INPUT AND OUTPUT DEVICES

 An input device sends information to a computer and an output device receives information from a computer. For example, as you can see in the image, a keyboard sends electrical signals to your computer which display text or tell the computer to perform a function. Then in the lower half, you can see a computer sending data to a printer that will be reproduced on a piece of paper.

More examples

An input device, such as a computer keyboard or mouse, can send information (input) to the computer, but it cannot receive information (output) from the computer.

An output device, such as a computer monitor or printer, can receive information (output) from the computer, but it cannot send information (input) to the computer.

An input/output device, such as a CD-RW drive or USB flash drive, can both send information (input) to a computer and receive information (output) from a computer.

The devices which are used to input the data and the programs in the computer are known as “Input Devices”. or  Input device can read data and convert them to a form that a computer can use. Output Device can produce the final product of machine processing into a form usable by humans. It provides man to machine communication. Some of the I/O devices are explained below:

Input Devices:

a)      Graphics Tablets

b)      Cameras

c)      Video Capture Hardware

d)     Trackballs

e)      Barcode reader

f)       Digital camera

g)      Gamepad

h)      Joystick

i)        Keyboard

j)        Microphone

k)      MIDI keyboard

l)        Mouse (pointing device)

m)    Scanner

n)      Webcam

o)      Touchpads

p)      Pen Input

q)      Microphone

r)       Electronic Whiteboard

(1) Keyboard : Keyboard is used in the input phase of a computer-based information system. Keyboard is most common input device is used today. The data and instructions are input by typing on the keyboard. The message typed on the keyboard reaches the memory unit of a computer. It’s connected to a computer via a cable. Apart from alphabet and numeral keys, it has other function keys for performing different functions.

It consists of a set of keys mounted on a board.

Alphanumeric Keypad

It consists of keys for English alphabets, 0 to 9 numbers, and special characters like +

− / * ( ) etc.

Function Keys

There are twelve function keys labeled F1, F2, F3… F12. The functions assigned to

these keys differ from one software package to another. These keys are also user

programmable keys.

Special-function Keys

These keys have special functions assigned to them and can be used only for those

specific purposes. Functions of some of the important keys are defined below.

Enter

It is similar to the ‘return’ key of the typewriter and is used to execute a command or

program.

Spacebar

It is used to enter a space at the current cursor location.

Backspace

This key is used to move the cursor one position to the left and also delete the

character in that position.

Delete

It is used to delete the character at the cursor position.

Insert

Insert key is used to toggle between insert and overwrite mode during data entry.

Shift

This key is used to type capital letters when pressed along with an alphabet key. Also

used to type the special characters located on the upper-side of a key that has two

characters defined on the same key.

Caps Lock

Cap Lock is used to toggle between the capital lock features. When ‘on’, it locks the

alphanumeric keypad for capital letters input only.

Tab

Tab is used to move the cursor to the next tab position defined in the document. Also,

it is used to insert indentation into a document.

Ctrl

Control key is used in conjunction with other keys to provide additional functionality

on the keyboard.

Alt

Also like the control key, Alt key is always used in combination with other keys to

perform specific tasks.

Esc

This key is usually used to negate a command. Also used to cancel or abort executing

programs.

Numeric Keypad

Numeric keypad is located on the right side of the keyboard and consists of keys

having numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This

keypad is provided to support quick entry for numeric data.

Cursor Movement Keys

These are arrow keys and are used to move the cursor in the direction indicated by the

arrow (up, down, left, right).

 

(2) Mouse : It’s a pointing device. The mouse is rolled over the mouse pad, which in turn controls the movement of the cursor in the screen. We can click, double click or drag the mouse. Most of the mouse’s have a ball beneath them, which rotates when the mouse in moved. The ball has 2 wheels of the sides, which in turn mousse with the movement of the ball. The sensor notifies the speed of its movements to the computer, which in turn moves the cursor/pointer on the screen.

 (3) Scanner : Scanners are used to enter information directly in to the computers memory. This device works like a Xerox machine. The scanner converts any type of printed or written information including photographs into digital pulses, which can be manipulated by the computer.

 

(4) Track Ball : Track ball is similar to the upside- down design of the mouse. The user moves the ball directly, while the device itself remains stationary. The user spins the ball in various directions to effect the screen movements.

(5) Light Pen : This is an input device which is used to draw lines or figures on a computer screen. It’s touched to the CRT screen where it can detect raster on the screen as it passes.

2.  An output device

Any device that outputs information from a computer is called, not surprisingly, an output device. Since most information from a computer is output in either a visual or auditory format, the most common output devices are the monitor and speakers.

Some examples include headphones, printers, projectors, lighting control systems, audio recording devices, and robotic machines.

EXAMPLE OF OUTPUT DEVICES:

1.       Monitor

2.      Printers (all types)

3.      Plotters

4.      Projector

5.      LCD Projection Panels

6.      Computer Output Microfilm (COM)

7.      Speaker(s)

8.     Braille embosser

9.      Braille reader

10.  Flat panel

11.   GPS

12.  Headphones

13.  Computer Output Microfilm (COM)

14.  Sound card

15.   Speakers

16.  Speech-generating device (SGD)

17.   TV

18.  Video card

MONITOR

To display result or output from computer, a T.V like device is used which is called monitor. The monitors are also referred as C.R.T (Cathode Ray Tube), V.D.U (Visual Display Unit). The monitor assist during input from the keyboard, this display is called a soft copy. The monitor can be of various kinds, depending on the type of application. Monitors are categorized into two groups:

            I.      Monochrome monitors

           II.     Colour monitors

    I.      . MONOCHROME MONITORS

Monochrome monitors are used specially for text editing purpose. These monitors can display only one colour. Normally amber, green or paper white.

 II. COLOUR MONITORS

Colour monitors serves a wide range of selection according to the application. Such as red, green, blue, Enhance Graphic Array (EGA), Colour Graphic Array (CGA), Video Graphics Array (VGA), Super Video Graphics Array (SVGA).

There are two types of colour monitors:

i. CRT Monitor

ii. LCD Monitor

i. CRT MONITOR

The CRT monitors are a lot like television set, using the same CRT or Cathorde Ray Tube technology. The CRT monitor has two major parts; the screen and the cathode ray tube (CRT). The screen is the front of the monitor and CRT is fitted inside the monitor.

ii. LCD OR FLAT PANEL MONITOR

Another monitor type is LCD or Liquid Crystal Display. LCD monitors are a lot like CRT monitors without the bulkiness but they do not have CRT. LCD monitors use a flat lightweight surface filled with millions of tiny glass bubbles, each having a phosphoric covering. These phosphoric coverings glow to create an image. LCD screens provide clarity and flicker-free viewing.

PLOTTER

Plotter is a special output device, which is used to produce high quality, perfectly proportional hard copy output. Plotters are designed to produce large drawings or images such as construction plans for buildings or blue prints for mechanical devices. Plotters have been used in automotive and aircraft design, topological surveys, architectural layouts and other similar complex drafting jobs.

A plotter is composed of a pen, a move-able carriage, a drum and a holder for chart paper. Both the pen and the paper can move up and down and back and forth. This permits very detailed drawings. Some plotter having coloured pens can make coloured drawings also.

There are two types of plotters, which are as follows:

1. Drum Plotter

2. Flatbed Plotter

1. DRUM PLOTTER

On the drum plotter, the pens, and the drum move concurrently in different axes to produce the image. Drum plotters are used to produce continuous output, such as plotting earthquake activity, or for long graphic output, such as structural view of a skyscraper.

2. FLATBED PLOTTER

On some flatbed plotters, the pen moves in both axes while the paper remains stationary. However, on most desktop plotters, both paper and pen move concurrently in much the same way as on drum plotters.

A printer is an output device that prints paper documents. This includes text documents, images, or a combination of both. The two most common types of printers are inkjet and laser printers. Inkjet printers are commonly used by consumers, while laser printers are a typical choice for businesses. Dot matrix printers, which have become increasingly rare, are still used for basic text printing.

The printed output produced by a printer is often called a hard copy, which is the physical version of an electronic document. While some printers can only print black and white hard copies, most printers today can produce color prints. In fact, many home printers can now produce high-quality photo prints that rival professionally developed photos. This is because modern printers have a high DPI (dots per inch) setting, which allows documents to printed with a very fine resolution.

IMPACT PRINTING
Is the method used by the conventional type writers. In some type of impact printing a metal “hammer” embossed with a character strikes a print ribbon, which presses the characters image into paper. In other types the hammer strikes the paper and presses it into the ribbon characters created through impact printing can be formed by either a solid font or dot matrix printing mechanism.

NON – IMPACT PRINTING
Does not depend on the impact of metal on paper. In fact no physical contact at all occurs between the printing mechanism and the paper. The most popular non-impact methods today utilize thermal transfer, ink-jet.

TYPES OF PRINTERS

1. DOT MATRIX PRINTER
Any printer that produces character made up of dots using a wire pin printed head. The quality of output from a dot matrix printer depends largely on the number of dots in the matrix, which might be low enough to show individual dots or might be high enough to approach the look of fully formed characters. Dot matrix printers are often categorized by the number of pins in the printer head typically, 9 or 24.

2. LINE PRINTERS
Any printer that prints one line at one time, as opposed to one character at a time or one page at a time. Line printer typically produce the 11 by 17 inch “computer” printout. They are high speed devices and are often used with mainframes, minicomputers, or networked machines rather than with single user system. Types of line printers include chain printers and band printer.

3. LASER PRINTERS
An electrophotographic printer that is based on the technology used by photocopiers. A focussed laser beam and a rotating mirror are used to draw an image of the desired page on a photosensitive drum. This image is converted on the drum into an electrostatic charge, which attracts and holds toner. A piece of electrostatically charged paper is rolled against the drum, which pulls the toner away from the drum and onto the paper. Heat is then applied to fuse the toner to the paper. Finally, the electrified charge is removed from the drum and the excess toner is collected. By omitting the final step and repeating only the toner application and paper handling steps, the printer can make multiple copies.

4. DAISY WHEEL PRINTER
Daisy wheel printer are some times called letter quality printer because they are often used to produce attractive correspondence. The D.W.P is a flat circular device made of metal with character embossed on it. As this wheel spins at a very high speed the hammer hits the specific character against the ribbon which presses against the paper.

5. THERMAL TRANSFER PRINTER
It is a kind of non-impact printer. In electrothermal printing, characters are burned on to a special paper by heated rods on a print heat. They transfer ink from a wax-based ribbon onto plain paper. These printer can support high quality graphic.

6. INK – JET PRINTER
It is a kind of non-impact spray small dots of electrically charged ink onto a paper to form images. Ink jet printer are flexible enough to be used as plotters.

A braille reader, also called a braille display, is an electronic device that allows a blind person to read the text displayed on a computer monitor.

Imp Tip: Keep in mind that drives such as a CD-ROM, DVD, and a Floppy diskette drive may be capable of sending the computer information, but they are not output devices. These are considered storage devices.

Objective Questions

Question 1.

Which of the following input devices would be best suited to capturing images for use with a personal computer?

          

(1)   Optical mark reader

(2)   Digital camera

(3)   Touch screen

(4)   Graphics tablet

(5)   None of these

A. (2)

Question 2.

Which output device is suited to presenting information that is likely to change very frequently?

(1)   COM

(2)   Plotter

(3)   Printer

(4)   Monitor

(5)   Sound card

  A. (4)

Question 3.

Which of the following might be used to input and interpret information printed on bank cheques?

(1)   OCR

(2)   CAD

(3)   COM

(4)   MICR

(5)   OMR

  A. (4)

Question 4.

Which type of printer works by using a charged drum to deposit particles of ink on the paper?

(1)   Laser printer

(2)   Dot-matrix printer

(3)   Inkjet printer

(4)   Thermal printer

(5)   Daisywheel printer

  A. (1)

Question 5.

Which of the following storage devices is suited to holding large volumes of data that is unlikely to change often?

(1)   Magnetic tape

(2)   Floppy disk

(3)   Memory (RAM)

(4)   CD-ROM.

(5)   Hard disk

 A. (4)

Question 6.

Which of the following storage devices is normally used to store the computer’s operating system, application software and data?

(1)   Memory (RAM)

(2)   Floppy disk

(3)   Hard disk

(4)   CD-ROM

(5)   Magnetic tape

 A. (3)

Question 7.

In terms of computer storage, which of the following represents the largest unit of measurement?

(1)   Byte

(2)   Kilobyte (Kb)

(3)   Gigabyte (Gb)

(4)   Megabyte (Mb)

(5)   Bit

 A. (3)

Question 8.

The concept of ‘zero administration’ is associated with:

(1)   desktop computers

(2)   network computers

(3)   mini computers

(4)   portable computes

(5)   PDAs and organisers

 A. (2)

Question 9.

The hardware component used to control the operation of a computer system is:

(1)   processor

(2)   RAM

(3)   keyboard

(4)   hard disk

(5)   monitor

 A. (1)

Question 10.

The hardware component used for temporary storage of data and applications for processing is:

(1)   hard disk

(2)   RAM

(3)   processor

(4)   keyboard

(5)   monitor

 A. (2)