Code for Converting Hexadecimal File to ASCII File

#include <stdio.h>
int  main(int argc, char * argv[])
{
  int n, count;
  FILE * fpi, *fpo;
  if (argc != 3)
  {
    fprintf(stderr, "usage %s <binary_filename> <ascii_filenam>\n", argv[0]);
    return -1;
  }
  fpi = fopen(argv[1], "rb");
  if (!fpi)
  {
    printf("unable to open file %s\n", argv[1]); 
    return -2;
  }
  fpo = fopen(argv[2], "w");
  if (!fpo)
  {
    printf("unable to open file %s\n", argv[2]); 
    fclose(fpi);
    return -3;
  }
  count=0;
  while ( (n=fgetc(fpi)) != EOF)
  {
    int i;
    for (i=0; i<2; i++)
    {    
      unsigned char b = (n & 0xF0) >> 4;
      if ( b < 10 )
        fputc(b + '0', fpo);
      else 
        fputc(b-10 + 'A', fpo);
      n <<= 4;
    }
    count++;
    // optional...
    if (!(count % 16)) 
      fputc('\n', fpo); 
    else
      fputc(' ', fpo);
  }
  fclose(fpo);
  fclose(fpi);
  return 0;
}