Keyboard layouts

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The terms "QWERTY" and "QWERTY keyboard" that are used to describe a typewriter or computer keyboard or its layout refer to the arrangement of the letters on the keys. The QWERTY layout dates from 1874, created for the Sholes and Glidden Type-Writer from Remington. QWERTY was created at the same time that typewriters entered the mass-market in the 19th century. Prior to this, typewriter keyboards had been arranged alphabetically and in several competing non-alphabetic layouts.

The QWERTY layout is significant because, despite many changes to the layouts of keyboards in well over a hundred years, it has remained steadfastly unchanged on commercial keyboards. Not all keyboards are strictly QWERTY however. French keyboards are "AZERTY", with Q and A swapped and W and Z swapped. Likewise, German keyboards are "QWERTZ", with Y and Z swapped.

Incidentally, limitations of Sholes and Glidden's typewriter mechanism is the cause of rows being offset relative to one-another, known as staggering.

Physical layout

The physical layout of keyboard is the size, shape and position of all the keys on a keyboard. Historically, there was no standard way to lay out a terminal or computer keyboards, neither by manufacturer nor by product. Beyond the position of the letter keys (in QWERTY layout), and typically the number keys in a row above, key arrangement was specific to each piece of equipment or model of keyboard.

Following the creation of the clone market based around the IBM Personal Computer, the keyboard layouts used on IBM PCs were adopted by other manufacturers and became de-facto standards. Modern keyboards are based on the physical layout of the IBM Enhanced Keyboard, commonly known as the "IBM Model M" (it is part of the IBM Model M family). IBM and DEC terminal keyboard layouts also became de-facto standards.

The basic arrangement of keys depends primarily on country. In Japan, the requirements for text input led to keyboards with a total of four more keys than standard US keyboards, while keyboards in most European countries have one more key.

By necessity laptop keyboards have fewer keys, and the reduction in size of the layout is not standardised. Desktop computer keyboards also see variation in layout.

Logical layout

In the early days of computing, many so-called "ASCII keyboards" contained circuitry that told the host computer which character was typed using ASCII. Such keyboards did not need to care what type of computer they were attached to, and computers did not need to care what type of keyboard the owner had purchased. This was typical with kit-based computers where the keyboard had to be bought separately and where there was no authorised keyboard supplier.

Modern keyboards instead transmit a numeric code indicating the position of the key on a the keyboard. These codes are called scancodes. The computer is free to interpret these codes however it wishes, although certain keys are treated specially by the keyboard controller circuitry within the keyboard, such as the modifier keys under the USB protocol, or by the hardware (in particular alternate action keys).

Due to the differing requirements of languages around the world, the keys on a keyboard are assigned different characters in for each country. The legends—the letters, numbers and symbols printed on the keys—are country and language specific, but the scancodes sent by the computer are independent of what's printed in the keys. The computer interprets each scancode according to the logical layout selected on the computer, which is why operating system installers ask for or verify your choice of input language. The input language cannot be determined from the keyboard itself.

Typically the computer will also permit selecting between multiple layouts on the fly, either from a pull-down menu or a keyboard shortcut. This allows people to type in different languages using the same keyboard, by swapping between different input languages. Self-adhesive labels with alternative legends assist with using the same keyboard for more than one language.

Changing keyboard layout

For how to change layout in an environment, see the page for each such environment:

Keyboard size

In addition to full-size keyboards, there are a number of smaller sizes:

  • Tenkeyless — no numeric keypad
  • 75% — variants of this layout are found on laptops but also on desktop keyboards
  • 60% — a smaller layout still, comprising only the area from left control up to backspace on a standard keyboard; there are no function keys or cursor keys
  • 40% — smaller still, with no number row; commercial 40% keyboards are rare

Alternative layouts

In addition to standard layouts (both logical and physical), there are also many custom layouts, typically designed for the purposes of improving typing efficiency.

See also

External links