# Functions & Modularity

**Track:** Foundations — Creative Coding — the existing 50
**Framework / surface:** p5.js
**Level:** Beginner
**Prerequisites:** Loops, Animation & the Frame Loop

**In one line:** Name a behaviour once, reuse it everywhere.

## Theory, aesthetics & inspiration

A function gives a name to a behavior so it can be invoked again without restatement. This is procedural abstraction — the structured-programming discipline Edsger Dijkstra and his contemporaries argued made large programs comprehensible — and it carries an aesthetic as much as an engineering virtue. To define "draw one tree" and call it across a forest is to work the way Sol LeWitt's wall-drawing instructions do: author the procedure once, let assistants or machines execute it many times and places. John Maeda's "Design By Numbers" prized this compression. A good function names a unit of intent at the right altitude, letting the artist think in gestures rather than in individual lines.