Computer Keyboards and Mice
A computer keyboard is a peripheral computer input device partially modeled after the typewriter keyboard. Physically, a keyboard is an arrangement of rectangular buttons, or keys. A keyboard typically has characters engraved or printed on the keys; in most cases, each press of a key corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. The majority of all keyboard keys produce letters, numbers or signs (characters) that are appropriate for the operator's language. Other keys can produce actions when pressed, and other actions are available by the simultaneous pressing of more than one action key. The mechanisms employed in keyboards essentially involve making an electrical connection when the key is pressed. Keyboards can be connected by a variety of interfaces as well, including PS2, USB, and wireless input devices.
There exist a large number of different arrangements of symbols on keys. These different keyboard layouts arise mainly because different people need easy access to different symbols; typically, this is because they are writing in different languages, but specialized keyboard layouts for mathematics, accounting, and computer programming also exist.
Most of the more common keyboard (input devices) layouts are QWERTY-based and similar, and were designed in the era of the mechanical typewriters, so their ergonomics had to be slightly compromised in order to tackle some of the technical limitations of the typewriters. The letters were attached to levers that needed to move freely; jamming would result if commonly-used letters were placed too close to one another. With the advent of modern electronics, this is no longer an issue. QWERTY layouts and their brethren have been the de facto standard for decades prior to the introduction of the very first computer keyboard, and were primarily adopted for electronic keyboards for this reason. Alternative layouts do exist, the best known of which are the Dvorak and more recently Colemak layouts; however, these are not in widespread use.
There are also other kinds of computer input devices, such as mice, trackballs, tablets, and game controllers (joysticks, gamepads, etc.). Today, a large number of these input devices (from manufacturers like Acecad, Adesso, Genius, Gyration, Kensington, Logitech, Microsoft, Targus, and other) are wireless input devices. And don't forget the mouse pad - the quality and surface texture of your mouse pad has a direct impact on the accuracy and control of your input device.