<?xml version="1.0" encoding="ISO-8859-1"?> <!-- $Id: basics.xml,v 0.998 Exp $ --> <Chapter> <Heading> Introduction </Heading> The aim of this package is to turn <Package> GAP </Package> more user-friendly, at least for semigroup theorists. It requires the usage of external programs as is the case of <C>graphviz</C> <Cite Key="KoutsofiosNorth:2002"/>, a software for drawing graphs developed at AT <Alt Only="LaTeX"> \& </Alt> <Alt Not="LaTeX"> <Alt Only="HTML"> &amp; </Alt> <Alt Not="HTML"> & </Alt> </Alt> T Labs, that can be obtained at <URL>http://www.graphviz.org/</URL>. It is used not only to draw right Cayley graphs of finite semigroups and Sch{\"u}zenberger graphs of finite inverse semigroups but also to visualize in the usual way the egg-box picture of a D-classe of a finite semigroup. <Alt Only="LaTeX"> \ \\ \ \\ </Alt> <Alt Only="HTML"> <br><br> </Alt> <B>Important note</B>: The version of <C>graphviz</C> to install should be greater or equal to 1.16. <Alt Only="LaTeX"> \ \\ \ \\ </Alt> <Alt Only="HTML"> <br><br> </Alt> Tcl/Tk should also be available in order to run the graphical interfaces (XAutomaton and XSemigroup) used to specify automata and semigroups. </Chapter>