Event-driven programming

In computer programming, event-driven programming is a programming paradigm in which the flow of the program is determined by external events. User interface (UI) events from keyboards and mice, touchpads and touchscreens, and external sensor inputs are common cases. Events may also be programmatically generated, such as from messages from other programs, notifications from other threads, or other network events. Event-driven programming is the dominant paradigm used in graphical user interface (GUI) applications and network servers. In an event-driven application, there is generally an event loop that listens for events and then triggers a callback function when one of those events is detected. Event-driven programs can be written in any programming language, although the task is easier in languages that provide high-level abstractions. Although they do not exactly fit the event-driven model, interrupt handling and exception handling have many similarities. It is important to differentiate between event-driven and message-driven (aka queue-driven) paradigms: event-driven services (e.g. AWS SNS) are decoupled from their consumers, whereas message/queue-driven services (e.g. AWS SQS) are coupled with their consumers.