Which language uses .pde extension?

file-extension, processing

Solution

This code is from Processing.org an open source Java based IDE. You can find it Processing.org. The Arduino IDE also uses this extension, although they run on a hardware board.

EDIT - And yes it is C syntax, used mostly for art or live media presentations.

Problem

While searching for an implementation of the Barnsley's Fern fractal I came across a implementation that has .pde extension. Which programming language uses this extension? Implementation Page

Original source