A key press is a press and release of a key (down and up).
Typically, the primary action of the key is performed when the key is pressed down, already before the key is released (there may be exceptions to this rule; see Typical functions of the standard keys for an example).
Some functions depend on the length of the key press:
In a short press, the key is held down for less than 0.6 seconds (please note that this time-out value may depend on the product implementation). If the key is held down longer, the result is a long key press.
If the pressed key (in the given context) has functions for both a short and long press, the short key press action is performed first at the moment when the key is pressed down. If the key press is long, then the long key press action is performed. In the case of the Home / Menu key and the Edit key, the interaction is different, causing the action on the key release event.
Certain keys, possibly in certain contexts only, may perform key repeat. Key repeat starts after the long key press time-out when the key is continuously being held down, and the associated function is performed according to the key repeat frequency. For example, in scrolling within lists and text editors, these frequencies are by default 6 times/second for vertical and 10 times/second for horizontal scrolling (the repeat frequency may be product or application specific).
Long key press actions and key repeat actions are not defined at the same time; only one can occur in the given context.
The primary key press action should not be conflicting with the long key press action or key repeat action.
Note: With certain input hardware (for example, Roller), long key presses and key repeat may not be possible. The long key press actions and key repeat actions should be designed so that this does not cause harm: the long key press must never be the only way to perform a function.