Create control flow graph using tikz?

Question

I am trying to integrate a nice looking control flow graph for an algorithm in one of my papers:

static void PrintEven(int x)
{
    int c = 0;
    while (c <= x)
    {
        if (c % 2 == 0)
            Console.WriteLine(c);
        c++;
    }
    Console.WriteLine("Done.");
}

I first did create the cfg with http://www.webgraphviz.com/ which looked horrible:

I was told to create the graph with tikz instead to make it look better. I was told this is the go to way to implement CFGs in a paper. By nice looking I mean a nice vertical structure, the entry node to be at the top and the exit node (The Console.WriteLine("Done")) at the bottom. Also if the arrows would not be rounded but instead look somewhat like in this picture that would be nice:

Can someone tell me how I can create a CFG for my algorithm with tikz?

Answer 1

This is not necessarily an answer but an attempt to steer the above discussion into a different direction. Flowchart type diagrams are abundant on this site. A nice example is given in this answer, a slight variation of which I add here. (Note that I am not a programmer, so it is quite possible that I use the wrong styles for the elements of that flow chart. This is an additional reason to make this a community wiki.)

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{positioning}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}[node distance=1cm,font=\sffamily,
    startstop/.style={rectangle, rounded corners, minimum width=3cm, minimum height=1cm,text centered, draw=black, fill=red!30},
    process/.style={rectangle, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=orange!30},
    io/.style={trapezium, trapezium left angle=70, trapezium right angle=110, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=blue!30},
    decision/.style={diamond, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=green!30},
    arr/.style={very thick,-latex}
    ]
    \node (int) [startstop]                             {\texttt{int c=0;}};
    \node (while) [process,below=of int]  {\texttt{while (c <= x)}};
    \draw[arr] (int) -- (while);
    \node (if) [decision,below=of while]        {\texttt{if (c \% 2 == 0)}};       
    \draw[arr] (while) -- (if);
    \node (write) [process,right=of if] {\texttt{Console.WriteLine(c);}};
    \draw[arr] (if) -- (write) node[midway,above]{yes};
    \node (pp) [process,below=of if]  {\texttt{c++;}};
    \draw[arr] (if) -- (pp) node[midway,left]{no};
    \draw[arr] (write) |- (pp);
    \draw[arr] (pp.west) -- ++ (-1,0) |- (while) node[pos=0.25,left]{$c\le x$};
\end{tikzpicture}
\end{document}

Here I also have "an alternative"... (... it seems that "alternative" means one copies from another post without mentioning it, keeps 90% and makes some small changes here and there. OK, this is an "alternative", then, ;-)

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{positioning,shapes.geometric}
\begin{document}
\begin{tikzpicture}[node distance = 9mm and 14mm,
    nodes= {draw, minimum width=8em, minimum height=2em,
                    font=\ttfamily},
startstop/.style = {fill=red!30, rounded corners},
  process/.style = {fill=orange!30},
       io/.style = {fill=blue!30,
                    trapezium, trapezium stretches body,
                    trapezium left angle=70, trapezium right angle=110},
 decision/.style = {fill=green!30, diamond, aspect=1.5},
 exp/.style={draw=none,font=\sffamily,minimum width=1em},
      arr/.style = {very thick,-latex}
    ]
\node (int) [io]    {int c=0;};
\node (while) [process,below=of int]    {while (c <= x)};
\draw[arr] (int) -- (while);
\node (if) [decision,below=of while]    {if (c \% 2 == 0)};
\draw[arr] (while) --  node[exp,right]  {$c\le x$} (if);
\node (write)   [process,below=of if]   {Console.WriteLine(c);};
\draw[arr] (if) --  (write) node[exp,pos=0.5,left] {yes};
\node (pp)      [process,below=of write]    {c++;};
\draw[arr] (write) -- (pp);
\draw[arr] (if.east)  --  ++ (1,0) node[exp,pos=0.5,above] {no} |- (pp) ;
\node (done)   [startstop,below right=of write]   {Console.WriteLine("Done");};
\draw[arr] (while) -| (done)   node[exp,pos=0.25,above] {$c> x$};
\draw[arr] (pp.west) -- ++ (-1,0) |- (while);
\end{tikzpicture}
\end{document}

Answer 2

An alternative solution based on my one old answer to the similar question. Compare to it the MWE below try to replicate your first image in your question:

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{positioning,
                shapes.geometric}

\begin{document}
    \begin{tikzpicture}[
   node distance = 8mm and 12mm,
     base/.style = {draw, fill=#1,
                    minimum width=28mm, minimum height=7mm,
                    font=\ttfamily},
startstop/.style = {base=red!30, rounded corners},
  process/.style = {base=orange!30},
       io/.style = {base=blue!30,
                    trapezium, trapezium stretches body,
                    trapezium left angle=70, trapezium right angle=110},
 decision/.style = {base=green!30, diamond, aspect=1.5},
      arr/.style = {semithick,-latex}
    ]
\node (int) [io]    {int c=0;};
\node (while) [process,below=of int]    {while (c <= x)};
    \draw[arr] (int) -- (while);
\node (if) [decision,below=of while]    {if (c \% 2 == 0)};
    \draw[arr] (while) --  node[right]  {$c\le x$} (if);
\node (write)   [process,below=of if]   {Console.WriteLine(c);};
    \draw[arr] (if) -- node[left] {yes} (write);
\node (pp)      [process,below=of write]    {c++;};
    \draw[arr] (write) -- (pp);
    \draw[arr] (if.east)  -- node[above] {no} ++ (1,0) |- (pp);
\node (done)   [startstop,
                below right=of write]   {Console.WriteLine("Done");};
    \draw[arr] (while) -| (done)   node[pos=0.25,above] {$c> x$};
    \draw[arr] (pp.west) -- ++ (-1,0) |- (while);
\end{tikzpicture}
\end{document}