Why does the program do this? C++
<p>So I have the code</p>

<pre><code>#include &lt;iostream&gt;
using namespace::std;
int main() {
    int a = 1;
    int b = 1;
    while (a &lt; 100) {
        a = a + b; 
        b = a + b;
        cout &lt;&lt; a &lt;&lt; endl;
        cout &lt;&lt; b &lt;&lt; endl;
    }
}
</code></pre>

<p>What it does is print the fibonacci sequence up to 100. But, when I make "a" bigger, say, (OVER 9000!!!) 10 billion, it just prints out random numbers it seems. Why does it do this?</p>
