A keyboard is an arrangement of buttons or keys that act as mechanical levers or electronic switches to input data into computers. Despite the development of alternative input devices, the keyboard is still the most commonly used and most versatile device used for direct input into computers.

A keyboard typically has letters, numbers, and signs printed on the keys. Each press of a key normally corresponds to a single written symbol. However, producing some symbols requires pressing and holding several keys at the same time or in a sequence. For regular usage, the keyboard allows text and numbers to be typed directly into a word processor or other similar program. In a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard differentiates between keys and reports all key presses to the controlling software.

There are several different types of keyboards available. Standard alphanumeric keyboards have keys that are on three-quarter inch centers and have a keystroke of at least 0.150 inches. Desktop computer keyboards contain alphabetic characters, punctuation symbols, numbers, and many other function keys. Keyboards on laptops and notebook computers usually have a shorter travel distance for the keystroke and a reduced number of keys. Also, the keys may be in different places. Numeric keyboards contain only numbers and mathematical symbols for addition, subtraction, multiplication, and division, along with some function keys. They are often used to ease data entry with smaller keyboards that do not have a numeric keypad. Chorded keyboards, unlike most keyboards that associate one action with each key, associate actions with combinations of key presses. Since there are many combinations available, chorded keyboards can efficiently generate more actions on a board with less keys. There are also software, foldable, projection, and optical keyboards, all of which are other types of keyboards.

The layout of a keyboard is very important. The Dvorak Simplified Keyboard layout arranges keys so that frequently used keys are easiest to press, which reduces muscle fatigue when typing common English. However, there are a number of different arrangements of alphabetic, numeric, and punctuation symbols on keys. The reason there are different keyboard layouts is mainly because different people need easy access to different symbols. This can be due to text being inputted in different languages or simply because they need a specialized layout for accounting, computer programming, or other purposes. Christopher Sholes invented the QWERTY layout to reduce the likelihood of jamming when letter-keys were attached to levers that needed to move freely. The QWERTY layouts are now widely used, while alternative layouts such as the Dvorak Simplified Keyboard are not.

To assist users, keyboards can also be equipped with things such as modifiers, which modify the normal action of another key, and navigation keys, such as arrow keys and tab keys. Furthermore, keyboards may be illuminated from inside, especially on equipment for mobile use, to help users who are working in darker environments.

In the early 1970s, the first electronic keyboards came out with key switches that were individual switches inserted into holes in metal frames. Soon after, however, lower-cost direct-contact key switches were introduced. The down side was that their life in switch cycles was much shorter because they were open to the environment. As time went on, this became more acceptable for use in computer terminals. Key Tronic Corporation introduced keyboards with capacitive-based switches in 1978. The design was simple: a sponge pad with a conductive-coated plastic sheet on the switch plunger, and two crescent trace patterns on the printed circuit board beneath it. When the key was pressed, the capacitance between the plunger pad and the patterns on the PCB below changed. Key Tronic quickly became the largest independent keyboard manufacturer. Meanwhile, IBM made their own keyboards with a different design: keys on older IBM keyboards were made with a mechanism that had a coil spring under the key buckles that was put under pressure by the user’s finger. This in turn pressed a rubber dome, completed a circuit, and made a clicking sound.

Some drawbacks came along with keyboards. Keystroke hacking is a method of capturing and recording user keystrokes. At times this can be helpful, however it is also used by hackers for various illegal or spiteful acts. Due to this problem becoming widespread, manufacturers are constantly designing new software that detects and prevents this from happening. Another problem is physical injury. Using any keyboard regularly may cause serious injury to hands, wrists, arms, neck or back, such as carpal tunnel syndrome. Such injuries can be prevented by taking frequent breaks and using proper posture when sitting at a keyboard.

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