Input to LaTeX is plain text (ascii) which includes both the text of the
document and also formatting commands. It is possible to
split the input into several files using:
Space characters separate words. Two space characters in a row are
equivalent to a single space character. The end of line is also
equivalent to a space character. (However, a percent sign,
%, can end a line without
generating a space character.) Generally, space characters at the beginning
of a line are ignored.
An empty or blank line between two lines of text defines
a new paragraph.
Two blank lines are equivalent to one.
If entered directly in the input they cause LaTeX to do something special.
You can get the following seven of them into your document by simply
preceding them with a backslash (\):
$ & % # _ { }
To get the other three ( ~ ^ \ ) in
your output requires more work.
LaTex Commands
Commands take one of two forms
a backslash (\) followed by a single special character
a bacslash (\) followed by a string of letters
The second case is case-sensitive;
\Gamma is different from
\gamma.
These commands are terminated by a nonletter, i.e., a blank, a number,
a punctuation mark or special character.
Commands may have mandatory arguments, which are input in braces
({}).
They may also have optional arguments, which are input in square brackets
([]).
For commands which produce text a trailing blank may be interpreted as the
end of the command, which does not automatically create a space, so
you may have to do something to create an
interword space after this text.
LaTeX input normally begins with a
\documentstyle command. (In LaTeX2e
this is replaced with a \documentclass
command.)
The beginning of the document text follows a \begin{document}
command.
Input between the \documentstyle and \begin{document}
is called the preamble and typically contains new
command definitions, information for the
title, declarations
which affect things like Typefaces, etc.
The document text (and generally also the LaTeX input) is terminated by a
\end{document} command.
It is possible to obtain some of the input from external
files, i.e., those which are not the main file input to the LaTeX program.