All computer peripheral devices which use to input data and instructions to the computer are called Input Devices. Input devices accept data and instructions from the user and convert information or data into a form that can be understood by the computer.
A good input device should provide accurate, timely, and useful data to the main memory of the computer for processing.
Common Input Devices
Keyboard
Mouse
Light Pen
Trackball
Joystick
Scanners
Optical Mark Reader
Optical Character Reader
Barcode Reader
Magnetic Ink Character Recognition
Voice Recognition Systems
Digital Cameras
Keyboard
A computer keyboard is an input device that allows a person to enter letters, numbers, and other symbols (these are called characters) into a computer. It is one of the most used input devices for computers. Using a keyboard to enter lots of data is called typing.
A keyboard contains many mechanical switches or push-buttons called "keys". When one of these is pushed, an electrical circuit is closed, and the keyboard sends a signal to the computer that tells it what letter, number, or symbol it would like to be shown on the screen. The computer's CPU then shows the character on the screen, usually at the place where the cursor is. Besides entering characters, computer keyboards also have keys that change the symbol (such as shift or caps lock) or give the computer special commands (such as the arrow keys, CTRL and ALT). Different computer operating systems use different special keys or use them differently.
Mouse
A computer mouse is a hand-held pointing device that detects two-dimensional motion relative to a surface. This motion is typically translated into the motion of a pointer on a display, which allows a smooth control of the graphical user interface. The first public demonstration of a mouse controlling a computer system was in 1968. Originally wired to a computer, modern mice are often cordless, relying on short-range radio communication with the connected system. Mice originally used a ball rolling on a surface to detect motion, but modern mice often have optical sensors that have no moving parts. In addition to moving a cursor, computer mice have one or more buttons to allow operations such as the selection of a menu item on a display. Mice often also feature other elements, such as touch surfaces and "wheels", which enable additional control and dimensional input.
Light Pen
A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT display.
It allows the user to point to displayed objects or draw on the screen in a similar way to a touch screen but with greater positional accuracy. A light pen can work with any CRT-based display, but its ability to be used with LCDs was unclear (though Toshiba and Hitachi displayed a similar idea at the "Display 2006" show in Japan.
A light pen detects a change of brightness of nearby screen pixels when scanned by a cathode ray tube electron beam and communicates the timing of this event to the computer.
Trackball
A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball to position the on-screen pointer, using their thumb, fingers, or commonly the palm of the hand while using the fingertips to press the mouse buttons.
Compared with a mouse, a trackball has no limits on effective travel; at times, a mouse can reach an edge of its working area while the operator still wishes to move the screen pointer farther. With a trackball, the operator just continues rolling, whereas a mouse would have to be lifted and re-positioned.
Joystick
A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. A joystick, also known as the control column, is the principal control device in the cockpit of many civilian and military aircraft, either as a center stick or side-stick. It often has supplementary switches to control various aspects of the aircraft's flight.
Joysticks are often used to control video games, and usually have one or more push-buttons whose state can also be read by the computer.
Scanner
An image scanner—often abbreviated to just scanner, although the term is ambiguous out of context (barcode scanner, CT scanner, etc.)—is a device that optically scans images, printed text, handwriting or an object and converts it to a digital image. Commonly used in offices are variations of the desktop flatbed scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, have evolved from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming, and other applications.
Modern scanners typically use a charge-coupled device (CCD) or a contact image sensor (CIS) as the image sensor, whereas drum scanners, developed earlier and still used for the highest possible image quality, use a photomultiplier tube (PMT) as the image sensor.
OMR
OMR (optical mark recognition) is a form of automated data input. Marks are made on specially printed paper forms which are then read by an OMR reader. The data is then sent to a computer for processing. One of the most common uses of OMR is in multiple-choice examinations.
OCR
OCR (optical character recognition) is the recognition of printed or written text characters by a computer. This involves photo scanning of the text character-by-character, analysis of the scanned-in image, and then translation of the character image into character codes, such as ASCII, commonly used in the data processing.
Barcode Reader
A barcode reader (or barcode scanner) is an electronic device that can read and output printed barcodes to a computer. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.
MICR
MICR code is a character-recognition technology used mainly by the banking industry to ease the processing and clearance of cheques and other documents. The MICR encoding, called the MICR line, is at the bottom of cheques and other vouchers and typically includes the document-type indicator, bank code, bank account number, cheque number, cheque amount, and a control indicator. The technology allows MICR readers to scan and read the information directly into a data-collection device. Unlike barcodes and similar technologies, MICR characters can be read easily by humans.
Digital Camera
A digital camera, which captures images and transfers the captured images to a host computer, includes an image sensor exposed to image light for capturing the images and generating image signals; an A/D converter for converting the image signals into digitized image data; a digital interface for transferring the digitized image data to the host computer; means for controlling the image sensor in at least two different camera configurations, each configuration including configuration information defining a plurality of camera parameters; and means for communicating at least part of the configuration information along with the digitized image data to the computer via the digital interface.
