Composer of Electronic and Chamber Music, Freelance Programmer

This document will (hopefully) serve as an easy to read and understand introduction to the process of writing an external for Pure Data. Pure Data, or PD, is a visual programming environment designed for real-time computer music applications. PD is open-source software, under the BSD license, and expansion of the software in the form of externals is strongly encouraged.

PD and its externals are written in the C programming language. When PD is running an external, it makes no distinction between the ‘core’ functionality and the external code. There are hundreds of user-written externals freely available for use and study. As you learn to write externals yourself, I strongly encourage studying other people’s code. For example, I learned about timing issues from studying the “pipe” object.

To get started coding an external, you’ll need a text editor. I use Textwrangler, but there are a few good, free editors out there. Get one with syntax highlighting. You’ll also need to install GCC, the Gnu C Compiler, and Make. If you’re on OS X, you can just install Apple’s XCode Developer Tools, and you’ll have both of these programs installed. I’m going to assume some knowledge of using the command line here, so I won’t explain how to use GCC or run Make. (Hint: type “make”.) You’ll also need an installation of PD, so that you can link and run your externals.

In the next post, I’ll talk about the basic concepts and chunks of code that you’ll need to write your external.