identifier not found error on function call

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int _tmain(int argc, _TCHAR* argv[])
{
    /*Example for fgets*/
    fgetsDemo();

    return 0;
}

void fgetsDemo()
{
FILE *stream;
   char line[100];

   if( fopen_s(&stream, "c:\crt_fgets.txt", "r" ) == 0 )
   {
      if( fgets( line, 100, stream ) == NULL)
         printf( "fgets error\n" );
      else
         printf( "%s", line);
      fclose( stream );
   }
}

void fgetsDemo();
int _tmain(int argc, _TCHAR* argv[])
{
    /*Example for fgets*/
    fgetsDemo();

    return 0;
}