#include <stdio.h>

void die_read(void)
{
  fprintf(stderr,"file3: fatal: unable to read data.txt\n");
  exit(111);
}

int main(void)
{
  FILE *f;
  char c;

  f = fopen("data.txt","r");
  if (!f) die_read();

  while (fscanf(f,"%c",&c) == 1)
    printf("data.txt has the byte %d, which is printed as \"%c\".\n",c,c);
  if (ferror(f)) die_read();

  return 0;
}