The Free On-line Dictionary of Computing (30 December 2018):
1. An asynchronous event that suspends normal
processing and temporarily diverts the flow of control
through an "interrupt handler" routine.
Interrupts may be caused by both hardware (I/O, timer,
machine check) and software (supervisor, system call or
In general the computer responds to an interrupt by storing
the information about the current state of the running
program; storing information to identify the source of the
interrupt; and invoking a first-level interrupt handler.
This is usually a kernel level privileged process that can
discover the precise cause of the interrupt (e.g. if several
devices share one interrupt) and what must be done to keep
operating system tables (such as the process table) updated.
This first-level handler may then call another handler,
e.g. one associated with the particular device which generated
2. Under MS-DOS, nearly synonymous with "system call"
because the OS and BIOS routines are both called using the
INT instruction (see interrupt list) and because programmers
so often have to bypass the operating system (going directly
to a BIOS interrupt) to get reasonable performance.