In
computer science, the
event loop,
message dispatcher,
message loop,
message pump, or
run loop is a programming construct that waits for and dispatches
events or
messages in a
program. It works by making a request to some internal or external "event provider" (that generally
blocks the request until an event has arrived), and then it calls the relevant
event handler ("dispatches the event"). The event-loop may be used in conjunction with a
reactor, if the event provider follows the file interface, which can be selected or 'polled' (the Unix system call, not actual
polling). The event loop almost always operates asynchronously with the message originator.