void main( void )
{
   unsigned char checksum;
   int x;

   char nema_string[] = "$GPRMC,000004,V,3714.6284,N,12146.9181,W,0.000,0.0,290697,15.4,E*4C";
   printf( " %s\n", nema_string );
   checksum = nema_string[0];

   for( x = 3; x < strlen(nema_string)-3; ++x )
   {
      checksum ^= nema_string[x];
   }

   printf( " NEMA Checksum is %02X\n", checksum );

}