itoa:convert integer to characters.

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

     if((sign = n) < 0) /* record sign */
          n = -n;      /* make n positive */
     i = 0;  
     do {
        s[i++] = n % 10 + '0'; /* get next digit */
     } while ((n /= 10) > 0);   /*delete it */
     if (sign < 0)
         s[i++] = '-';
     s[i] = '\0';
     reverse(s);
}