Display devices
A display device is an output device that visually conveys text, graphics, and video information. Information shown on a display device is called soft copy because the information exists electronically and is displayed for a temporary period of time. Display devices include CRT monitors, LCD monitors and displays, gas plasma monitors, and televisions.[3]
Input/output
There are many input and output devices such as mprinters and computer-based navigation systems that are used for specialised or unique applications.[1] In computing,input/output, or I/O, refers to the communication between an information processing system(such as a computer), and the outside world. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it.
Types of output
Some types of output are text, graphics, tactile[4], audio, and video. Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring one byte of computer storage space) that are used to create words, sentences, and paragraphs. Graphics are digital representations of nontext information such as drawings, charts, photographs, and animation (a series of still images in rapid sequence that gives the illusion of motion). Tactile output such as raised line drawings may be useful for some individuals who are blind. Audio is music, speech, or any other sound. Video consists of images played back at speeds to provide the appearance of full motion.[3]
Graphics
A digital image is a numeric representation of an image stored on a computer. They don't have any physical size until they are displayed on a screen or printed on paper. Until that point, they are just a collection of numbers on the computer's hard drive that describe the individual elements of a picture and how they are arranged.[5] Some computers come with built-in graphics capability. Others need a device, called a graphics card or graphics adapter board, that has to be added.[6] Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.[7] Depending on whether the image resolution is fixed, it may be of vector or raster type. Without qualifications, the term "digital image" usually refers to raster images also called bitmap images. Raster images that are composed of pixels and is suited for photo-realistic images. Vector images which are composed of lines and co-ordinates rather than dots and is more suited to line art, graphs or fonts. [5] To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color.[7]
Tactile
Haptic technology, or haptics, is a tactile feedback technology which takes advantage of the sense of touch by applying forces, vibrations, or motions to the user.[8] Several printers and wax jet printers have the capability of producing raised line drawings. There are also handheld devices that use an array of vibrating pins to present a tactile outline of the characters or text under the viewing window of the device.[4]
Audio
Speech output systems can be used to read screen text to computer users. Special software programs called screen readers attempt to identify and interpret what is being displayed on the screen[9] and speech synthesizers convert data to vocalized sounds or text.[6]
