Edit Note: I am trying to research "switches" (like
\chapter), which led to this question. It might be helpful to tag this "switches".
I have seen a lot of documentation that appears to be using the
@ symbol in a way that appears to separate a control sequence from a variable:
\@ptsizeThis control sequence is used to store the second digit of the pointsize we are typesetting in. So, normally, it’s value is one of 0, 1 or 2.
From: CTAN documentation on the "Book" class., also in Memoir, etc.
However in other documentation sources, there doesn't seem to be a need for the
@ symbol at all: LaTeX \if condition.
What is this symbol for, and more importantly: how should it actually be used?