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interrupt
Last modified: Tuesday, January 27, 2004
(n.) A signal informing a program that an event has occurred. When a program receives an interrupt signal, it takes a specified action (which can be to ignore the signal). Interrupt signals can cause a program to suspend itself temporarily to service the interrupt.
Interrupt signals can come from a variety of sources. For example, every keystroke generates an interrupt signal. Interrupts can also be generated by other devices, such as a printer, to indicate that some event has occurred. These are called hardware interrupts. Interrupt signals initiated by programs are called software interrupts. A software interrupt is also called a trap or an exception.
PCs support 256 types of software interrupts and 15 hardware interrupts. Each type of software interrupt is associated with an interrupt handler -- a routine that takes control when the interrupt occurs. For example, when you press a key on your keyboard, this triggers a specific interrupt handler. The complete list of interrupts and associated interrupt handlers is stored in a table called the interrupt vector table, which resides in the first 1 K of addressable memory.
Interrupt Function and Operation Detailed description of hardware interrupts from "The PC Guide". Contains separate sections on interrupt controllers, IRQ lines, interrupt priority, interrupt conflicts, and Non-Maskable Interrupts (NMI).
Interrupt list Contains a listing of interrupt calls, I/O ports, memory locations, and far-call interfaces for IBM PCs and compatible machines.
