title: Specific name of # (hash) as in preprocessor directives like #include, #define, etc
body: <p>What does it exactly convey?
  Also, it is used in USSD codes in phones. Do they mean the same thing?
  Is there any particular name/group for the symbol '#'?For example !, ||, &amp;&amp; belong to logical operators, &gt;, &lt;, ==, etc., belong to relational operators.</p>