Answer»
- Normal execution of a programs may be preempted if some device requires urgent SERVICING.
- For example, a monitoring device in a computer-controlled industrial process may detect a dangerous condition. In order to deal with the situation immediately, the normal execution of the current program must be interrupted. To do this, the device raises an interrupt signal.
- An interrupt is a request from an I/O device for SERVICE by the processor. The processor provides the requested service by executing an APPROPRIATE interrupt-service routine. Because such diversions may alter the internal state of the processor, its state must be saved in the memory LOCATIONS before servicing the interrupt.
- Normally, the contents of the PC, the general registers, and some control information are stored in memory.
- When the interrupt service routine is completed, the state of the processor is restored so that the interrupted program may continue.
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