\documentclass{minimal}
\pagestyle{empty}

\usepackage{pstricks}
\usepackage{pst-node}

\begin{document}

\begin{psmatrix}[mnode=oval, colsep=1.91cm, rowsep=1cm]
[mnode=R,name=vars]{\shortstack[l]{int s, z, c,\\\, strich, punkt;\\opcode aktop,opp;}} &
[name=calc]{\shortstack{\textbf{calc}\\z:=z*10\\+(c-'0');}} &
[name=null]{\shortstack{\textbf{null}\\aktop:=DONE;}} \\
%%
[mnode=R,name=res]{sys\_res} &
[name=sign]{\shortstack{\textbf{sign}\\s:=-1;}} &
[name=alu]{
	\shortstack{
		\textbf{ALU}\\
		siehe Codeschnipsel
	}
} \\
%%
[name=idle]{\shortstack{\textbf{idle}\\strich:=0;\\punkt:=1;\\opp:=NOP;}} &
[name=read]{\shortstack{\textbf{read char}\\z:=0;\\s:=1;}} &
[name=done]{\shortstack{\textbf{done}}} \\
%%
[mnode=R,name=void]{} &
[name=err]{\shortstack{\textbf{error}}} \\
\end{psmatrix}

\psset{arrows=->, shortput=nab}

\ncline[linestyle=dotted]{res}{idle}
\ncline[linestyle=dotted]{void}{err}
\ncarc[arcangle=24]{done}{idle}
\ncarc[arcangle=0]{err}{idle}

\ncarc[arcangle=0]{idle}{read}\ncput*[npos=.50]{do\_it$\uparrow$}
\nccurve[angleA=45,angleB=75,ncurvA=2,ncurvB=2]{read}{read}\ncput*{' '}
\ncarc[arcangle=0]{read}{sign}\ncput*[npos=.50]{'-'}

\ncarc[arcangle=0]{sign}{calc}
\ncarc[arcangle=50]{read}{calc}\ncput*[npos=.35]{c = '0'\dots{}'9'}
\nccircle[angleA=-20]{calc}{.78cm}\ncput*[npos=0.39]{c = '0'\dots{}'9'}
\nccircle[angleA=80,angleB=0,loopsize=0]{calc}{.66cm}\ncput*{' '}

\ncarc[arcangle=0]{calc}{alu}\ncput*[npos=.50]{aktop = '+','-','*','/'}
\ncarc[arcangle=0]{calc}{null}\ncput*[npos=.50]{aktop = '\textbackslash 0'}
\ncarc[arcangle=0]{null}{alu}

\ncarc[arcangle=0]{alu}{read}\ncput*[npos=.50]{calc\_done$\uparrow$}
\ncarc[arcangle=0]{alu}{done}\ncput*[npos=.50]{aktop == DONE}
\end{document}