One of the major problems that software library writers face, particularly in a research environment, is the generation of documentation. Producing good, professional-quality documentation is tedious and time consuming. Often, no documentation is produced. For many users, however, much of the need for documentation may be satisfied by a brief description of the purpose and use of the routines and their arguments. Even for more complete, hand-generated documentation, this information provides a convenient starting point. We describe here a tool that may be used to generate documentation about programs written in the C language. It uses a structured comment convention that preserves the original C source code and does not require any additional files. The markup language is designed to be an almost invisible structured comment in the C source code, retaining readability in the original source. Documentation in a form suitable for the Unix man program (nroff), LaTeX, and the World Wide Web can be produced.