title: Undefined reference to main - collect2: ld returned 1 exit status
body: <p>I'm trying to compile a program (called es3), but, when I write from terminal:</p>
  
  <p><code>gcc es3.c -o es3</code></p>
  
  <p>it appears this message:</p>
  
  <pre><code>/usr/lib/gcc/i686-linux-gnu/4.4.5/../../../../lib/crt1.o: In function `_start':
  (.text+0x18): undefined reference to `main'
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>What could I do?</p>