title: CodeBlocks doesn't let me create a project with multiple code files
body: <p>I am very new to coding, so forgive me if my question is too stupid.</p>
  <p>I just started learning how to code in C++ and now I am trying to learn how to create projects with multiple files but there's a problem. When I create a new file, I can't add more files to that project in the left panel in CodeBlocks.</p>
  <p>Also when creating the file, CodeBlocks doesn't let me tick the option &quot;Add file to active procejts In build target(s):&quot;. I am thinking maybe this causes the problem?</p>
  <pre><code>#include &lt;iostream&gt;
  
  int add(int x, int y);
  
  int main()
  {
      std::cout &lt;&lt; &quot;The sum of 3 and 4 is: &quot; &lt;&lt; add(3, 4) &lt;&lt; '\n';
      return 0;
  }
  </code></pre>
  <p>Above is my main file, I want this code to call the below function which should be in the separate file, but it doesn't work.</p>
  <pre><code>int add(int x, int y)
  {
      return x + y;
  }
  </code></pre>
  <p>Thanks very much in advance for all the help!</p>