How to print part of .tex code to pdf

My friends send me this .tex code, but it is only part of the code. I need your help to edit this code into a full document, because when I insert this code to TeXworks it does not compile into a pdf file.

This is the part of code which I need to be edited into a full document:

digraph {
A [peripheries = 2];
B [peripheries = 2];

A->B [label = "a"];
S->A [label = "a"];

A->A [label = "b"];
S->S [label = "b"];

A->S [label = "c"];
S->B [label = "c"];

}


Console output:

This is pdfTeX, Version 3.1415926-1.40.11 (Web2C 2010) restricted \write18 enabled. entering extended mode (./untitled-1.tex LaTeX2e <2009/09/24> Loading CZ hyphenation patterns: Pavel Sevecek, v3, 1995 Loading SK hyphenation patterns: Jana Chlebikova, 1992

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ...

                                               l.1 d
igraph { ?

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Welcome to TeX.SE. What is this code supposed to do? –  Peter Grill Nov 14 '12 at 2:04
its graph of automation –  user1779502 Nov 14 '12 at 2:09
Please, post your preamble. Are you trying to compile only this code? –  Sigur Nov 14 '12 at 2:14
Try dot2tex maybe: fauskes.net/code/dot2tex –  Scott H. Nov 14 '12 at 2:21

To compile that code you would need a dot language interpreter (i.e. graphviz or equivalent) which through a package (or otherwise) could spit out TiKz (or equivalent) code. I don't have graphviz installed, but I do have Gephi installed. I made a .dot file that contains your code and had Gephi do the layout and then exported to TiKz. The result could be improved (label adjustments etc.) if I knew any TiKz but I don't so unfortunately I can't help you there. Below is the output and generated .tex file.

\documentclass{minimal}
\usepackage{tikz, tkz-graph}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}
\begin{document}
\definecolor{COLOR0}{rgb}{0.6,0.6,0.6}
\definecolor{COLOR1}{rgb}{0.0,0.0,0.0}
\pgfdeclarelayer{background}
\pgfdeclarelayer{foreground}
\pgfsetlayers{background,main,foreground}
\begin{tikzpicture}
\node at (0.8159795,0) [circle, line width=1, fill=COLOR0,  inner sep=0pt, minimum size = 5pt, label={[label distance=0] 315:A}] (1) {};
\node at (-1.6908659,4.5319248) [circle, line width=1, fill=COLOR0,  inner sep=0pt, minimum size = 5pt, label={[label distance=0] 315:B}] (2) {};
\node at (0.8748864,5.7434276) [circle, line width=1, fill=COLOR0,  inner sep=0pt, minimum size = 5pt, label={[label distance=0] 315:S}] (3) {};
\begin{pgfonlayer}{background}
\tikzset{EdgeStyle/.style = {->,shorten >=1pt,>=stealth, bend right=10}}
\tikzset{EdgeStyle/.style = {->, shorten >=1pt, >=stealth, bend right=10, line width=0.5, color=COLOR0}}
\Loop[dist=1cm,dir=EA,style={->,shorten >=1pt,>=stealth,line width=0.5}, color=COLOR1, label=b](1)
\Edge [label=a](1)(2)
\Edge [label=c](1)(3)
\Edge [label=a](3)(1)
\Edge [label=c](3)(2)
\Loop[dist=1cm,dir=EA,style={->,shorten >=1pt,>=stealth,line width=0.5}, color=COLOR1, label=b](3)
\end{pgfonlayer}
\end{tikzpicture}
\end{document}

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Googling digraph latex produced this:

You need graphviz.sty (available here) and you need the following in your document preamble:

\usepackage[pdftex]{graphicx}
\usepackage{graphviz}

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Where would one find your graphviz.sty? This answer seems a little useless without it. –  naught101 Nov 14 '12 at 5:05
The information in the answer, including a description of graphviz.sty, is from here. –  Andrew Uzzell Nov 14 '12 at 10:20
The fact that the OP tried to latex the code snippet as is suggests s/he does not know what a full latex document is. (As the error shows, the first line of the supposed latex file was digraph). A real answer should probably provide a full and compilable latex file. –  jon Nov 14 '12 at 11:29