signed or unsigned int in c++ <p>How can i check if given int(or any other data type) is signed or unsigned? I found this function while searching, </p> <pre><code>std::numeric_limits&lt;int&gt;::is_signed </code></pre> <p>But i can only input the data type, is there a way that i can check by variable name, like.</p> <pre><code>signed int x = 5; </code></pre> <p>Now i want to make a function which checks that x is a signed int or not.</p> <p>And if you guys can answer these little questions, that would be highly appreciated.</p> <ol> <li>Why do we use '::' these operators after std? </li> <li>What do they mean when we use them in std::cout, is it the same?</li> <li>Here numeric_limits&lt;> is a class or what?</li> <li>And again, why are we using these '::' before is_signed?</li> </ol>