A temporary suspension of a process. In PC computers interrupts are used to suspend one activity in order to give priority to another more important activity. Interrupt signals, also known as Interrupt Requests (IRQ) are identifiable by a unique number and can have varying levels of priority, but in general they all cause the OS to stop what it is doing and decide what to do next. They can come from software or hardware devices. Many things you do on a regular basis, such as pressing a key on your keyboard or clicking your mouse generate an interrupt that causes the computer to take some action based on how it is programmed to handle that particular interrupt. MIDI and other music related hardware connected to PC computers generally need to have unique IRQ identities in order for communication between the computer and the hardware to take place properly. To that end there are methods for choosing the ID on most hardware that is to be connected to a PC. A similar analogy would be SCSI devices, where each one has to have a unique ID number. PC computers have routines known as Interrupt Handlers and Interrupt Schedulers that enable them to manage the regular flow of I/O for the system and keep everything running smoothly and on time.