Computer Output Devices - Computer Fundamentals

What are output devices? Explain its functions?

Following are some of the important output devices used in a computer.

  • Monitors
  • Graphic Plotter
  • Printer


Monitors, commonly called as Visual Display Unit (VDU), are the main output devices of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness or the brightness of the image depends upon the number of pixels that are arranged. You can see any type of image on the screen.

There are two kinds of viewing screen used for monitors.

  • Cathode-Ray Tube (CRT)
  • Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. It clarity depends upon the size of the pixel, the smaller the pixel, the better the image clarity would be. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.


A definite number of characters can be displayed on a screen at once. The screen can be divided into a set of character boxes - fixed point on the screen where a standard character can be placed. Most of the screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT −

  • Large in Size
  • High power consumption

Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement compared to that of CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.


The flat-panel display is divided into two categories −

  • Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).
  • Non-Emissive Displays − Non-emissive displays are considered as the optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).


Printer is an output device, which is used to print information on paper.

There are two types of printers −

  • Impact Printers
  • Non-Impact Printers

Impact Printers

Impact printers first print the characters by striking them on the ribbon, which is then pressed on the paper.

Characteristics of Impact Printers are the following −

  • Very low costs
  • Very noisy
  • Useful for bulk printing due to low cost
  • Physical contact is required with the paper to produce an image

These printers are of two types −

  • Character printers
  • Line printers

Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

  • Dot Matrix Printer(DMP)
  • Daisy Wheel

Dot Matrix Printer

In the market, the most popular printer prevailing is Dot Matrix Printer. These printers are popular because of their printing comfort and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which displays out in the form of a character which is why it is called Dot Matrix Printer.



  • Very low cost
  • Extensively Used
  • Other language characters can be printed


  • Slow Speed
  • Poor Quality

Daisy Wheel

You can see the daisy wheel printer below where head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be displayed here and there with very nice quality.



  • More reliable than DMP
  • Good in quality
  • Fonts characters can be changed easily.


  • Slower than DMP
  • Very noisy
  • High in cost than DMP

Line Printers

Line printers are the printers which print one line at a time.


These are of two types −

  • Drum Printer
  • Chain Printer

Drum Printer

This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. These numbers of tracks should match with the size of the paper. i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can be able to print 300 to 2000 lines per minute.


  • Very high speed


  • High in cost.
  • Characters fonts cannot be changed

Chain Printer

In this printer, a chain of character sets is used; hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.


  • Character font size can be changed easily.
  • Different types of languages can be used with the same printer.


  • Very Noisy.

Non-impact Printers

Non-impact printers are the printers where the characters are printed without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

These printers are of two types −

  • Laser Printers
  • Inkjet Printers

Characteristics of Non-impact Printers

  • Faster than impact printers
  • They are not noisy
  • High in quality
  • Supports many fonts and different character size.

Laser Printers

These are non-impact page printers. They use laser lights to produce the dots which are required to form the characters that to be printed on a page.



  • Very high speed
  • Very high quality output
  • Gives good quality graphics
  • Supports many fonts and different character size


  • Expensive
  • Cannot be used to produce multiple copies of a document in a single printing.

Inkjet Printers

Inkjet printers are non-impact character printer works relatively with new technology. They print the characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

They make less noise because no hammering is done and these have many styles of printing modes. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.



  • High quality in printing
  • More reliability.


  • Very expensive as the cost per page is high due to the new technology.
  • Works very slow as compared to laser printer.

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