How to create step by step annotated programming tutorial in LaTeX?

Question

(question inspired by How to create a crossword puzzle in LaTeX? and provided solutions)

How to make in most comfortable way in LaTeX (I use pdfLaTeX, but I am open for LuaTeX solutions) annotated, step by step, programming tutorials? Preferably from annotated sourcecode? Or in other way, by less effort than typing each slide by slide.

I means questions and answers tutorial in form of presentation (I don't know if beamer is the only solution for presentations, but I've heard it's popular one).

Here is an example how such presentation would look like:

*-------------------------------------------*
|      How to implement Main function?      |
|                                           |
|                                           |
| (1)?                                      |
|                                           |
|                                           |
|                                           |
|                                           |
|    (2)?                                   |
| (1)                                       |
|                                           |
| (1) ... ?                                 |
| (2) ... ?                                 |
*-------------------------------------------*

*-------------------------------------------*
|              Main function                |
|                                           |
|                                           |
| int main(){ (1)                           |
|                                           |
|                                           |
|                                           |
|                                           |
|    return 0; (2)                          |
| } (1)                                     |
|                                           |
| (1) ...                                   |
| (2) ...                                   |
*-------------------------------------------*

*-------------------------------------------*
|        How to perform Computation?        |
|                                           |
|                                           |
| int main(){                               |
|    (3)?                                   |
|                                           |
|    (4)?                                   |
|                                           |
|    return 0;                              |
| }                                         |
|                                           |
| (3) ...?                                  |
| (4) ...?                                  |
*-------------------------------------------*

*-------------------------------------------*
|              Computation                  |
|                                           |
|                                           |
| int main(){                               |
|    long a,b,c; (3)                        |
|                                           |
|    c = a * b; (4)                         |
|                                           |
|    return 0;                              |
| }                                         |
|                                           |
| (3) ...                                   |
| (4) ...                                   |
*-------------------------------------------*

*-------------------------------------------*
|            Input & Output  ?              |
|                                           |
| (5) ?                                     |
| int main(){                               |
|    long a,b,c;                            |
|    (6) ?                                  |
|    c = a * b;                             |
|    (6) ?                                  |
|    return 0;                              |
| }                                         |
|                                           |
| (5) ...?                                  |
| (6) ...?                                  |
*-------------------------------------------*

*-------------------------------------------*
|            Input & Output                 |
|                                           |
| #include <cstdio> (5)                     |
| int main(){                               |
|    long a,b,c;                            |
|    scanf("%ld%ld", &a, &b); (6)           |
|    c = a * b;                             |
|    printf("%ld\n", c); (6)                |
|    return 0;                              |
| }                                         |
|                                           |
| (5) ...                                   |
| (6) ...                                   |
*-------------------------------------------*

Answer 1

An interactive version with beamer may be constructed along the following lines:

\documentclass{beamer}

\begin{document}

\begin{frame}[fragile]%
\begin{semiverbatim}
\frametitle{Input \&\ Output}
\#include <cstdio>
\only<1>{(1)?}\only<2->{int main() \{}
   \only<3>{(3)?}\only<4->{long a,b,c;}
   \only<4>{(4)?}\only<5->{std::scanf("\%ld\%ld", \&a, \&b);}
   \only<5>{(5)?}\only<6->{c = a * b;}
   \only<6>{(6)?}\only<7->{std::printf("\%ld\textbackslash n", c);}
   \only<2>{(2)?}\only<3->{return 0;}
 \}
\end{semiverbatim}
\end{frame}

\end{document}