Source code presentation

[Zhongtao Zhu]

Hello all,

I want to get source codes presented in line step by step, either from
head to tail, like a cascade, or in a sequence of pre-defined sort.
For instance, the program below

====================================================
      line     source
     number     code
----------------------------------------------------
        0   #include <stdio.h>
        1
        2   int main()
        3   {
        4           printf("Hello, world...\n");
        5   }
----------------------------------------------------

is expected to be able to display in a buffer in sequence of
        0 1 2 3 4 5
or
        2 3 4 0 1 5
once a line by pressing some key, say [F7], for each; and get the
displaced codes disappear in the reverse order once a line when
pressing other key, say [F8]. 

I think of this functionality would be extremely helpful for students
to understand the creating procedure of programming. BTW: I teach. :-)

Is there a elisp package for this has been existed? 

Responses are eagerly expected and a lot of thanks,
-- 
Zhongtao Zhu                          Tel: +86 10 6278 2266
Department of Computer, Tsinghua University, Beijing, China