The system software translates hardware interrupts from

various input devices into messages according to the current

input context (e.g. the active window of the frontmost

application). Each message is a short piece of information.

A message's format depends on its type, which is usually

encoded in its first field. The message is sent to the

client application using some communication protocol

(e.g. shared memory, internal socket, network socket).

The client application dispatches the message and performs any

actions required. The messages can also be sent by client

applications. This provides convenient and flexible

inter-process communication.