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I am a new Latex user and I have this question: What are the classes and packages that must exist in a simple Latex file?

Books recommendation are so appreciated.

marked as duplicate by Chris H, CarLaTeX, TeXnician, Andrew Swann, Zarko Aug 3 '17 at 10:09

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    Welcome to TeX.SE. Please take a look at the postings What packages do people load by default in LaTeX? and What are good learning resources for a LaTeX beginner? – Mico Aug 3 '17 at 8:53
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    I'm not clear at all what you mean here: as @Mico says perhaps 'what do people commonly load' but that's only one possible interpretation! – Joseph Wright Aug 3 '17 at 8:54
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    Incidentally, there can only be one \documentclass instruction per LaTeX document. Which document class you should use greatly depends on your typesetting needs -- about which, alas, you haven't told us anything so far. – Mico Aug 3 '17 at 8:56
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    One definition of a "simple" LaTeX file could be a file that loads no packages at all. But in practice there are some packages that are needed for almost any real document. – Chris H Aug 3 '17 at 9:11
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    A simple file could even not load any document class: \def\normalsize{\normalfont} \begin{document} Hello, {\em baby} \end{document} From here it depends of what you need. – Fran Aug 3 '17 at 11:47