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Why do LaTeX internal commands have an @ in them?
What do \makeatletter and \makeatother do?
What is the difference between \myname and \my@name while writing a .cls file?

I have tried a few times to write/understand other peoples packages. Though I'm no good yet, I keep running into a definition using @ or @@ in the name. Why is this done ? Is there any special meaning ? Is this in any way related to the use of _ and __ in python, where a variable starting with @ shouldn't really be messed with while one with __ definitely should not be messed with ?

As an example :

\@author is used in the class files article.cls but is not defined anywhere. So I assumed the @ to mean it was some kind of command internal to LaTeX/TeX. While in a custom class file (res.cls by Michael DeCorte to be exact) I've seen \@name is specifically defined as both

\def\name#1{\def\@name{#1}}

and

\def\@name{}

To my knowledge the latter ensures a default value is set up in case the \name command is not used by the document writer. But this still doesn't indicate why the @ is used.

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marked as duplicate by egreg, Caramdir, Werner, Martin Scharrer May 14 '12 at 22:05

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
Welcome to TeX.sx! A tip: If you indent lines by 4 spaces or enclose words in backticks `, they'll be marked as code, as can be seen in my edit. You can also highlight the code and click the "code" button (with "{}" on it). –  Martin Scharrer May 14 '12 at 21:58
    
We had this question before. I'm currently looking for it. –  Martin Scharrer May 14 '12 at 22:01
1  
Maybe this answer helps? –  cgnieder May 14 '12 at 22:02
    
Oh dear, I did search for @ in the search bar and didn't get a response, that's why I posted I didn't realise it was a duplicate, sorry. –  Carel May 14 '12 at 22:54
    
@Carel: No worries. It is pretty much impossible to search for this. –  Caramdir May 15 '12 at 0:25

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