Which term refers to a signal generated by input devices indicating that an event has occurred?

The term that accurately describes a signal generated by input devices to indicate that an event has occurred is "interrupt." In computer science, an interrupt is a signal to the processor emitted by hardware or software indicating an event that needs immediate attention.

When an input device, such as a keyboard or mouse, generates an interrupt, it informs the CPU that it should pause its current operations and process the event associated with that signal. This mechanism allows computers to respond promptly to user inputs or other important events without constantly checking for their occurrence, thus improving efficiency.

The other options do not specifically convey the technical definition synonymous with the behavior of input devices signaling the processor. While 'signal,' 'notification,' and 'alert' can describe related concepts, they lack the specific implication of the immediate action required by the CPU in response to an event, which is central to the definition of an interrupt.