OUTPUT DEVICES


Following are few of the important output devices which are used in a computer

  • Monitor
  • Printer
  • Plotter

Monitor:

Monitors are the main output device of a computer.

It is commonly called as Visual Display Unit (VDU),

The term “monitor” is often used similarly with “computer screen” or “display.”

The monitor displays the computer’s user interface and open programs.

It allows the user to interact with the computer, using the keyboard and mouse.

It forms images from tiny dots, called pixels that are arranged in a rectangular form.

There are two kinds of viewing screen used for monitors.

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

 

Cathode-Ray Tube (CRT):

This technology is mainly used in televisions and computer display screens

The CRT display is made up of small picture elements called pixels.

A finite number of characters can be displayed on a screen at once.

Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

It is large in size and consumes very high power.

Flat- Panel Display:

A flat-panel display is a thin screen display found on all portable computers and is the new standard for desktop computers.

Instead of utilizing the CRT technology, flat-panel displays use Liquid-crystal display (LCD) technology to make them much lighter and thinner.

Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, graphics display.

 


Printer:

A printer is a piece of hardware for a computer.

It is a device which allows a user to print items on paper, such as letters and pictures.

To do its work, a printer must be connected to a computer.

There are mainly two types of printer.

  • Impact Printer
  • Non-Impact Printer

Impact Printer:

The impact printers print the characters by striking them on the ribbon which is then pressed on the paper.

Impact printing saw wide use in commercial data processing, personal desktop printing and early forms of word processing.

They are famous for their unique features, commonly used in businesses where multi-part forms are printed.

There are different types of Impact printer.

  • Dot Matrix Printer
  • Letter Quality Printer

Dot Matrix Printer:

The dot-matrix printer uses print heads containing from 9 to 24 pins.

These pins produce patterns of dots on the paper to form the individual characters.

Dot-matrix printers are relatively expensive and do not produce high-quality output.

Letter Quality Printer:

These printers use a single print element known as a Daisy Wheel.

A daisy wheel printer is an early type of impact Printer invented in 1969 by David S. Lee.

Daisy wheel printers are roughly the size of a typewriter.

The printer uses a metal or plastic disk containing each of the letters, numbers, and other characters it supports

These printers were popular in the 1970s and 1980s, but are no longer used because of they have a low quality of print, are very slow and loud.

Non-Impact Printer:

These printers do not hit or impact a ribbon to point.

They use laser, xerographic, electrostatic, and chemical and inkjet technologies.

There are different types of Non- Impact printer.

  • Line Printer
  • Page Printer

Line Printer:

The line printer is an impact computer printer that prints one entire line of text at a time. The line printer is a form of high speed impact printer.

A fast line printer can print as many as 3,000 lines per minute.

Large Computer systems typically use Line Printer.

The Line Printers are of two Types:

  • Drum Printer
  • Chain Printer

Drum Printer:

A drum printer consists of a solid, cylindrical drum that having rows of character moulded on its surface.

There are number of bands corresponding to number of printing positions.

Each band consists of all available characters.

There is a print hammer located behind the paper that strikes the paper, along with linked ribbon, against the proper character on the drum.

One revolution of the drum is required to print each line.

Here all characters on the line are not printed at exactly the same time, but the time required to print the entire line is quite less.

The drum printers are expensive than chain and are less flexible in terms of size of font.

They have speed in the range of 300 to 2000 lines per minute.

Chain Printer:

It consists of moving chain called a print chain on which characters are mounted that moves horizontally in front of the papers.

There is a print hammer located behind the paper for each possible print position.

To enhance the speed of the chain printers, the character set is repeated several times on chain

Thus chain must make a complete revolution to position the desired character in the correct position.

Page Printer:

These are non-impact, fastest and quietest printers that can produce documents at speed of 18,000 lines per minute.

These printers use non-mechanical techniques such as xerographic, laser and electrostatic called electrographic techniques.

Due to their extremely high cost, these printers are economical only when mass printing involving thousands of pages are to be printed frequently.

Most commonly Page Printers are:

  • Laser Printer
  • Thermal Printer

Laser Printer:

Laser Printers use a laser beam to form characters by projecting a dot matrix pattern onto drum surface.

These Printers use special memory to store the images for printing.

Laser Printers are moe expensive than all other printers.

They are faster than all other printers and their print quality is higher.

Single -Colour laser printers typically can produce between 4 and 16 pages of text a minute.

The laser printers have resolutions of 600 dpi, both horizontally and vertically.

But some advanced models have resolutions of 1200 dpi or 1800 dpi.

Laser Printers are suitable for office environments where several users can share the same printer easily via network.

Thermal Printer:

Plotter:

Plotters are used to produce large pictures or images such as drawing graphs, making maps, construction plans for buildings, plotting contour lines and detailing of civil engineering structure or blueprints for machine comonens.

They are basically of two types:

  • Drum Plotter
  • Flat-Bed Plotter

Drum Plotter: A drum plotter is also known as Roller Plotter. It roller on which a paper is placed and the drum rotates back and forth to produce the graph on the paper. This work is done under the control of computer. Drum Plotters are used to produce continuous output, such as plotting earthquake activity.

Flatbed Plotter: A flatbed plotter is also known as Table Plotter. It plots on paper that is spread and fixed over a rectangular flatbed table. It uses two robotic drawing arms, each of which holds a set of colored ink pens or pencils. Typically, the plot size is equal to the area of a bed. It is used in the design of cars, ships etc. Flatbed plotter is very slow in drawing or printing graphs. The main reason of the slow printing is due to the movement mechanical devices.

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