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 Input Devices

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shaista



Posts : 49
Join date : 2012-11-09

PostSubject: Input Devices    Sun Sep 08, 2013 7:17 pm

Input devices are used to get data into a system or it is a piece of hardware that is used to enter data into a computer. There are different kinds of input devices. We can use some input devices, such as keyboard, mouse etc to enter data by hand, it is called as manual input device. Other input devices such as bar code readers, MICR etc allow automated data entry; it is called as automatic input device.

1. Keyboard:
it is the most commonly and widely using input device. It is made up of buttons called 'keys'. The keys are arranged into sections:

· alphabet keys

· Function or F keys (F1, F2, F3)

· Numeric keys (one set above the alphabet keys and a numeric keypad on the right)

· Arrow keys

Command keys (insert, delete, home, end, page up/down)

A standard keyboard is called a QWERTY keyboard because of the arrangement of the letters of the top row of the alphabet keys.

Advantages

· Most computers come with a keyboard supplied.

· People are used to using keyboards to enter data, they need very little training.

· A skilled typist can enter data very quickly.

· Specialist keyboards are available e.g. ergonomic, gaming keyboards.

Disadvantages

· It is easy to make mistakes when typing in data.

· If you can't touch type, it can be time consuming to enter data.

· Keyboards are not suitable for creating diagrams.

· Disabled people often find keyboards difficult to use.

· Excessive use can lead to R.S.I.( Repetitive Strain Injury).

2. Mouse:

A mouse is also called a 'pointing device' because it enables you to control what happens on the screen by moving the mouse on your desk and pointing, clicking and selecting items on the screen.

A mouse usually has two buttons, a right and left one and also a central wheel which allows you to scroll up and down the page.

Advantages

Ideal for use with desktop computers.
Usually supplied as part of a new computer system.
Most computer users are familiar with them and require little training.
Works well in conjunction with a keyboard for data entry.

Disadvantages

They need a flat space close to the computer
The rollers in mice that use balls can become clogged with grease and grime and lose their accuracy until cleaned.
Overuse can lead to RSI.


3. Touch sensitive pad:

A touch sensitive pad or track pad is an input device which is usually found on a laptop computer. A touchpad can be used in place of a mouse. There are usually two buttons next to the touchpad which are used to replace the left and right mouse button.

Advantages

Useful for laptops when using a mouse isn't practical
The pad's position is fixed compared to the keyboard, unlike with a traditional mouse
Very short finger movements are required to move the cursor

Disadvantages

Takes practice and skill to control the position of the cursor using the touchpad
Moist, sweaty fingers can disrupt the signals picked up by the sensors.

4. Joystick:

Joysticks are mainly used for games. Whenever the stick is moved, the cursor moves in a similar direction on the screen.

Advantages

They give a better gaming experience for racing or flying styles of computer games

Disadvantages

Some people find joysticks more difficult to control than a traditional mouse.
Joysticks can break easily if too much force is used on them.

5. Digital Camera:

A digital camera records images electronically on a memory card rather than on film as did the older models of camera. The images can be downloaded from the memory card onto a computer and then printed, stored or manipulated with a photo editing application.

Most digital cameras let you view the image as soon as you have taken the picture; if you don't like what you see, it can be deleted. The quality of the image is dependent on the resolution or the number of pixels. The more pixels, the better the quality and clarity of the image. Many digital cameras are now capable of taking short video clips along with sound.

Advantages

No film is needed, no developing costs to view the pictures
Images can be viewed immediately and unwanted images can be deleted
Images can be edited, enlarged or enhanced
Images can be incorporated into documents or added to web sites
Extra memory sticks can be purchased to store images

Disadvantages

Digital cameras are generally more expensive than ordinary cameras which use film
When the memory is full, the images must be downloaded to a computer or deleted before any more can be taken.

6. Microphone:

A microphone can be used to input sound.

The sound is detected by the microphone and an electrical signal is transmitted to the computer. Special hardware is used to convert this analogue data into digital data so it can be stored and manipulated.

In the last few years a number of voice recognition systems have been developed. These packages let the user dictate the text into a computer and then convert the speech to text.

Dictating like this can be much quicker than typing but the software isn't perfect and it can interpret a word incorrectly.

7. Scanner:

Scanners can be used to convert images or text on paper into a digital format that can be used by the computer.

A scanner works by shining a beam of light onto the surface of the object that you are scanning. This light is then reflected back onto a sensor that detects the colour of the light. This is then used to build up the digital image.

Items that are scanned are usually stored in an image format. However, special software - Optical Character Recognition - can be used to convert text on the paper into text which can be edited with a word processor. However, the text doesn't always get converted very well and you could end up with a lot of mistakes.

There are two types of scanner:

Flatbed scanners
Handheld scanners

The most popular type is the flatbed scanner. This is probably the one that you use at school. They can scan larger images and are more accurate than handheld scanners.

Handheld scanners are usually only a few inches wide and are held in the hand whilst they are rolled across the document to be scanned. The images produced are generally not as large or as high quality as those captured with a flatbed scanner.

Advantages

Flatbed scanners are very accurate and can produce reasonably high quality images
Any image which is digitised by the scanner can then be included on electronic documents
Images once digitised can be enhanced with a graphics application

Disadvantages

Images can take up a lot of memory space
Images lose some quality in the scanning and digitising process
The quality of the final image is dependent on the quality of the original image.


8. Touch Screen:

A touch screen is the only device which works as both an input and an output device. You view the options available to you on the screen (output) and you then use your finger to touch the option that you have chosen (input).

Touch screens are easy to use and are often found in public places such as cash points at banks, ticket collection terminals at theatres or airports, information centers at museums.

Advantages

Easy to use, don't need much training
No extra peripherals such as a mouse are needed
Software can alter the screen while it is being used, making it more flexible than a concept keyboard which has a permanent overlay.

Disadvantages

Not suitable for inputting large amounts of data
Not very accurate - selecting detailed objects can be difficult with fingers
Tiring to use for long periods
More expensive than alternatives such as a mouse

9. Graphic tablets:

Graphics tablets are often used by graphics designers and illustrators.Using a graphics tablet, a designer can produce much more accurate drawings on the screen than they could with a mouse or other pointing device. Drawings created using a graphics tablet can be accurate to within hundredths of an inch.

A graphics tablet consists of a flat pad (the tablet) on which you draw with a special pen. As you draw on the pad, the image is created on the screen.

Advantages

It is much more natural to draw diagrams with a pencil type implement (the stylus) rather than with a mouse
A great level of accuracy can be achieved

Disadvantages

Not really suitable for general selection work such as pointing and clicking on menu items
Graphics tablets are much more expensive than a mouse.



10. Concept Keyboard:

A concept keyboard is a flat board that contains a grid of buttons. Each button can be programmed to do whatever you want.

An overlay sheet with pictures or symbols is placed on the grid so that the user can tell what pressing on different areas will do.

Concept keyboards are used when fast input is needed and are ideally suited to selecting from a limited range of choices such as fast food restaurants.

Advantages

Much faster for making non-text selections such as menu choices on the till of a fast-food outlet.
The keyboard is waterproof which can be useful where there is dirt or the risk of splashes

Disadvantages

Poor for text or numeric input - although some keyboards do include a numeric keypad so the operator can enter the amount sold.
Limited to the options shown on the keyboard.


11. Tracker ball:

Tracker ball is like an upside down mouse.

The advantage of a tracker ball is that it takes up much less space.

Tracker ball are often seen on laptop computers.


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