title: C programming check digit
body: <pre><code>bool print_date(Date *d, char **argv) {
  
          if (isdigit(*argv+1)) {
                  return printf("is d");
          } else {
                  return printf("is not d");
          }
  
  }
  </code></pre>
  
  <p>The above function don't work. *argv+1 is the user input, is it a string or what types when passing in? anyone can help?</p>
  
  <pre><code> int main(int argc, char *argv[])
   {
  
    Date d;
  
    get_date(&amp;d, argv);
  
  
   }
  </code></pre>