% 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, fill=gray!50](b){$p_1$};
    \node at (b.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](c){$p_2$};
    \node at (c.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](d){\texttt{a}};
    
    \node at (a.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](e){$p_3$};
    \node at (e.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](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, fill=gray!50](h){\texttt{d}};

    \node at (e.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](i){$p_4$};
    \node at (i.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](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, fill=gray!50](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, fill=gray!50](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, fill=gray!50](p){\texttt{k}};

    %%%%%%%%

    \node at (3.0,0) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](aa){\texttt{}};
    \node at (aa.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](bb){$p_1$};
    \node at (bb.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](cc){$p_2$};
    \node at (cc.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](dd){\texttt{a}};
    %
    \node at (aa.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](ee){$p_3$};
    \node at (ee.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](ff){\texttt{b}};
    \node at (ff.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](gg){\texttt{c}};
    \node at (gg.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](hh){\texttt{d}};

    \node at (ee.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](ii){$p_4$};
    \node at (ii.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](jj){\texttt{e}};
    \node at (jj.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](kk){\texttt{f}};
    \node at (kk.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](ll){\texttt{g}};

    \node at (ii.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](mm){\texttt{h}};
    \node at (mm.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](nn){\texttt{i}};
    \node at (nn.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](oo){\texttt{j}};
    \node at (oo.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](pp){\texttt{k}};

    %%%%%%%%

    \node at (6.0,0) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](aaa){\texttt{}};
    \node at (aaa.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](bbb){$p_1$};
    \node at (bbb.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](ccc){$p_2$};
    \node at (ccc.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](ddd){\texttt{a}};
    %
    \node at (aaa.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](eee){$p_3$};
    \node at (eee.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](fff){\texttt{b}};
    \node at (fff.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](ggg){\texttt{c}};
    \node at (ggg.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](hhh){\texttt{d}};

    \node at (eee.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](iii){$p_4$};
    \node at (iii.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](jjj){\texttt{e}};
    \node at (jjj.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](kkk){\texttt{f}};
    \node at (kkk.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](lll){\texttt{g}};

    \node at (iii.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](mmm){\texttt{h}};
    \node at (mmm.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](nnn){\texttt{i}};
    \node at (nnn.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](ooo){\texttt{j}};
    \node at (ooo.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](ppp){\texttt{k}};

    %%%%%%%%

    \node at (9.0,0) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](aaaa){\texttt{}};
    \node at (aaaa.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](bbbb){$p_1$};
    \node at (bbbb.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](cccc){$p_2$};
    \node at (cccc.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](dddd){\texttt{a}};
    %
    \node at (aaaa.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm](eeee){$p_3$};
    \node at (eeee.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](ffff){\texttt{b}};
    \node at (ffff.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](gggg){\texttt{c}};
    \node at (gggg.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm](hhhh){\texttt{d}};

    \node at (eeee.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](iiii){$p_4$};
    \node at (iiii.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](jjjj){\texttt{e}};
    \node at (jjjj.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](kkkk){\texttt{f}};
    \node at (kkkk.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](llll){\texttt{g}};

    \node at (iiii.south) [rectangle, draw, anchor=north, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](mmmm){\texttt{h}};
    \node at (mmmm.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](nnnn){\texttt{i}};
    \node at (nnnn.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](oooo){\texttt{j}};
    \node at (oooo.east) [rectangle, draw, anchor=west, minimum height=0.6cm, minimum width=0.6cm, fill=gray!50](pppp){\texttt{k}};
\end{tikzpicture}