Dot language

Command to generate image with dot

dot -Tpng -o Output.png Input.dot

Frequently used attributes

digraph G {
  graph [
    label="Show general attributes\n that can be used",
    labelloc=t,    //t=top, b=bottom
    labeljust=r,   //r=right justified, l=left justified
    overlap=false, 
    center=true, 
    bgcolor=green, 
    fontcolor=red, 
    fontsize=24, 
    rankdir=TB,   // Orientation: TB=Top to Bottom, LR=Left to right
    URL="G.html",  // Need to generate as ismap to be clickable
    nodesep=3.0  // increases the separation between nodes
        ];
  node    [shape=circle, style=filled, fontname="Courier"];
  edge    [color=blue]; // dir="none"
 
  a [label="Node A", width=1.25, fillcolor=white, color=black, URL="A.html"];
 
  {rank=same; "b"; "c";}
 
  a -> b [ taillabel="Tail Label", labelangle=45, labeldistance=5, color=red, fontcolor=blue];
 
  b -> c [ headlabel="Head Label", 
    labeldistance=2, 
    color=transparent, 
    dir=back     // back=Revert arrow direction, both=arrow on both ends
    URL="b.html"       // Need to generate as ismap to be clickable
     ];
 
  external_image [label="", shape=box, style=invis, shapefile="image.png"];
}

References

Node, Edge and Graph Attributes http://www.graphviz.org/doc/info/attrs.html#k:arrowType http://www.graphviz.org/doc/info/arrows.html