INPUT DEVICES

Input devices are those devices through which we can input data to the computer. Mostly used Input Devices are

1.Keyboard
2.Mouse
3.Touch Screen
4.Light Pen
5.Trackball
6.Touch Pad
7.Joystick
8.Scanner
9.Optical Recognitions
9.1.Optical Bar Recognition (OBR)
9.2.Optical Mark Recognition (OMR)
9.3.Optical Character Recognition (OCR)
10.Magnetic Ink Character Recognition (MICR)
11.Audio Visual input devices
11.1.Microphone and Speech Recognitions
11.2.Video input
11.3.Digital camera

1. Keyboard

Keyboard is typewriter-like input device consisting of set of keys that enable you to enter data into a computer. The keys on computer keyboards are often classified as follows:

i.Alphanumeric keys: Letters and Numbers, Tab, Caps Lock, Backspace, Enter.

ii.Punctuation keys: Comma, Semi Colon etc.

iii.Special Purpose keys: Insert, Delete, Esc, Print Screen, Scroll Lock, Pause, Start, Shortcut keys.

iv.Function keys: F1 – F12

v.Modifier keys: Shift, Ctrl, Alt keys

vi.Cursor movement keys: Arrow keys, Home, End key etc.

vii.Numeric key pad: 0 - 9

Alphanumeric keys are the general keys helps to make document. Punctuation keys helps to format the documents. Functional keys are named as F1, F2 etc. there are 12 such keys and they perform special functional like, to took help you can press F1, to power off the computer you can press the power point keys, similarly other keys are sleep keys, wake up keys etc. the combination of control keys and functional keys perform certain tasks like ALT+F4 keys close the windows. Functional keys are more powerful in UNIX operating system. Cursor movement keys are home (bring the cursor at starting of line), end (bring the cursor at the end of the line), page up (move one page up), page down etc.

Keyboards are of different of types: some keyboards have 101 keys and some have 84 keys. These days’ keyboards are manufacturing with more keys than previous. Most of the keyboard use QWERTY layout in which the first six keys on the row of letters are Q, W, E, R, T and Y. Other layout includes DVORAK layout in which the most commonly used alphabets like vowels (a, e, i, o, u) are arranged at the middle row of the keyboard. Nowadays the software for the keyboard allows us to choose among the many layouts available.

2. Mouse

Mouse is another input device or pointing device that controls the movement of the cursor or pointer on the display screen. Mouse is a small object easily rolled around a flat surface. Mouse helps to open, close and select files and other necessary operations. Mice contain at least on button and sometimes as many as three, which have different functions depending on what program is running. Mouse is important on graphical user interface user interface because you can simply points to options and clicks a button. Using mouse involves five techniques- pointing, clicking, double-clicking, dragging and right clicking.

Types of Mouse:
a) Mechanical: Mechanical has a rubber or metal ball on its underside that can roll in all directions. Mechanical sensors within the mouse detect the direction the ball in rolling and move the screen pointer accordingly.

b) Opto-mechanical: Opto-mechanical is same as a mechanical mouse but uses optical sensors (LEDs) to detect motion of the ball. There is horizontal and vertical roller inside the mouse. That roller helps to roll the mouse and calculate the coordinate points on the screen.

c) Optical Mouse: Optical Mouse uses a laser to detect the mouse’s movement. For this we must have a mouse along a special mat with a grid so that it can detect the movement of mouse through laser beam.

Mouse can be connected directly to the computers port or it might be wireless (infra red or radio waves to communicate with the computer).

3. Touch Screen

Touch Screen is a type of display screen that has a touch sensitive transparent panel covering the screen. Instead of using a pointing device such as a mouse or light pen, we can use our finger to point directly to objects on the screen.

4. Light Pen

Light Pen is an input that utilizes a light sensitive detector to select objects on a display screen. Light pen uses a light-sensitive photo-electric cell to communicate the screen position to the computer. When the light pen tip is placed against the screen, its light sensitive elements detect the light emitted from the screen. Nowadays, light pens are used in many big hotels’ room for the customer for selecting their choice of menu and other items.

5. Touch Pad

Many laptop computers use a touchpad in front of the keyboard. You move your finger on the pad to move the cursor on the screen. When you want to click, you can tap pad or use the buttons in front of the pad, which works like mouse buttons.

6. Trackball

The function of trackball is same as that of mouse but instead of moving a whole body of mouse, we can rotate ball and the body is fixed. It is like a mouse turned upside-down. There are usually one to three buttons next to the ball, which you use just like a mouse button. The advantage of trackball over mouse is that it is stationary hence does not occupy big area.

7. Joystick

A joystick has lever that moves in all directions and controls the movements of pointer. A joystick is similar to mouse, except that with a mouse the cursor stops moving as soon as you stop the mouse movement. With a joystick, the pointer continues moving in the direction the joystick is pointing. To stop a pointer movement you must return the joystick to upright to upright position. Most joysticks include two buttons called triggers.

8. Scanner

A Scanner is an input device that can read text or images printed on paper and translate the information into the form the computer can use. In other words a scanner copies an image, creates and stores it on a computer disk in a form that can be used by the computer. A scanner works by digitizing an image-dividing it into a grid of boxes and representing each box with either zero or one, depending on whether the box is filled in.

9. Optical Recognition

Optical recognition occurs when a device scans a printed surface and translates the image the scanner sees into a machine readable format that is understandable by the computer. Optical recognitions can be of following types.

9.1 Optical Mark Recognition (OMR): It employs mark recognition to scan and translate, based on its location which is a series of pen or pencil marks into computer readable form. An optical mark reader senses the pen or pencil marks by altering the intensity of light incident on the document and then sensing the reflected light received from the surface of the document. Intensity of reflected light received by a light sensor is less than that of the incident light due to the absorption by darker areas. Thus presence of a mark is registered by the intensity of reflected light received. These can be used to obtain the scores of the tests that use objective type multiple choice questions paper.

9.2 Optical Bar Recognition (OBR): A series of thin black bars we get in the back of books and products are called bar codes which are arranged to represent data, such as manufacturer name, product type etc. An optical bar code reader reads the bar codes and converts them into electrical pulses, which are sent to computer for processing. Usually Bar codes are universal code and uses standard code, which has vertical bars of varying widths- representing 10 digits. The first five digits represent the manufacturer and the second five digits identify the products.

9.3 Optical Character Recognition (OCR) [Optical Scanner]

An OCR is a direct entry input device, which can detect alphanumeric characters printed on any paper. A light source converts the alphabets, numbers and similar such characters into electrical signals which are then sent to the computer for procession. The text to be scanned should be illuminated by low frequency light source. The reflected light from the text is received by the light sensitive cells and generates the signals depending on the type of text.

10. Magnetic Ink Character Recognition (MICR)

MICR is an input device, which reads the characters that have been printed in magnetic ink. Magnetic ink is a special type of ink that contains iron oxide. The magnetic ink gets magnetized when data are entered using MICR. Then the MICR reads such magnetized patterns of written characters. For identifying those characters, they are compared with the patterns of corresponding characters stored in the memory. MICR is used by banks for processing credit cards that allows readers such as Automated Teller Machines (ATMs) to read account information and facilitate monetary transactions.

11. Audio Visual Inputs

11.1 Microphones and speech recognitions

Microphones are important input devices to record speech. Microphones together with sound cards and speakers can be used for audio conferencing and in phone dialers. The sound cards translate the analog signal or sound wave from microphones into digital codes the computer can store and process and vice-versa. This process is called digitizing.

Next is speech or voice recognition which is a process of translating the spoken words into text. This allows use to dictate to the computer instead of typing and give simple command like Open, Cancel etc. speech recognition software takes the smallest individual sounds in a language, called phonemes and translates them into text or commands.

11.2 Video input

Application such as video conferencing enable people to use full motion video images, captured by PC video camera, and transmits them to a limited number of recipients on a network or on internet. Videos are commonly used in web pages and presentations. The PC camera captures the images, digitizes it by breaking them into individual pixels. Each pixel characteristic are stored in digital codes which in turn are compressed so that they can be stored on disk or transmitted over network.

11.3 Digital Camera

They work like PC video camera but they are portable handheld devices that capture still images. They capture images electronically and digitize them, compress them to store on special memory card. The users can then copy the information to the PC where the image can be edited, copied, printed or transmitted to another user.