title: What does if (! variable_name) mean in c language
body: <p>Here is the problem</p>
  
  <pre><code>int main() {
      int pid = fork();
      if (!pid) {
          // condition 1
      } else {
          // condition 2
      }
      return 0;
  }
  </code></pre>
  
  <p>What does <code>(!pid)</code> do? </p>