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char* itoa(int num, char* str, int base)
{
    int i = 0;
    bool isNegative = false;
 
    /* Handle 0 explicitely, otherwise empty string is printed for 0 */
    if (num == 0)
    {
        str[i++] = '0';
        str[i] = '\0';
        return str;
    }
 
    // In standard itoa(), negative numbers are handled only with
    // base 10. Otherwise numbers are considered unsigned.
    if (num < 0 && base == 10)
    {
        isNegative = true;
        num = -num;
    }
 
    // Process individual digits
    while (num != 0)
    {
        int rem = num % base;
        str[i++] = (rem > 9)? (rem-10) + 'a' : rem + '0';
        num = num/base;
    }
 
    // If number is negative, append '-'
    if (isNegative)
        str[i++] = '-';
 
    str[i] = '\0'; // Append string terminator
 
    // Reverse the string
    reverse(str, i);
 
    return str;
}

#include <stdio.h>
#include <math.h>

static unsigned char score0[7]={"0000100"};
static unsigned char score1[7]={"0000000"};

static unsigned char i;
static unsigned char a;

/**
 * Add score0 to score1
 */
void add_points(void)
{
  a=0; // clear carry

  // Convert result to binary.
  for (i=6;i-->0; )
    {
      score0[i]=score0[i]-'0';
      score1[i]=score1[i]-'0';
    }

  // Add each piece
  for (i=6;i-->0; )
    {
      score1[i]=score0[i]+score1[i]+a;
      a=(score1[i]>9);
      if (a)
        score1[i]-=10;
    }

  // Convert result back to ASCII
  for (i=6;i-->0; )
    {
      score0[i]=score0[i]+'0';
      score1[i]=score1[i]+'0';
    }
}

void main(void)
{
  for (int q=0;q<1000;++q)
    {
      add_points();
      printf("%c%c%c%c%c%c%c\n",score1[0],score1[1],score1[2],score1[3],score1[4],score1[5],score1[6]);
    }
}