Input Device of Computer

Input device: An input device is any machine that feeds data into a computer. For example, a keyboard is an input device, where as a display monitor is an output device.

 Keyboard

Keyboard is an input device consisting of set of typewriter like keys that enable you to enter data into a computer. Computer keyboard are similar to electronic typewriter keyboard but contains additional keys. The keys on computer keyboards are often classified as follow:

Alphanumeric keys – letters and numbers

Punctuation keys – comma, period, semicolon, and so on

Special keys – function keys, control keys, arrow keys, Caps lock key and so on

The standard layout of letters, numbers and punctuation is known as QWERTY keyboard because the first five keys on the top row of letters spell QWERTY. There is no standard keyboard, although many manufacturers imitate the keyboards for PCs. There are actually three different PC keyboard: the original PC keyboard with 84 keys, the AT keyboard also with 84 keys and the enhanced keyboard with 101 keys. In addition to these keys, IBM keyboards contain the following keys: Page Up, Page Down, Home, End, Insert, Num Lock, Scroll Lock, Break, Caps Lock, and Print Screen.

 Mouse

Mouse is a device that controls the movement of the cursor or pointer on a display screen. A mouse is small object you can roll along a hard flat surface. Its name is derived from its shape, which looks bit like a mouse, its connecting wire that one can imagine to be the mouse’s tail. As you move the mouse, the pointer on the display screen moves in the same direction. Mice contains at least one button and sometimes as many as three, which have different function depending on what program is running. Invented by Doulas Engelbart of Standford research centre in 1963 and pioneered by Xerox in the 1970s. The mouse is one of the great breakthroughs in computer ergonomics because it frees the user to a large extent from using keyboard. The mouse is the important for graphical user interface because you can simply point to option and objects and click a mouse button. The mouse is also useful for graphics programs that allow you to draw pictures by using mouse like pen, pencil or paintbrush.

Mechanical mice

Bill English, builder of Engelbart's original mouse, invented the ball mouse in 1972 while working for Xerox PARC. The ball-mouse replaced the external wheels with a single ball that could rotate in any direction. It came as part of the hardware package of the Xerox Alto computer. Perpendicular chopper wheels housed inside the mouse's body chopped beams of light on the way to light sensors, thus detecting in their turn the motion of the ball.

Mechanical mouse, shown with the top cover removed

The ball mouse has two freely rotating rollers. They are located 90 degrees apart. One roller detects the forward–backward motion of the mouse and other the left–right motion. Opposite the two rollers is a third one (white, in the photo, at 45 degrees) that is spring-loaded to push the ball against the other two rollers. Each roller is on the same shaft as an encoder wheel that has slotted edges; the slots interrupt infrared light beams to generate electrical pulses that represent wheel movement.

Each wheel's disc, however, has a pair of light beams, located so that a given beam becomes interrupted, or again starts to pass light freely, when the other beam of the pair is about halfway between changes. Simple logic circuits interpret the relative timing to indicate which direction the wheel is rotating. The mouse sends these signals to the computer system via a data-formatting IC and the mouse cable. The driver software in the system converts the signals into motion of the mouse cursor along X and Y axes on the screen.

The ball is mostly steel, with a precision spherical rubber surface. The weight of the ball, given an appropriate working surface under the mouse, provides a reliable grip so the mouse's movement is transmitted accurately.

Ball mice and wheel mice were manufactured for Xerox by Jack Hawley, doing business as The Mouse House in Berkeley, California, starting in 1975.[14][15]

Optical mice

A wireless optical mouse on a mouse pad

An optical mouse uses a light-emitting diode and photodiodes to detect movement relative to the underlying surface, rather than internal moving parts as does a mechanical mouse. Connectivity and communication protocols

To transmit their input, typical cabled mice use a thin electrical cord terminating in a standard connector, such as RS-232C, PS/2, ADB or USB. Cordless mice instead transmit data via infrared radiation (see IrDA) or radio (including Bluetooth), although many such cordless interfaces are themselves connected through the aforementioned wired serial buses.

Serial interface and protocol

Standard PC mice once used the RS-232C serial port via a D-subminiature connector, which provided power to run the mouse's circuits as well as data on mouse movements.

PS/2 interface and protocol

For more details on this topic, see PS/2 connector.

With the arrival of the IBM PS/2 personal-computer series in 1987, IBM introduced the eponymous PS/2 interface for mice and keyboards, which other manufacturers rapidly adopted. The most visible change was the use of a round 6-pin mini-DIN, in lieu of the former 5-pin connector. In default mode (called stream mode) a PS/2 mouse communicates motion, and the state of each button, by means of 3-byte packets.[30] For any motion, button press or button release event, a PS/2 mouse sends, over a bi-directional serial port, a sequence of three bytes, with the following format:

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Byte 1 YV XV YS XS 1 MB RB LB Byte 2 X movement Byte 3 Y movement USB

The industry-standard USB protocol and its connector have become widely used for mice; it's currently among the most popular types.

Cordless or Wireless

A wireless mouse made for notebook computers

Cordless or wireless mice transmit data via infrared radiation (see IrDA) or radio (including Bluetooth). The receiver is connected to the computer through a serial or USB port. The newer nano receivers were designed to be small enough to remain connected in a laptop or notebook computer during transport, while still being large enough to easily remove.

 

 Trackball

Trackball is another pointing device. Essentially a track ball is a mouse lying on its back. To move the pointer you rotate the ball with your thumb, your fingers. There are usually one to three buttons next to the ball, which you use just like mouse buttons. The advantage of track ball over mice is that the trackball is stationary so it does not require much space to use it. In addition you can place a trackball on any surface. For both these reasons, trackball are popular pointing devices for portable computers.

 Joystick

A lever that moves in all directions and controls the movement of a pointer or some other display symbols. A joystick is similar to a mouse, except that with a mouse cursor stops moving as soon as you stop moving the mouse. With a joystick the pointer continues moving in the direction the joystick is pointing. To stop the pointer you must return the joystick to its upright position. Most joysticks include two buttons called triggers. Joysticks are used mostly for computer games, but they are also used for CAD/CAM systems and other applications.

Digitizing Tablet

This is an input device that enable you to enter drawing and sketches into computer. A digitizing tablet consists of an electronic tablet and a cursor or pen. A cursor is similar to a mouse, expect that it has a window with cross hairs for pinpoint placement, and it can have as many as 16 buttons. A pen also called a stylus which looks like a ball pen but uses an electronic head instead of ink. The tablet contains electronics that enable it to detect movement of cursor or pen and translate the movement into digital signals that it sends to computer. For digitizing tablets each point on the tablet represents a point on the display screen in a fixed manner. This differs from mice, in which all movement is relative to the current cursor position. The static nature of digitizing tablets makes them particularly effective for tracing drawing. Most modern digitizing tablets also support a mouse emulation mode, in which the pen or cursor acts like a mouse. Digitizing tablets also called digitizer, graphic tablets.

Scanner

Scanner is an input device that can read text printed on paper and translate the information into a form that the computer can use. A scanner works by digitizing an image – dividing it into a grid of boxes and representing each box with either zero or a one, depending on whether the box is filled in. (for colour and gray scaling the same principle applies, but each box is represented by up to 24 bits) The resulting matrix of bits called a bit map and can then be stored in a file, display on screen and manipulating by programs. Optical scanner do not distinguish text from illustrations; they represent all images as bit maps. Therefore, you cannot directly edit text that has been scanned. To edit text read by an optical scanner, you need an optical character recognition (OCR) system to translate the image into ASCII characters.

 Magnetic Ink Character Recognition (MICR)

Magnetic Ink Character Recognition (MICR) allow the computer to recognize characters printed using magnetic ink. MICR is a directly entry method used in banks. This technology is used to automatically read those frustrating looking numbers on the bottom of cheque. A special purpose machine known as reader/sorter reads characters made ink containing magnetized particles. A related technology is the magnetic strip, used on the back of credit cards and debit cards of bank, which allows reader such as automated teller machine to read account information and facilitate monetary transactions.

 Optical Character Recognition (OCR)

OCR refers to the branch of computer science that involves reading text from paper and translate the images into a form that the computer can manipulate ( for example, into ASCII codes). An OCR system enables you to take a book or magazine article and feed it directly into an electronic computer file. All OCR systems include an optical scanner for reading text, and sophisticated software for analyzing images. Most OCR systems use a combination of hardware and software to recognize characters, although some inexpensive systems do it entirely through software. Advanced OCR systems can read text in large variety of fonts, but they still have difficulty with handwritten text.

 Optical Mark Recognition (OMR)

OMR is also called mark sensing is a technology where an OMR device senses the presence or absence of mark, such as a pencil mark. OMR is used in tests such as aptitude tests.

Bar Code Reader

You are probably familiar with the bar code reader in supermarkets, bookshops, etc. Bar code readers are photo electric scanners that read the bar codes, or vertical zebra striped marks, printed on the product container. Super market use a bar code system called the Universal Product Code (UPC). The bar code identifies the product to the supermarket’s computer, which has a description and the latest price of product.

Speech Input Devices

Speech input devices convert a person’s speech into digital form. These input devices, when combined with appropriate software, form voice recognition system. These systems enable users to operate microcomputer using voice commands.

Touch screen

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

Touch pad

A small touch pad used as a pointing device on some portable computers. Bu moving a finger or other object along the pad, you can move the pointer on the display screen.

Light pen

Light pen is an input device that utilizes a light sensitive detector to select objects on a display screen. A light pen is similar to a mouse, except that with a light pen you move the pointer and select objects on the display screen by directly pointing to the objects with the pen.

 Digital camera

Images can be input into computer using a digital camera. These images can then be manipulated in many ways using the various imaging tools available. The digital camera takes a still photograph, stores it and then sends it as digital input the computer. The images are then stored as digital files.