// From https://www.planet-casio.com/Fr/forums/topic14992-1-programmer-en-c-sur-graph-3575-e.html

/* itoa:  convert n to characters in s */
void itoa(int n, char s[])
{
     int i, j, sign;
    char c;

     if ((sign = n) < 0)  /* record sign */
         n = -n;          /* make n positive */
     i = 0;
     do {       /* generate digits in reverse order */
         s[i++] = n % 10 + '0';   /* get next digit */
     } while ((n /= 10) > 0);     /* delete it */
     if (sign < 0)
         s[i++] = '-';
     s[i] = '\0';
     for (i = 0, j = strlen(s)-1; i<j; i++, j--) {
         c = s[i];
         s[i] = s[j];
         s[j] = c;
     }
}