A soft key is a programmable button that performs various functions rather than a fixed one, often found alongside a display device with a label indicating its current function. These keys appear on devices like cellular phones for actions such as PTT or volume control. Unlike hard keys with dedicated functions, soft keys adapt depending on context. Screen-labeled function keys are common in kiosks such as ATMs and gas pumps, and have roots in aviation displays like the primary flight and multi-function displays. While touchscreens are increasingly replacing soft keys, screen-labeled keys remain valued for their durability and tactile feedback.
History
Early examples are found in aviation glass cockpits, such as the Mark II avionics of the F-111D in the late 1960s/early 1970s (first ordered 1967, delivered 1970–73). Hewlett-Packard 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 Amigo, which used keys at the right side of the screen and HP 250 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
As of 2008, 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 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. 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 systems; NCR Corporation claims that their DynaKey system "has been proven to reduce training time and cashier errors".1
- 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
- Media related to Soft key at Wikimedia Commons
References
"NCR RealPOS™ DynaKey". NCR Corporation. http://www.ncr.com/retail/food-drug-mass-merchandise/assisted-service-hardware/realpos-peripherals/ncr-realpos-dynakey ↩