title: I can’t use sprintf()
body: <p>I want to cast <code>int</code> to <code>char</code>.
  This is my code.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  int main(){
          int i = 7;
          char *s;
          sprintf(s,"sprint f = %d",i);
          printf("printf s = [%s]",s); 
  } 
  </code></pre>
  
  <p>It ends <code>Segmentation fault</code>.
  What’s wrong is it?</p>