A soft key is a button flexibly programmable to invoke any of a number of functions rather than being associated with a single fixed function or a fixed set of functions. A softkey often takes the form of a screen-labeled function key located alongside a

display device A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...

, where the button invokes a function described by the text at that moment shown adjacent to the button on the display. Soft keys are also found away from the display device, for example on the sides of cellular phones, where they are typically programmed to invoke functions such as PTT, memo, or volume control. Function keys on

keyboards Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...

are a form of soft key. In contrast, a hard key is a key with dedicated function such as the keys on a number keypad. Screen-labeled function keys are today most commonly found in kiosk applications, such as automated teller machines and gas pumps. Screen-label function keys date to aviation applications in the late 1960s. Kiosk applications were particularly common in the 1990s and 2000s. Screen-labeled function keys are found in automotive and aviation applications such as in the primary flight and multi-function displays. An alternative to screen-labeled function keys is buttons (virtual keys) on a touchscreen, where the label is directly pushable. The increased prevalence of touchscreens in the 2000s has led to a decrease in screen-labeled function keys. However, screen-labeled function keys are inexpensive and robust, and provide tactile feedback.

History

Early examples are found in aviation

glass cockpit A glass cockpit is an aircraft cockpit that features electronic (digital) flight instrument displays, typically large LCD screens, rather than the traditional style of analog dials and gauges. While a traditional cockpit relies on numerous mech ...

s, such as the Mark II avionics of the

F-111D The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production variants of the F-111 had roles that included ground attack (e.g. interdiction), strategic bombing (including nuclear weapons cap ...

in the late 1960s/early 1970s (first ordered 1967, delivered 1970–73).

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

developed them for use in computers/calculators in the 1970s. The HP 9830 desktop computer was the first calculator with two rows of 4 keys, over which a paper overlay would be placed. These were later adapted to terminals. Programmers found that the HP 2640 terminals could lock the top two lines of the screen, so they displayed the key functions there. Starting with HP 2647 terminal, the keys were re-arranged to correspond with 2 pairs of 4 labels at the bottom of the screen. These could be programmed by escape sequence or configuration screen. This would be further developed on the failed

HP 300 HP may refer to: Businesses and organisations * HP Inc., an American technology company ** Hewlett-Packard, the predecessor to HP Inc. * HP Foods ** HP Sauce, formerly made by HP Foods * Handley Page, an aircraft company * Hindustan Petroleum * ...

Amigo, which used keys at the right side of the screen and

HP 250 The HP 250 was a multiuser business computer by Hewlett-Packard running HP 250 BASIC language as its OS with access to HP's IMAGE database management. It was produced by the General Systems Division (GSD), but was a major repackaging of deskt ...

business computers which placed them at the bottom. By arranging functions in hierarchical trees, many functions can be implemented with only 8 keys.

Graphical calculators

, HP calculators use this arrangement to implement hierarchical trees of functions. They are rarely found on PC applications, even though the first IBM PC BASIC labeled function key use at the bottom of the screen, and there were 12 function keys, patterned after use on IBM terminals. Modern Texas Instruments calculators such as the

TI-89 series The TI-89 and the TI-89 Titanium are graphing calculators developed by Texas Instruments (TI). They are differentiated from most other TI graphing calculators by their computer algebra system, which allows symbolic manipulation of algeb ...

use function keys to open drop-down menus on their menu bar, the menu title acting like the key label. Casio calculators use the function keys for a menu at the bottom of the screen.

Mobile phone

A typical mobile phone with soft keys has them located beneath the bottom left and bottom right of the display; some, especially those made by Nokia, have an additional center soft key, activated by pressing on the center of the

directional pad A D-pad (short for directional pad or digital pad; officially referred to by Nintendo as a +Control Pad) is a flat, usually thumb-operated, often digital, four-way directional control with one button on each point, found on nearly all modern vid ...

. Depending on the modality of the application, various functions can be mapped onto it. It can also bring up multiple functions listed on a pop-up expanded menu. Usually the prompt text on the display for the softkey is not allowed to be truncated or omitted with ellipsis. The softkey itself is usually not printed with a functional icon or text, but is often marked with a dot or short bar. Soft keys have become increasingly rare as touchscreens take the place of function keys on many modern smartphones.

Point of sale

Screen-labeled function keys have found use in

point of sale The point of sale (POS) or point of purchase (POP) is the time and place at which a retail transaction is completed. At the point of sale, the merchant calculates the amount owed by the customer, indicates that amount, may prepare an invoice f ...

systems;

NCR Corporation NCR Corporation, previously known as National Cash Register, is an American software, consulting and technology company providing several professional services and electronic products. It manufactures self-service kiosks, point-of-sale termin ...

claims that their ''DynaKey'' system "has been proven to reduce training time and cashier errors".

References

*Kiljander, Harri (2004) “Evolution and usability of mobile phone interaction styles” Helsinki University of Technology, dissertation *Lindholm, Christian. Keinonen, Turkka, Kiljander, Harri (2003) “Mobile usability : how Nokia changed the face of the mobile phone” New York : McGraw-Hill

External links

*{{Commonscatinline Input/output Graphical user interface elements