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.
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.