title: Why printf("%.1f", 1) output 0.0
body: <p>I use the <em>codeblock</em>.</p>
  
  <p>when the code is:</p>
  
  <pre><code>printf("%.1f", 1);
  </code></pre>
  
  <p>The program can run,and the output is <code>0.0</code>. I want to know why.
  `</p>