Define interrupt and Polling


Interrupts

Interrupts are very simple
  • A CPU core can only work with one process at a time, therefore in order to handle multiple tasks the current tasks are stopped in order to process a more important task
  • When the interrupt signal is sent then the CPU pauses its current process and starts handles the interrupt
  • When the task resulting from the interrupt is completed, the CPU resumes with the tasks it was doing before it received the interrupt
  • See hardware and software interrupts on page 6.1.3 Interrupt Register

Polling
  • Polling is the process where the computer waits for an external device to check for it readiness.
  • The computer does not do anything else than check the status of the device
  • Polling is often used with low-level hardware
    • Example: when a printer connected via a Parrnell port the computer waits until the next character has been received by the printer.
    • These process can be as minute as only reading 1 Byte.

Created By: Daniel Gillo, Edited by Jocbe
Last update: 7th January 2011

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