Dot http://www.graphviz.org/allows you to draw unidirectional graphic charts. Doxygen makes use of dot to get the graphics. To get dot emerge graphviz create a file as

digraph G { 
 main -> parse -> execute;
 main -> init [label="Reset"]; 
 main -> cleanup;
 execute -> make_string; 
 execute -> printf; 
 init -> make_string;
 main -> printf; 
 execute -> compare;  
}

Then create a gif: dot -Tgif ex1.dot -o ex1.gif

After that you get

Figure 10.1. DOT

lines starting with

# are comments

States need names that have to follow restrictions as not having spaces and being on a single line. If this is not what is desired, then they can be formatted:

name [shape=box, label=<This will <BR/>be put on<BR/>different lines<BR/> in a shaped box>, style="rounded,filled",fillcolor="grey"];

The same way also transactions can be formatted

State1 -> State2 [style=dotted, color=red, label="this is a transaction"];

It is also possible to modify the default settings

node [shape=box,style="rounded,filled",fillcolor="grey"];
edge [fontsize=10, color=darkgreen];
rankdir=LR;