strange output in program

johnmerlino (110)
Most of the below code is pretty simple to follow. Basically it counts the frequency of ascii characters in a file and places the frequencies in an freqarr array, which is the length of ascii character set. The y-axis is the frequency, and when a character has a matching frequency the histogram marks it with an asterisk otherwise blank space. But then it prints the x-axis and I do not understand what's happening in the x-axis:

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#include <stdio.h>

/* NUM_CHARS should really be CHAR_MAX but K&R haven't covered that at this stage in the book */
#define NUM_CHARS 256

int main(void)
{
  int c;
  long freqarr[NUM_CHARS + 1];

  long thisval = 0;
  long maxval = 0;
  int thisidx = 0;

  for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
  {
    freqarr[thisidx] = 0;
  }

  while((c = getchar()) != EOF)
  {
    if(c < NUM_CHARS)
    {
      thisval = ++freqarr[c];
      if(thisval > maxval)
      {
        maxval = thisval;
      }
    }
    else
    {
      thisval = ++freqarr[NUM_CHARS];
      if(thisval > maxval)
      {
        maxval = thisval;
      }
    }
  }

  for(thisval = maxval; thisval > 0; thisval--)
  {
    printf("%4d  |", thisval);
    for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
    {
      if(freqarr[thisidx] >= thisval)
      {
        printf("*");
      }
      else if(freqarr[thisidx] > 0)
      {
        printf(" ");
      }
    }
    printf("\n");
  }
  printf("      +");
  for(thisidx = 0; thisidx <= NUM_CHARS; thisidx++)
  {
    if(freqarr[thisidx] > 0)
    {
      printf("-");
    }
  }
  printf("\n       ");
  for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
  {
    if(freqarr[thisidx] > 0)
    {
      printf("%d", thisidx / 100);
    }
  }
  printf("\n       ");
  for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
  {
    if(freqarr[thisidx] > 0)
    {
      printf("%d", (thisidx - (100 * (thisidx / 100))) / 10 );
    }
  }
  printf("\n       ");
  for(thisidx = 0; thisidx < NUM_CHARS; thisidx++)
  {
    if(freqarr[thisidx] > 0)
    {
      printf("%d", thisidx - (10 * (thisidx / 10)));
    }
  }
  if(freqarr[NUM_CHARS] > 0)
  {
    printf(">%d\n", NUM_CHARS);
  }

  printf("\n");

  return 0;
}


Now here are results of the program that I ran from my own computer:

touch input3.txt
echo "aabbccddeeffgghhiijjkkllmmnopqrstuvwxyz" > input3.txt
gcc -o histogram2 histogram2.c //this is a c program with the above code
cat input3.txt | ./histogram2
2 | *************
1 |***************************
+---------------------------
000011111111111111111111111
199900000000001111111111222
078901234567890123456789012


I really don't understand what all those 0s and 1s are doing there. I assume that the x-axis would contain actual characters of the alphabet.

The code was taken from here:
http://users.powernet.co.uk/eton/kandr2/krx114.html
norm b (337)
Those are ASCII character codes. Things don't line up very well vertically.

010 line feed - count 1 (the asterisk)
097 lower case a - count 2
098 lower case b - count 2
and so on.

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