title: Why is my file pointer causing an undefined symbol error?
body: <p>This is my code so far:</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  
  int main(void)
  {
      char filename[50];   /* for holding file's name  */
      FILE *fp;            /* fp is the "file pointer" */
  
      printf("Please enter the name of an input file: ");
      scanf("%s", filename);
  
      if (!(fp = fopen(filename, "w")))    /*w=write*/
              fprintf(stderr, "unable to open file\a\n");
      else {/* process file */
              fprintf(fp, "Testing...\n");
      }
      return 0;
  }
  </code></pre>
  
  <p>The line </p>
  
  <pre><code>FILE *fp; 
  //is giving me an error Undefined Symbol "FILE"
  </code></pre>
  
  <p>The line </p>
  
  <pre><code>fprintf(stderr, "unable to open file\a\n"); 
  //is giving me an error Undefined Symbol "stderr"
  </code></pre>
  
  <p>I thought these keywords were standard C/C++? Why are they giving me errors? </p>