title: Why does this code contain case 0 and default?
body: <p>I don't understand why the switch statement contains <code>case 0:</code> and <code>default:</code>?</p>
  
  <pre><code>int main(void)
  {
      pid_t pid = create_process();
      switch (pid)
      {
          case -1:
              perror("fork");
              return EXIT_FAILURE;
              break;
          case 0:
              child_process();
              break;
          default:
              father_process(pid);
              break;
      }
      return EXIT_SUCCESS;
  }
  </code></pre>