What is the primary purpose of an event handler in programming?

The primary purpose of an event handler in programming is to trigger functions in response to asynchronous events. This means that when a specific action occurs, such as a user clicking a button, moving a mouse, or receiving data from a server, the event handler is designed to respond to that action by executing a predefined block of code. This interaction is crucial in building dynamic applications that react to user input or other external events, allowing developers to create a more engaging and interactive user experience.

In the context of event-driven programming, the event handler serves as a crucial link between the occurrence of an event and the application's subsequent behavior, effectively enabling the program to react in real-time to user interactions or system changes.