9.27.3.1 Special Characters

The characters ‘*’ and ‘#’ are line comment characters; each start a comment at the beginning of a line, but only at the beginning of a line. A ‘#’ prefixes a hexadecimal number if found elsewhere on a line. If a ‘#’ appears at the start of a line the whole line is treated as a comment, but the line can also act as a logical line number directive (see Comments) or a preprocessor control command (see Preprocessing).

Two other characters, ‘%’ and ‘!’, each start a comment anywhere on the line. Thus you can’t use the ‘modulus’ and ‘not’ operators in expressions normally associated with these two characters.

A ‘;’ is a line separator, treated as a new-line, so separate instructions can be specified on a single line.