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.