"这种算法 怎么实现  ？"

I use a custom itoa to do that.

==============================
void ultoa(unsigned char *str, unsigned long ul, unsigned char length) {
  do {
    str[length--]=(ul % 10) + '0';
    ul = ul / 10;
  } while (ul);  //eliminates leading zeros
  //} while (length);  //keeps leading zeros
}

==============================

so a the following

ultoa (&vRAM[3], 123, 10);

will create a string of '       123', starting at vRAM[3]. no trailing null, however.