Inline documentation for source files should follow the Doxygen formatting conventions.

Non-documentation comments are strongly encouraged. A general rule of thumb is that if you look at a section of code and think "Wow, I don't want to try and describe that", you need to comment it before you forget how it works.

Non-documentation comments should use capitalized sentences with punctuation. Sentences should be separated by single spaces. All caps are used in comments only when referencing constants, for example TRUE. Comments should be on a separate line immediately before the code line or block they reference. For example:

// Unselect all other contact categories.
db_query('UPDATE {contact} SET selected = 0');

If each line of a list needs a separate comment, the comments may be given on the same line and may be formatted to a uniform indent for readability.

C style comments (/* */) and standard C++ comments (//) are both fine. Use of Perl/shell style comments (#) is discouraged.