much better picture quality in several respects. picture quality in several respects.

size

CATHODE RAY TUBECATHODE RAY TUBE

Raster scan computer monitors, which produce Raster scan computer monitors, which produce images using pixels .images using pixels .

Television sets were used by most early sets were used by most early personal and home computers, connecting personal and home computers, connecting composite video to the television set using a to the television set using a modulator. .

DIGITAL MONITORSDIGITAL MONITORS

Early digital monitors Early digital monitors are sometimes known as are sometimes known as TTL’s because the TTL’s because the voltages on the red, voltages on the red, green, and blue inputs green, and blue inputs are compatible with are compatible with TTL logic chips . logic chips .

They are capable of They are capable of displaying 32-bit displaying 32-bit grayscale at 1024x768 grayscale at 1024x768 resolution .resolution .

VIRTUAL DISPLAYVIRTUAL DISPLAY

Screenshot of the Screenshot of the Spaces environment under environment under Mac OS X.Mac OS X.

Much software and video hardware support Much software and video hardware support the ability to create additional, virtual pieces of the ability to create additional, virtual pieces of desktop, commonly known as desktop, commonly known as workspacesworkspaces..

MULTIPLE MONITORSMULTIPLE MONITORS

Two Apple flat-screen Two Apple flat-screen monitors used as an monitors used as an extended desktop . .

More than one monitor can More than one monitor can be attached to the same be attached to the same device. device.

The more sophisticated of The more sophisticated of the two, the two, extensionextension allows allows each monitor to display a each monitor to display a different image, so as to different image, so as to form a contiguous area of form a contiguous area of arbitrary shape. arbitrary shape.

Computer speakers, or multimedia speakers, are external speakers, commonly equipped with a low-power internal amplifier. Computer speakers range widely in quality and in price. The computer speakers typically packaged with computer systems are small plastic boxes with mediocre sound quality. Some of the slightly better computer speakers have equalization features such as bass and treble controls, improving their sound quality somewhat. The internal amplifiers require an external power source, known as a 'wall-wart'. More sophisticated computer speakers may have a 'subwoofer' unit, to enhance bass output, and these units usually include the power amplifiers both for the bass speaker, and the small 'satellite' speakers

SPEAKERSSPEAKERS

LOUDSPEAKERLOUDSPEAKER DRIVER TYPESDRIVER TYPES WOOFERWOOFER ENCLOSURESENCLOSURES DIGITAL SPEAKERSDIGITAL SPEAKERS

LOUDSPEAKERLOUDSPEAKER

A A loudspeakerloudspeaker, , speakerspeaker, or , or speaker systemspeaker system is an is an electromechanical electromechanical transducer that converts an transducer that converts an electrical signal to sound .electrical signal to sound .

most loudspeaker systems most loudspeaker systems require more than one require more than one driver, particularly for high driver, particularly for high sound pressure level sound pressure level

WOOFERWOOFER

A A woofer is a driver that is a driver that reproduces low reproduces low frequencies .frequencies .

Additionally, some Additionally, some loudspeakers use the loudspeakers use the woofer to handle middle woofer to handle middle frequencies, eliminating frequencies, eliminating the mid-range driver .the mid-range driver .

ENCLOSURESENCLOSURES

Most loudspeaker systems Most loudspeaker systems consist of drivers mounted consist of drivers mounted in an in an enclosure, or cabinet , or cabinet

The role of the enclosure is The role of the enclosure is to provide a place to mount to provide a place to mount the drivers and to prevent the drivers and to prevent sound waves from the back sound waves from the back of a driver from interfering of a driver from interfering destructively destructively

DIGITAL SPEAKERSDIGITAL SPEAKERS

Digital speakers have been the subject of Digital speakers have been the subject of experiments by Bell Labs as far back as the experiments by Bell Labs as far back as the 1920s. 1920s.

The term "digital" or "digital-ready" is often The term "digital" or "digital-ready" is often used for marketing purposes on speakers or used for marketing purposes on speakers or headphones .headphones .

                

              

Headphones are a pair of small loudspeakers, or less commonly a single speaker, with a way of holding them close to a user's ears and a means of connecting them to a signal source such as an audio amplifier, radio or CD player. They are also known as earphones, ear buds, stereo phones, headsets or, informally cans. In the context of telecommunication, the term headset is used to describe a combination of headphone and microphone used for two-way communication, for example with a telephone

A plotter is another hard copy output device that

reproduces graphic images on paper using a pen that is attached to a

movable arm. Multi coloured pen can also be used. Plotters are slow devices. The graphics

they produce are uniform and of very good quality. Plotters can be divided

into 4 typesDrum plotter,

Micrographic plotter, Inject plotter, Flatbed

plotter

A video projector takes a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for conference room presentations, classroom training, home theatre and live events applications. Projectors are widely used in many schools and other educational settings, connected to an interactive white board to interactively teach pupils