% http://tex.stackexchange.com/questions/131546/
\documentclass{article}

\usepackage{xcolor}
\usepackage{listings}
\usepackage[use-files]{xsim}

\lstset{
  frame=single,
  xleftmargin=20pt,
  numbers=left,
  numberstyle=\small,
  tabsize=2,
  breaklines,
  showspaces=false,
  showstringspaces=false,
  language=C,
  basicstyle=\small\ttfamily,
  commentstyle=\itshape\color{gray}
}

\begin{document}

\begin{exercise}[points=6]
Consider the following C program.
\begin{lstlisting}
#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("hello, world\n");
}
\end{lstlisting}
\end{exercise}
\begin{solution}
Consider the following C program.
\begin{lstlisting}
#include <stdio.h>

int main(int argc, char *argv[]) {
  printf("hello, world\n");
}
\end{lstlisting}
\end{solution}

\pagebreak
\printsolutions 

\end{document}