Output Devices of Computer

Output Devices

Output Devices work as just in the reverse manner than the input device. We feed data in the Computer by typing on the keyboard of the Computer. Similarly information coming out of the Computer can be typed on the sheets of the paper by an output unit known as Printer. The output coming from the CPU is in the form of electronic binary signals which needs conversion in the same forms which can be easily understood by the Human Beings i.e. graphical, alphanumeric in human language, audio visual. This function is performed by Output Units. When the data has been processed by the CPU and converted into the information, the results are shown in the form of electronic signals. Output units convert them into a form which could be easily understood by us.

The Output can be given:

• On the screen by Visual Display Units
• In printed forms by Printers
• In graphic form by plotters
• In audible sound form by speech synthesizers
• Through other output units

Output devices may adopt different shapes and styles. The may be in form of typed, printed or sketched matter or may be visible or audio type.

But we can broadly classify them as:

• Hard Copy Device
• Soft Copy Device

By Hard Copy we mean output in direct usable form that is in printed or plotted form. Whereas soft copy is in magnetic/audible form that cannot be used directly.

Hard copy device produce a permanent record on media, such as paper sheets or paper tape. Soft-copy device do not produce a permanent record, but some soft-copy devices incorporate a printer for hard copy. Hard copy devices are very slow in operation as compared to soft copy devices.

Following Hard Copy Devices are very popular:

• Printers
• Plotters

Following soft copy devices are very popular:

• Visual display soft copy devices are very popular
• Liquid Crystal Display (LCD)
• Audio Response Unit

1.          Visual Display Unit (VDU)

The other common name of visual display unit is Monitor. Monitor looks like a television. It has a screen on which programs, commands, pictures, or graphical objects are displayed. When something is typed or keyed through keyboard, it displays the character or words on the screen. If a graphic is designed with the help of a mouse, it appears on the monitor’s screen.

The Cathode Ray Tube (CRT) is inside the Monitor. The screen is attached to it. Television also has the same cathode ray tube, which is also known as picture tube. There are various types of monitors available in the market, which can be attached to a computer for producing output.

Monochrome Monitor

Monochrome monitor displays only a single color, usually black or green on white background. International Business Machines (IBM’s) first personal computers had monochrome monitors. A person can see these monitors on railway station reservation counters.

Color Graphics Adapter (CGA) Monitors

This kind of monitor displays the colors red, green and blue. CGA were the first IBM color monitors. Due to the old techniques, these color monitors were not producing very natural colors.

Video Graphics Array (VGA) Monitors

These monitors can display 16 colors as well as 26 colors at one time.

Super Video Graphics Array (SVGA) Monitors

These monitors are better than VGA and produces better quality pictures. They still display 256 colors, but the colors are much sharper. SVGA uses more pixels (56% more) than VGA. These monitors were introduced by a group of American Companies in 1998.

2.            Printers

Printer is a hardware device that produces text or graphics output on the paper. Printer prints the information processed by the counter onto a piece or several pieces of paper. A hardcopy is that piece of paper that a printer prints on. Printers vary in size, style, printing speed, output capabilities price and resolutions.

Printers are grouped broadly into either impact or non-impact printers.

The examples of Impact printers are: Dot Matrix, Chain, Drum, Daisy, Wheel etc. 

and the examples of Non-Impact Computers are: Inkjet, Thermal and Laser etc.

Character Printer

These are slow speed printers, which print one character a time like typewriter. Generally these printer moves left to right for printing, but there are printers that can print information, while moving in both directions. In this class, following three types of printers are used.

Dot matrix Printer:

A dot matrix Printer uses the concept of dot printing characters or digits. These are faster than the character printers and can print graphics also. These printers are available in 2 sizes: 80 columns and 132 columns. Usually their speed is in the range of100 Characters per second (cps) to800 cps.

Daisy Wheel Printer:

It works on entirely different concepts and principals. This has a round print wheel with all the characters. Daisy Wheel Printer makes sharper images on the page, but its cost is higher. These printers can print up to 60 characters per sec.

Ink-jet Printers:

These are non-impact character printers based on a relatively new technology. They print character by spraying small drops of ink on to the paper. Inkjet printers produce high quality output because the characters are formed by dozen of tiny ink dots.  

Line Printers

Line printer prints one complete line at a time. These printers are fast as compared to character printers and can prints 100 to 3000 lines per minute. There are two types of line printers. They are Chain printer and Drum printer. Speed of line printer is limited by the speed of paper movement. A special type of paper is used, which holds electro-static charge in the form of spot.

Chain printer:

They use a rapidly moving chain called print chain. Each link of the chain is a character font. Instead of chain, some models of printers use a metal band having raised print character on it. The speed of Chain Printer ranges from 400-2500 characters per minutes.

Drum Printer:

There is a solid cylindrical drum in this type of Printer, where all the characters are printed. During its rotation, whenever a character appears in front of its printing position, then drum strikes the ribbon, ribbon strikes the paper and character gets printed on the paper.

Page Printer

These printers print information, coming from CPU after processing, page by page. These are the fastest printers developed so far. The early printers available in this category are the laser printer.

Laser Printer:

A high-resolution printer, typically 300 dpi (dots per inch), which uses electrostatic techniques and laser beams  to produce images. A laser beam of heat and a drum make black toner stick to paper to make it print. Dry powder ink, usually referred to as toner, is attracted to the charged area and forms the appropriate image. Laser printers are frequently used with PCs, to provide high quality output. Print speeds are in the range of 5-10 pages per minute for text, and much slower for graphics.

Writer: Mr. Krishan Kumar Saini


Today we have learnt about the Output Devices of Computer. Hope this lesson is helpful for you.