What is an interrupt?

An interrupt is a signal emitted by a device attached to a computer or from a program within the computer. It requires the operating system (OS) to stop and figure out what to do next. An interrupt temporarily stops or terminates a service or a current process. Most I/O devices have a bus control line called Interrupt Service Routine (ISR) for this purpose. An interrupt signal might be planned (i.e., specifically requested by a program) or it may be unplanned (i.e., caused by an event that may not be related to a program that's currently running on the system).