Keyboard. In addition to letters and numbers found on a typewriter, computer keyboards have a series of special keys to control sending information to the CPU. The use of these special keys is defined and controlled by the software. For example, with word processing software, arrow keys move the cursor to any point in a document.
Mouse. A mouse is an input device that operates by controlling the position of the cursor (in the shape of an arrow) on the monitor.
Light pen. Light pens, often used in stores, are able to input a large amount of data quickly by moving a light beam across a barcode. This converts the bar- code into digital data that is usable by the computer. Other types of light pens are also used for computer-aided design (CAD) and pen-based computers; the latter interpret and convert human writing into computer form.
Scanner. A scanner is an input device that acts like a miniature photocopy machine connected to a computer, copying graphic images into the computer and allowing typewritten pages to be entered without retyping. Scanners include both hand-held and desktop models. A scanner works by passing a beam of light across the original page or artwork and sensing the reflected light; it then assembles this information into a data file that describes the images as rows of tiny dots, each one noted for its colour and brightness. That file is then passed on to the computer.
