An event is an occurrence or activity that takes place at a specific time and place. In computer science, an event is an action accepted by a program that is a response to an input from either a user or a program. Events may also refer to changes in status or conditions in a system, where notifications are sent when a particular event has occurred.
Events in software generally involve an action triggered by software, such as events triggered by an external influence. This could be something like a user pressing a button on the screen, for example. To detect external influences, programs often use inputs or monitors. When an event is triggered, a specific code or routine is run.
In computer programming, event handling is a programming paradigm that follows the typical flow of an event-driven application. One of the main purposes of event handling is to register, detect, and respond to external events in meaningful ways. This process is also known as message-driven programming.
Events are also essential in programming environments such as graphical user interfaces (GUIs). An example could be a button on the screen that when clicked, triggers a window to open or a message to be displayed.
To represent events, software usually uses parameters, information, flags, or numbers, stored in variables or data structures. These variables can be updated or queried so that software can process events in real-time.
Event-driven programming is an integral part of most software applications, and plays an important role in the construction of a modern computer system.