Anything from ‘ /* ’ through the next ‘ */ ’ is a comment. This means you may not nest these comments.
/* The only way to include a newline ('\n') in a comment is to use this sort of comment. */ /* This sort of comment does not nest. */
Anything from a line comment character up to the next newline is considered a comment and is ignored. The line comment character is target specific, and some targets multiple comment characters. Some targets also have line comment characters that only work if they are the first character on a line. Some targets use a sequence of two characters to introduce a line comment. Some targets can also change their line comment characters depending upon command-line options that have been used. For more details see the Syntax section in the documentation for individual targets.
If the line comment character is the hash sign (‘ # ’) then it still has the special ability to enable and disable preprocessing (see Preprocessing ) and to specify logical line numbers:
To be compatible with past assemblers, lines that begin with ‘ # ’ have a special interpretation. Following the ‘ # ’ should be an absolute expression (see Expressions ): the logical line number of the next line. Then a string (see Strings ) is allowed: if present it is a new logical file name. The rest of the line, if any, should be whitespace.
If the first non-whitespace characters on the line are not numeric, the line is ignored. (Just like a comment.)
# This is an ordinary comment. # 42-6 "new_file_name" # New logical file name # This is logical line # 36.
This feature is deprecated, and may disappear from future versions of as .