The core of codyn exists of a library, libcodyn, which is responsible for parsing and evaluating networks. Using GObject, the library is implemented in C, maintaining an object oriented design while at the same time allowing for easy bindings into other programming languages using gobject introspection.

libcodyn consists of two main parts. The first is the parser, which parses the codyn language and creates a network object accordingly. The parser itself makes use of the public API available in libcodyn so that without loss of generality, networks can be easily manipulated in the same manner as the parser does. Therefore, networks can not only be parsed from file, but can also be entirely constructed dynamically/programmatically.

The second main purpose of libcodyn is to not only construct a network, but also to evaluate it. Internally, libcodyn parses all mathematical expressions into a special purpose byte code representation. A simple, stack based, Virtual Machine in libcodyn then evaluates these byte code instructions and allows for computation of mathematical expressions.