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+\documentclass{article}
+\usepackage{../style}
+\usepackage{../langs}
+\usetikzlibrary{patterns,decorations.pathreplacing}
+
+\begin{document}
+
+\section*{Handout 4 (Unix-Style Access Control)}
+
+Access control is essentially about deciding whether to grant
+access to a resource or deny it. This sounds easy. Right? Well
+it turns out that things are not as simple as seem at first.
+Let us study as a case how access is organised in Unix-like
+systems (Windows systems have generally similar access
+control, although the details might be quite different).
+ 
+Following the Unix-philosophy that everything is considered as
+a file, even memory or ports, access control is organised
+around 11 Bits that specify how a file can be accessed. There
+are three modes for access \textbf{r}ead, \textbf{w}rite and
+e\textbf{x}ecute. Moreover there are .... owner, group and
+everybody else.
+
+
+
+\end{document}
+
+%%% Local Variables: 
+%%% mode: latex
+%%% TeX-master: t
+%%% End: