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This commit implements the .tex-based online help system in LON-CAPA. It
may be necessary to manually run loncom/build/help_graphics_converter.pl
and doc/help/rebuildLabelHash.pl after a cvs update, and
loncapa_apache.conf may need to be manually copied to /etc. (The
loncapafiles.lpml has been updated.)

After merging this, the URL http://[loncapahost]/adm/help/Foils.hlp
should display a help file.

Also, some *very* out-of-date files have been removed from the /doc
directory.

A script consists of several \textbf{statements}, separated by \textbf{semi-colons}.
A \textbf{statement\index{statement}} is the smallest kind of instruction
to the computer. Most problems will be built from several statements. 

A script can contain \textbf{comments}, which are not interpreted as statements
by the computer. Comments start with \textbf{\#}, and go to the end of that
line. Thus, if a line starts with \#, the whole line is ignored. Comments
can also begin in the middle of a line. It is a good idea to comment more
complicated scripts, as it can be very difficult to read a large script and
figure out what it does. It is a \emph{very} good idea to adopt some sort
of commenting standard, especially if you are working in a group or you believe
other people may use your problems in the future.

\begin{itemize}
\item One of the simplest statements in LON-CAPA is a \textbf{variable assignment}.
A \textbf{variable} can hold any value in it. The variable name must start
with a \textbf{\$}. In the \textbf{Script}, you need to assign to variables
before you use them. Put this program into the \textbf{Script} field of the
Numerical Response:

\begin{lyxcode}
\$variable~=~3;
\end{lyxcode}
This creates a variable named \textbf{variable} and assigns it the value
of {}``3''. That's one statement.

\end{itemize}
Variable names are \emph{case sensitive}, must start with a letter, and can
only consist of letters, numbers, and underscores. Variable names can be
as long as you want.