title: undefined reference in cs50 week 1 course
body: <p>I am enrolled in CS50. I am working on the week 1 project. #include  at the top of the program is supposed to have certain programs already defined, such as get_string, get_int, etc... Before I get into the project I ran a simple test to make sure everything was working.</p>
  
  <pre><code>#include &lt;cs50.h&gt;
  #include &lt;stdio.h&gt;
  
  int main(void)
      {
          printf("What is your name?\n");
          string x = get_string("x");
          printf("Hello, %x!");
      }  
  </code></pre>
  
  <p>My code is above and below is the error I keep receiving.</p>
  
  <pre><code>undefined reference to `get_string'
  clang-7: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>Aren't those errors already referenced when I put in #include ?</p>