% Author: Prof. Dr. Matthias Jung, DL9MJ
% Year: 2023
\begin{tikzpicture}
    \node at (0,0)    [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](a){\texttt{}};
    \node at (a.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](b){\texttt{}};
    \node at (b.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](c){\texttt{}};
    \node at (c.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](d){\texttt{a}};
    %
    \node at (a.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](e){\texttt{}};
    \node at (e.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](f){\texttt{b}};
    \node at (f.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](g){\texttt{c}};
    \node at (g.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](h){\texttt{d}};

    \node at (e.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](i){\texttt{}};
    \node at (i.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](j){\texttt{e}};
    \node at (j.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](k){\texttt{f}};
    \node at (k.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](l){\texttt{g}};

    \node at (i.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](m){\texttt{h}};
    \node at (m.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](n){\texttt{i}};
    \node at (n.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](o){\texttt{j}};
    \node at (o.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](p){\texttt{k}};
\end{tikzpicture}