Input Devicesz

Graphic Input Devices Input Device Keyboard

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Description

The set of typewriter-like keys that enables you to enter data into a computer. Computer keyboards are similar to electrictypewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows: 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 a QWERTY keyboard.

Mouse

A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard, flat surface. Its name is derived from its shape, which looks a 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 contain at least one button and sometimes as many as three, which have different functions depending on what program is running. Some newer mice also include a scroll wheel for scrolling through long documents.

Trackball

A pointing device. It is trackball is a mouse lying on its back. To move the pointer, you rotate the ball with your thumb, your fingers, or the palm of your hand. There are usually one to three buttons next to the ball, which you use just like mouse buttons Joystick

A lever that moves in all directions and controls the movement of a pointer or some other display symbol. A joystick is similar to a mouse, except that with a mouse the 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 occasionally for CAD/CAM systems and other applications. Touch screen

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, you can use your finger to point directly to objects on the screen. Graphics tablet

An input device that enables you to enter drawings and sketches into a computer. A digitizing tablet consists of an electronic tablet and a cursor or pen. Numeric keypad

It contains the digits from 0 to 9, arithmetic operation keys, enter key to input numbers instantaneously .It is generally attached to keyboard.

Scanner

Devices that can read text or illustrations printed on paper and translate the information into a form the computer can use. A scanner works by digitizing an image -- dividing it into a grid of boxes and representing each box with either a zero or a one, depending on whether the box is filled in. (For colour and grey scaling, the same principle applies, but each box is then represented by up to 24 bits.) The resulting matrix of bits, called a bit map, can then be stored in a file, displayed on a screen, and manipulated by programs.

Graphic Output Devices

CRT

LCD

Dual monitors

CAD

Abbreviation of cathode-ray tube, the technology used in most televisions and computer display screens. A CRT works by moving an electron beam back and forth across the back of the screen. Each time the beam makes a pass across the screen, it lights up phosphor dots on the inside of the glass tube, thereby illuminating the active portions of the screen. By drawing many such lines from the top to the bottom of the screen, it creates an entire screen of images. A monitor that uses LCD technologies rather than the conventional CRT technologies used by most desktop monitors. Until recently, LCD panels were used exclusively on notebook computers and other portable devices. In 1997, however, several manufacturers began offering full-size LCD monitors as alternatives to CRT monitors. The main advantage of LCD displays is that they take up less desk space and are lighter. Currently, however, they are also much more expensive. A computer system with more than one display connected. Dual monitor systems consist of adding additional video adapters (also called video cards) to it, or by using a single video card that has multiple ports for monitors (called a dual head card). The second display screen can be any display, such as a television, projector, or monitor. Also called a multi-monitor Acronym for computer-aided design. A CAD system is a combination of hardware and software that enables engineers and architects to design everything from furniture to airplanes. In addition to the software, CAD systems require a highquality graphics monitor; a mouse, light pen, or digitizing tablet for drawing; and

a special printer or plotter for printing design specifications

Video Adaptor

Printer

A board that plugs into a personal computer to give it display capabilities. The display capabilities of a computer, however, depend on both the logical circuitry (provided in the video adapter) and the display monitor. A monochrome monitor, for example, cannot display colours no matter how powerful the video adapter

A device that prints text or illustrations on paper. There are many different types of printers. In terms of the technology utilized, printers fall into the following categories: Daisy-wheel: Similar to a ball-head typewriter, this type of printer has a plastic or metal wheel on which the shape of each character stands out in relief. A hammer presses the wheel against a ribbon, which in turn makes an ink stain in the shape of the character on the paper. Daisy-wheel printers produce letter-quality print but cannot print graphics. Dot-matrix: Creates characters by striking pins against an ink ribbon. Each pin makes a dot, and combinations of dots form characters and illustrations. Ink-jet: Sprays ink at a sheet of paper. Ink-jet printers produce highquality text and graphics. Laser: Uses the same technology as copy machines. Laser printers produce very high quality text and graphics. LCD & LED : Similar to a laser printer, but uses liquid crystals or light-emitting diodes rather than a laser to produce an image on the drum. Line printer: Contains a chain of characters or pins that print an entire line at one time. Line printers are very fast, but produce low-quality print. Thermal printer: An inexpensive printer that works by pushing heated pins against heat-sensitive paper. Thermal printers are widely used in calculators and fax machines.

Speakers

Plotters

An electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance. Synonymous with loudspeaker

A device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolour plotters use different-colour pens to draw different colours. In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.