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copied!<ol> <li>The <code>&</code> operator, like the <code>*</code> operator<sup>1</sup> can be used for two different things depending on whether it's used as a <em>binary</em> or <em>unary</em> operator. <ol> <li>Unary <code>&</code> like <code>&var</code> takes the address of <code>var</code>. This is necessary to pass it to <code>scanf</code>.</li> <li>Binary <code>&</code> like <code>var & var</code> is a bitwise AND, like item #2. <ul> <li>Notice that the spacing doesn't matter. What does matter is if there's operands on both sides of the <code>&</code>. So <code>& var</code> is still unary <code>&</code> and <code>var &var</code> is still binary <code>&</code>.</li> </ul></li> </ol></li> <li><code>(x&x-1)</code> is doing a bitwise AND with <code>x</code> and <code>x-1</code>.</li> <li><code>(x|x-1)</code> is doing a bitwise OR with <code>x</code> and <code>x-1</code>.</li> <li>Yes <code>%</code> means modulus.</li> <li><code>1 << n</code> is doing a bitwise shift of 1 to the left <code>n</code> digits</li> <li>the <code>%i</code> you are seeing as the first argument to <code>printf</code> are format symbols to which specify that the next argument is an <code>int</code>, so that <code>printf</code> can print it properly (because it doesn't know what type it is by itself, so you have to tell it). It has nothing to do with modulus. You can see a very in-depth definition of <code>printf</code> here: <a href="http://pubs.opengroup.org/onlinepubs/9699919799/" rel="nofollow">http://pubs.opengroup.org/onlinepubs/9699919799/</a> (thanks pmg) <ul> <li>If <code>%i</code> were outside a string, it would be to the left of some other operand, and mean modulus.</li> <li><code>%i</code> in a string doesn't mean anything by itself. It only means something to <code>printf</code> because <code>printf</code> treats it specially. It searches the string it gets for occurrences of <code>%format</code> (where <code>format</code> is a format, not the word "format") and does something depending on what format it encounters.</li> </ul></li> </ol> <p><sup>1</sup> The <code>*</code> operator also has two different versions: a unary version and a binary version. The unary version means pointer indirection, and the binary version means multiplication.</p>

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