What Is an Event in Programming? Definition and Examples

In programming, an event is an action or occurrence that a program can detect and respond to — such as a mouse click, a key press, or the start of a game — which then triggers a specific piece of code to run. Events let a program react to the user and the world instead of following one fixed path from top to bottom.

Programs built this way are called "event-driven." Instead of running every line in order, the code waits, listens for something to happen, and runs the matching instructions only when that event occurs. The code that responds is often called an event handler.

How an Event Works

Every event has two parts: the trigger (what happens) and the handler (the code that runs in response). In Scratch, the block "when green flag clicked" is an event — the moment a child presses the green flag, all the code attached below it starts running. Other Scratch events include "when this sprite clicked" or "when space key pressed." In Python, a game might use pygame.event.get() to check whether the player pressed a key or closed the window. A fun fact: modern apps handle thousands of events every second, from every tap to every scroll.

Why It Matters for Kids

Events are how kids make their projects interactive — a cat that meows when clicked, or a score that rises when a coin is caught. Learning events builds the cause-and-effect thinking that STEM and Malaysia's KSSR curriculum encourage. Young coders can explore events in Algonova coding classes, or first learn what a variable is.

Curious minds can try a free trial lesson and build their first clickable project.