pycdep is a tool for analyzing and visualizing C/C++ header file dependencies. A script extracts information about your code and dumps it in a Prolog database, which is used to query the dependency graph. It comes with a large number of predefined queries for finding out which files include or depend on which other files, how files depend on another file, circular dependencies, transitively implied dependencies, and design rule checks (limitations on which project can include from which other project). Visualization is supported by dumping graphs to .dot files. It also has the beginnings of a natural language interface.