title: what is function for calculating the total length of characters in C++
body: <p>I have question about function that calculate the total length of characters in C++. I found this function :</p>
  
  <pre><code>len = strlen(str1);
  </code></pre>
  
  <p>However, when I tried it in Xcode, Xcode gave me a yellow triangle which indicate something wrong or missing. see the picture below </p>
  
  <p><img src="https://i.stack.imgur.com/yW7cu.png" alt="enter image description here"></p>
  
  <p>So, could anyone help me to find the appropriate function for calculate total length ?</p>