Which language uses .pde extension?
Solution 1:
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.
Solution 2:
The .pde file extension is the one used by the Processing, Wiring, and the Arduino IDE.
Processing is not C-based but rather Java-based and with a syntax derived from Java. It is a Java framework that can be used as a Java library. It includes a default IDE that uses .pde extension. Just wanted to rectify @kersny's answer.
Wiring is a microcontroller that uses the same IDE. Arduino uses a modified version, but also with .pde. The OpenProcessing page where you found it is a website to exhibit some Processing work.
If you know Java, it should be fairly easy to convert the Processing code to Java AWT.
Solution 3:
Bad news I'm afraid (or maybe great news?) : it isn't C code, it's an example of "Processing" - an open source language aimed at programming images. Take a look here
Looks very cool.
Solution 4:
pde is extesion for:
Processing: Java derived language
Wiring: C/C++ derived language (Wiring is derived from Processing)
Early versions of Arduino: C/C++ derived (Arduino IDE is derived from Wiring)
For Arduino for example the IDE preprocessor is adding some #defines and some C/C++ files before giving all to gcc.