Tikz diagram with stacks and box

Question

I'm trying to make the diagram

in Tikz. I can draw the stacks by adapting this example and the box. But how can I put the description around the boxes.

Also how to add the two arrows between the boxes?

Answer 1

You can use the label option for already existing nodes or you can use new \nodes; in the example below I used both this approaches:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes,positioning,arrows,calc}

\begin{document}

\begin{tikzpicture}[stack/.style={
  rectangle split, rectangle split parts=5, draw, anchor=center},
  myarrow/.style={single arrow, draw=none}]

\node [stack] (ini)  {$a=0$\nodepart{two}$b=10$%
   \nodepart{three}$c=100$\nodepart{four}$d=-10$\nodepart{five}$\cdots$};

\node [draw,rectangle,align=left,right=of ini,label=above:{Computer Program}] (mid)
  {instruction 0;\\ instruction 1;\\$\ldots$\\instruction $n$;};

\node [stack,right=of mid] (fin) {$a=10$\nodepart{two}$b=100$%
  \nodepart{three}$c=-10$\nodepart{four}$d=110$\nodepart{five}$\cdots$};

\node [above=of ini,anchor=north,align=left] {Initial values of\\variables};
\node [above=of fin,anchor=north,align=left] {Final values of\\variables};

\node [myarrow,draw,anchor=west] at ($(ini.east)+(2.5pt,0)$) {\phantom{te}} ;
\node [myarrow,draw,anchor=west] at ($(mid.east)+(2.5pt,0)$) {\phantom{te}} ;

\end{tikzpicture}

\end{document}

A little additional example just to illustrate the two mentioned methods to place labels next to nodes (the second example requires the positioning library):

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}

\begin{tikzpicture}[mynode/.style={draw, anchor=center}]

\node [mynode,label={label}] at (0,0)  {test node};
\node [mynode,label=below:{label}] at (0,-2)  {test node};
\node [mynode,label=west:{label}] at (0,-4)  {test node};
\node [mynode,label=east:{label}] at (0,-6)  {test node};
\node [mynode,label=east:{label1},label=west:{label2}] at (0,-8)  {test node};

\node [mynode] at (6,0) (a) {test node};
\node [above=2mm of a] {label1};
\node [below right=2mm of a] {label2};
\node [below left=4mm of a] {label3};
\end{tikzpicture}

\end{document}

Answer 2

I made some modification from Gonzalo's answer. I remove two libraries calc and positioning and I modified some styles. I changed the order of the creation of the nodes. (stack) -> (Arrow)-> (stack) -> (Arrow)-> (stack)

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}

\begin{document}


\begin{tikzpicture}[every text node part/.style={align=left},
                     stack/.style={rectangle split, 
                                   rectangle split parts = 5, 
                                   draw,text width=1.5cm},
                    myarrow/.style={single arrow,
                                    draw,
                                    right = 3pt,
                                    minimum size = 5ex}
                  ]
% we start
\node [stack] (ini)  {%
                      $a=0$     \nodepart{two}
                      $b=10$    \nodepart{three}
                      $c=100$   \nodepart{four}
                      $d=-10$   \nodepart{five}
                      $\cdots$};
% we add an arrow
\node [myarrow] (A) at (ini.east) {} ;  
% after the arrow, the main node at the end
\node [draw,rectangle,align=left,right=3pt] (mid) at (A.east)
            {instruction 0;\\ 
             instruction 1;\\
             $\ldots$\\
             instruction $n$;};
% we add another arrow
\node [myarrow] (B) at (mid.east) {} ;   
% after the arrow, the final node 
\node [stack,right=3pt] (fin) at (B.east)  {%
                                            $a=10$    \nodepart{two}
                                            $b=100$   \nodepart{three}
                                            $c=-10$   \nodepart{four}
                                            $d=110$   \nodepart{five}
                                            $\cdots$};
% labels : I don't like vey much `label= ` it's a shortcut but I think it's more powerful and flexible to use real nodes.
\node [above,align=left]  at (ini.north) {Initial values of\\
                                          variables};
\node [above,align=left]  at (fin.north) {Final values of\\
                                          variables};
\node [above]             at (mid.north) {Computer Program};   

\end{tikzpicture}
\end{document}