why the results of this code are same?
<pre><code>static void increment(int num)
{
    num++;
}

static void Main(string[] args)
{   
    int x = 30;
    Console.WriteLine(x);
    increment(x);
    Console.WriteLine(x);
}
</code></pre>

<p>Hi, I am wondering why the result of this code is <strong>30</strong> and <strong>30</strong>, NO ANY CHANGE? thanks!</p>
