Code

 Header...
#define HSFILE "highscore.txt"
//
// Read the high score from a file, returning zero
// if the file does not exist.
 int readhighscore(){
   ... 

»  int hs;
»  FILE *infile;

»  infile=fopen(HSFILE, "r");
»  if (infile==NULL) // First time game has been played
    return 0;

»  fscanf(infile, "%d", &hs);

»  fclose(infile);

»  return hs;
}

//
// Write the high score file checking that this game's
// high score is greater than the saved one.
 void writehighscore(int hs){
   ... 

»  FILE *outfile;
  
»  if (hs<=readhighscore()) 
    return ;

»  outfile=fopen(HSFILE, "w");
»  if (outfile==NULL) {
»    fprintf(stderr, "Cannot write high-score file\n");
»    exit(1);
  }

»  fprintf(outfile, "%d", hs);

»  fclose(outfile);
}

 int main(){
   ... 

»  int highscore;

»  highscore=readhighscore();
»  printf("High score: %d\n", highscore);

»  writehighscore(12);
»  highscore=readhighscore();
»  printf("High score: %d\n", highscore);
  
»  writehighscore(2);// Will do nothing
»  return 0;
}

Data