\section{State Machines}
There are 3 types of state machines.
\begin{center}
  \ttfamily
  \begin{tikzpicture}[
      node distance = 3mm,
      box/.style = {
        draw = black, thick, fill = gray!20!white,
        minimum width = 20mm, minimum height = 8mm,
      }
    ]

    % mealey
    \begin{scope}
      \node[box] (G) {\large G};
      \node[box, above = of G] (F) {\large F};
      \node[box, below = of G] (Z) {\large Z};

      \node[above = of F] {\large Mealey};

      \draw[very thick, ->, hsr-blue] (F.east) -- ++(1,0) node[right] {oup};
      \draw[very thick, ->, hsr-lakegreen] (G.east) -- ++(.5,0) |- (Z.east);
      \draw[very thick, ->] (Z.west) -- ++(-.5,0) |- ($(G.west) - (0,.25)$);
      \draw[very thick, ->] (G.west) ++ (-.5,-.25) |- ($(F.west) + (0,.25)$);

      \draw[very thick, ->, hsr-mauve] ($(G.west) + (-1.5,.25)$)
        node[left] {inp} -- ++(1.5,0);
      \draw[very thick, ->, hsr-mauve] ($(G.west) + (-1,.25)$) |- ($(F.west) - (0,.25)$);
    \end{scope}

    % moore
    \begin{scope}[yshift = -42mm]
      \node[box] (G) {\large G};
      \node[box, above = of G] (F) {\large F};
      \node[box, below = of G] (Z) {\large Z};

      \node[above = of F] {\large Moore};

      \draw[very thick, ->, hsr-blue] (F.east) -- ++(1,0) node[right] {oup};
      \draw[very thick, ->, hsr-lakegreen] (G.east) -- ++(.5,0) |- (Z.east);
      \draw[very thick, ->] (Z.west) -- ++(-.5,0) |- ($(G.west) - (0,.25)$);
      \draw[very thick, ->] (G.west) ++ (-.5,-.25) |- (F.west);

      \draw[very thick, ->, hsr-mauve] ($(G.west) + (-1.5,.25)$)
        node[left] {inp} -- ++(1.5,0);
    \end{scope}

    % Medwedjew
    \begin{scope}[yshift = -80mm]
      \node[box] (G) {\large G};
      \node[box, below = of G] (Z) {\large Z};

      \node[above = of G, yshift = 3mm] {\large Medwedjew};

      \draw[very thick, ->, hsr-lakegreen] (G.east) -- ++(.5,0) |- (Z.east);
      \draw[very thick, ->, hsr-blue] (Z.west) -- ++(-.5,0) |- ($(G.west) - (0,.25)$);
      \draw[very thick, ->, hsr-blue] (G.west) ++ (-.5,-.25) |- ($(G.east) + (1,.75)$)
        node[right] {oup};

      \draw[very thick, ->, hsr-mauve] ($(G.west) + (-1.5,.25)$)
        node[left] {inp} -- ++(1.5,0);
    \end{scope}
  \end{tikzpicture}
\end{center}