About `disassemble'

[Xue Fuqiao]

I have a question about `disassemble' in Emacs Lisp:

     (defun silly-loop (n)
       "Return time before and after N iterations of a loop."
       (let ((t1 (current-time-string)))
         (while (> (setq n (1- n))
                   0))
         (list t1 (current-time-string))))
          => silly-loop
     
     (disassemble 'silly-loop)
     =>
     byte code for silly-loop:
       doc:  Return time before and after N iterations of a loop.
       args: (n)
     0       constant  current-time-string
     1       call      0
     2       varbind   t1
     3:1     varref    n
     4       sub1      
     5       dup       
     6       varset    n
     7       constant  0
     8       gtr       
     9       goto-if-not-nil 1
     12      varref    t1
     13      constant  current-time-string
     14      call      0
     15      unbind    1
     16      list2     
     17      return    

What does the number at the left side mean (i.e. 0, 1, 2, 3:1, ... ,
17)?  It isn't explained in the Emacs Lisp manual.  Can anybody help?
Thanks.

-- 
Best regards, Xue Fuqiao.
http://www.emacswiki.org/emacs/XueFuqiao