Open Babel is a library for bioinformatics, chemistry, materials science, and solid-state physics. It focuses on the interconversion of a variety of molecular-based file formats, although there are many features above and beyond this main task.
This tutorial is aimed at developers looking to use Open Babel as a library. It will focus on the object-oriented application programmers' interface (API). There is also documentation on the full API. Although Open Babel is written in C++, it also has wrappers to Perl and Python programming languages. Consequently, some examples in this tutorial will be written in C++, Perl, and Python to give examples in different programming language syntax.
This document is very much a "work in progress." If you find it useful or have suggestions or concerns, please e-mail  with your feedback.