[Mike Betts]

Adam,

Without getting too detailed, an interrupt is usually a signal to the microprocessor which causes the processor to momentarily halt execution and "call" a subroutine at a specified address.

One of the most popular is a UART (Universal Asynchronous Transmitter/Receiver) for a RS232 communications link. The UART issues an interrupt when it receiver's a character and the interrupt handler takes the character from the UART register and puts it in a queue for use by your program.

After the interrupt handler is finished, it returns to the code where it was interrupted.

Another popular one is a low battery interrupt. The handler saves all your work in temporary files and then initiates a shutdown.

You have interrupts for your hard drive, floppy drive, CDROM, DMA, et cetera. There are also interrupts for a timer to allow multitasking by the operating system.

Interrupts are processed an a priority basis (a higher priority interrupt can interrupt a lower priority).

Hope this short explanation helps.