# How do I draw box-and-pointer diagrams?

How do I draw box-and-pointer diagrams? For example, I'd like to illustrate what happens when you manipulate nodes in a linked list. Can I use MathJax?

Here is an example:

\newcommand{ptr}[1]{\overset{\mathtt{#1}}{\longrightarrow}} \begin{align*} &\mathtt{newNode} \\ &\quad\downarrow \\ \mathtt{head} \ptr{} \fbox{first} \ptr{next} &\fbox{another} \ptr{next} \mathtt{null} \\ &\fbox{second} \ptr{next} \fbox{rest} \ptr{next} \fbox{of} \ptr{next} \fbox{list} \ptr{next} \mathtt{null} \end{align*}

\newcommand{ptr}[1]{\overset{\mathtt{#1}}{\longrightarrow}} \begin{align*} &\mathtt{newNode} \\ &\quad\downarrow \\ \mathtt{head} \ptr{} \fbox{first} \ptr{next} &\fbox{another} \ptr{next} \mathtt{null} \\ &\fbox{second} \ptr{next} \fbox{rest} \ptr{next} \fbox{of} \ptr{next} \fbox{list} \ptr{next} \mathtt{null} \end{align*}


The key elements are:

• To get the $\mathtt{typewriter}$ font: \mathtt{the text}
• To create a $\fbox{box}$: \fbox{box}
• To draw an arrow $\longrightarrow$: \longrightarrow
• To label the arrow $\overset{\mathtt{label}}{\longrightarrow}$: \overset{\mathtt{label}}{\longrightarrow}
• To reduce code repetition, define a \ptr{label} command:

\newcommand{ptr}[1]{\overset{\mathtt{#1}}{\longrightarrow}}

• To make it span multiple lines:

\begin{align*}
first line &alignmentpoint something something \\
next line &alignmentpoint stuff \\
third line &alignmentpoint stuff
\end{align*}

• See also: MathJax basic tutorial and quick reference on Meta.Math.SE. May 1, 2014 at 17:38
• gah, why is there MathJax but no syntax highlighting on Meta? If <!-- language: lang-tex --> worked here, this would be more readable :/
– amon
May 1, 2014 at 17:41

I think it could be worth mentioning that http://yuml.me/diagram/scruffy/class/draw can be a nice picture-based alternative to the almighty MathJax, for perhaps simpler diagrams:

[Customer]<>-orders*>[Order]
[Order]++-0..*>[LineItem]
[Order]-[note:Aggregate root.]


• I love yUML *-* May 1, 2014 at 20:20
• Don't forget about the good old mspaint.exe! (It comes with free-hand circles!) May 1, 2014 at 21:01
• Just a note: on my work computer I can't see any images linked in questions/answers on SE, but math jax works just fine. For people like me, it's always a pleasure to see math jax used on a programming SE instead of enter image description here - the alt-text of the image.
– Shaz
May 1, 2014 at 21:04

It's almost a duplicate of @Mat's Mug answer, but there is also Scruffy that is an open-source desktop application designed to create yUML-like diagrams with a yUML-like syntax.

Morevoer, it also introduces some extensions to the yUML syntax and provides some basic support for sequence diagrams:

We really need to embed such a tool on some StackExchange sites. It would be priceless :)

                    +-------------------+
|TimerQueue (static)|
+-------+-----------+
|
+-----------+        +------v-------+          +-------------+
|TimerHolder+-------->TimerQueueTime+---------->TimerCallback|
+-----^-----+        +--------------+          +-----+-------+
|                                              |
|                                              |
+---+-+                                        +---v----+
|Timer<----------------------------------------+Cyclical|
+-----+                                        +--------+


It is too bad that since a few weeks they nag you for 3 dollars ;\

You can use Graphviz, possibly through its online version, GraphViz Workspace.

For example:

digraph {
node [ shape = box ];

a -> b;
b -> c;
c -> d1;
c -> d2;
}


You can use yEd (a desktop application). I especially like its grid mode, which allows you to position the boxes exactly the way you want, while keeping them evenly spaced.

Example:

I'm doing this with tikz; see for example the question I just posted on tex.stackexchange: