How to write documentation comments in ANSI C?

There are many different standards, if you want to generate documentation, try doxygen

You can use javadoc standard and then use doxygen that understands javadoc to generate a documentation.

In doxygen I recommend using the option JAVADOC_AUTOBRIEF set to YES. If the JAVADOC_AUTOBRIEF tag is set to YES then doxygen will interpret the first line (until the first dot) of a Javadoc-style comment as the brief description.

Example for a class definition:

/**
 * A brief description. A more elaborate class description
 * @param bool somebool a boolean argument.
 * @see Test()
 * @return The test results
 */

(Some more examples in the doxygen manual)

Installation is really simple, there is a GUI and a nice graphical visualisation available with:

apt-get install doxygen doxygen-gui graphviz

Run the gui calling doxywizard and use the Wizard settings, only JAVADOC_AUTOBRIEF has to be set there in "Expert" settings.