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An interrupt is a signal from a peripheral or software program that causes the operating system to stop processing its current list of instructions. This will attract the attention of the processor, this will occur for example when a process or instruction causes an error to occur, for example if your printer is out of paper or if a program has crashed.

An interrupt would also be generated when the user presses a key or moves the mouse.

The operating system is responsible for detecting the interrupt signal and performing the necessary tasks or displaying the appropriate messages. Multi-tasking is only possible because the processor can be interrupted in this way.


  1. current processor state saved on stack
  2. Source of interrupt identified
  3. Appropriate interrupt service routine called
  4. processor state restored