An operating system also has to be able to service peripheral (71), such as timers,motors, sensors, communication devices, disks, etc. All of those can request the attention of the OS (72) , i.e. at the time that they want to use the OS, the OS has to make sure it's ready to service the requests. Such a request for attention is called an interrupt. There are :wo kinds of interrupts: Hardware interrupts and Software interrupts. The result of an inteiTup: is also a triggering of the processor, so that it jumps to a (73) address. Examples of cases where software interrupts appear are perhaps a divide by zero, a memory segmentation fault, etc. So this kind of interrupt is not caused by a hardware event but by a specific machine language operation code. Many systems have more than one hardware interrupt line, and the hardware manufacturer typically assembles all these interrupt lines in an interrupt (74) . An Interrupt (75) is a piece of hardware that shields the OS from the electronic details of the interrupt lines, so that interrupts can be queued and none of them gets lost.
