History
Keyboard layouts have evolved over time. The earliest mechanical keyboards were used in musical instruments to play particular notes. With the advent of printing telegraph, a keyboard was needed to select characters. Some of the earliest printing telegraph machines used a layout similar to a piano keyboard.
In countries using the Latin script, the center, alphanumeric portion of the modern keyboard is most often based on the QWERTY design by Christopher Sholes, who laid out the keys in such a way that common two-letter combinations were placed on opposite sides of the keyboard so that his mechanical keyboard would not jam, and laid out the keys in rows offset horizontally from each other by three-eighths, three-sixteenths, and three-eighths inches to provide room for the levers. Although it has been demonstrated that the QWERTY layout is not the most efficient layout for typing, it has become such a standard that people will not change to a more efficient alphanumeric layout.
Sholes chose the size of the keys to be on three-quarter inch (0.75-inch) centers (about 19 mm, versus musical piano keys which are 23.5 mm or about 0.93 inches wide). Actually, 0.75 inches has turned out to be optimum for fast key entry by the average size hand, and keyboards with this key size are called “full-sized keyboards”.
The standard 101/102-key PC keyboard layout was invented by Mark Tiddens of Key Tronic Corporation in 1982. IBM adopted the layout on its PC AT in 1984 (after previously using an 84-key keyboard which did not have separate cursor and numeric key pads).
Most modern keyboards basically conform to the layout specifications contained in parts 1, 2, and 5 of the international standard series ISO/IEC 9995. These specifications were first defined by the user group at AFNOR in 1984 working under the direction of Alain Souloumiac. Based on this work, a well known ergonomic expert wrote a report which was adopted at the ISO Berlin meeting in 1985 and became the reference for keyboard layouts.
The 104/105-key PC keyboard was born when two ⊞ Win keys and a ≣ Menu key were added on the bottom row (originally for the Microsoft Windows operating system). Newer keyboards may incorporate even further additions, such as Internet access (World Wide Web navigation) keys and multimedia (access to media players) buttons.
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