Soft key

A softkey or 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 is often located alongside a display device of a portable device such as a cellular phone, where the button invokes a function described by the text at that moment shown adjacent to the button on the display. However, softkeys 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. Softkeys are generally found on keyboards (e.g. the F keys), cellular phones, Automated Teller Machines, Primary Flight and Multi-Function Displays, although they are also found elsewhere. Hard key is the contrary term, which means a hard-coded key such as a number key pad or the Send/End key of a mobile phone. Depending on the development company, cellular phone softkeys are often called F1(Left), F2(Right).

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.

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Wikipedia