\magnification=\magstephalf
\parskip=0.2cm
\parindent=1.0cm
\def\simlt{\lower.5ex\hbox{$\; \buildrel < \over \sim \;$}}
\def\simgt{\lower.5ex\hbox{$\; \buildrel > \over \sim \;$}}
\tolerance=10000

\centerline{\bf IDL INFO AND A QUICK TUTORIAL}

\noindent {\bf 1. BASIC INFO ABOUT IDL.}

	 IDL is extremely powerful and in wide use by scientists, and
especially astronomers.  Unfortunately, there are no good primers for
the beginner. The best way to learn its basics is with the enclosed
tutorial. 

	A student version of IDL is available by getting on the web and
going to http://www.rsinc.com/academic.html.  Cost is \$79.  This
student version is good for two reasons: it has a good, comprehensive
book entitled ``Learning IDL'' and having your own copy of IDL at home
will allow you to develop software and reduce data in peace and quiet,
and help you a lot in learning IDL and figuring out its idiosyncrasies. 
We {\it strongly suggest} that you order your own copy of IDL.  ({\it
Note:} the student version will run on either PC or Mac.  It requires at
least 16 Mbytes of internal memory, 25 Mbytes (PC) or 40 Mbytes (Mac)
disk space, and comes on a CD. 

\noindent {\bf 2. LEARNING IDL.}

	Learning a computer language is like learning Greek. You become
more proficient as you use it. However, it helps to have a tutorial. We
envision {\it three levels} of tutorial:

	{\bf (1): THE NOVICE LEVEL.} To learn IDL at the basic level, we
suggest that you

	$\bullet$ Sit down at a computer for a couple of hours using
the attached tutorial.

\noindent This will allow you to write the software you need for your
first two lab reports.  {\it We can't overemphasize the importance of
this step!}

	{\bf (2): THE INTERMEDIATE LEVEL.} To become {\it proficient} at
IDL, we suggest that when you have some more time---i.e.  after you've
finished your first lab report---you

	$\bullet$ Sit down at a computer for several sessions of an hour
or two each with the IDL books entitled {\it USING IDL} and {\it
BUILDING IDL APPLICATIONS}.  Read the following sections in the order
given and try out everything, either using the examples they give or
making up your own: \hfil\break
        {\it USING IDL: Chapter 1}, {\bf Typographical Conventions} (pp
4 to 5).  \hfil\break
	{\it USING IDL: Chapter 2}, {\bf Input to IDL} (pp 13 to 16). 
\hfil\break
	{\it BUILDING IDL: Chapter 2}, {\bf Constants and Variables}, pp
12 to 21. \hfil\break
	{\it BUILDING IDL: Chapter 3}, {\bf Expressions and Operators},
pp 24 to 37. \hfil\break
	{\it BUILDING IDL: Chapter 5}, {\bf Array Subscripts}, pp 56 to
65. \hfil\break
	{\it USING IDL: Chapter 10}, {\bf X Versus Y Plots---PLOT and
OPLOT, Annotation---the XYOUTS Procedure, Plotting Symbols, Polygon Filling}
(pp 157 to 171); {\bf Plotting Missing Data} (pp 179 to 180); {\bf Using
the CURSOR Procedure} (pp 182 to 184).  \hfil\break
	{\it BUILDING IDL: Chapter 7}, {\bf Statements}, pp 80 to 104.
\hfil\break
	{\it BUILDING IDL: Chapter 8}, {\bf Defining Procedures and
Functions}, pp 106 to 115. 

\noindent This gives you the background to become an IDL ``expert''.

	{\bf (3): THE EXPERT LEVEL.} To {\it actually} become an IDL {\it
expert}, we suggest that you 

	$\bullet$ Purchase the IDL student version, install it on your
own computer, and read through manual bit-by-bit in front of your
computer. 

\noindent {\bf 3. RUNNING IDL IN ROOM 705.}

	Our IDL software runs only on two of our 6 machines, ttauri and
rrlyrae.  However, you can run IDL on these machines from any other
workstation by using the following procedure. 

	{\it First:} Because all IDL users are using these two machines,
it is best to share the load between the two machines.  Therefore, if
there are many people using IDL, then you should first check to see
which machine has fewer users and log onto that one.  To do this, type
the UNIX command

	{\it idlusers}

	{\it Next:} In order to run IDL, you must be on either ttauri or
rrlyrae.  If you are not sitting at the system console for one of these
machines, then do the following in UNIX (supposing, for example, that you're
on seyfert.ugastro.berkeley.edu:1, aka ``seyfert:1'')
and you decide to run IDL on rrlyrae):

	{\it seyfert $>$ xhost + rrlyrae}

	{\it seyfert $>$ rlogin rrlyrae}

	{\it rrlyrae $>$ setenv DISPLAY seyfert:1}

\noindent At this point, you sitting in front of seyfert:1 but are 
running on rrlyrae. You are in your
home directory, just as you were when you first logged into seyfert. Usually
people switch to a different subdirectory before starting IDL---for example,
a subdirectory containing relevant IDL data and/or program files. Suppose
you wish to do this (you don't have to) and you wish to run from the
\~/idl/testout subdirectory. Then your next command would be

	{\it rrlyrae $>$ cd idl/testout}

\noindent Finally, you are ready to run IDL by typing

	{\it rrlyrae $>$ idl}

\noindent That's it!

	We maintain a website with Frequently Asked Questions (FAQ's)
about IDL.  It's location is
http://www.ugastro.berkeley.edu/radiolab/control/faq.html (It's
accessible through the Radiolab homepage under High-Level Control
Software)

\noindent {\bf 4. QUITTING IDL IN ROOM 705.}

	To quit IDL, type 

	{\bf exit}

\noindent when you are in IDL. Then, if you are not sitting at either ttauri
or rrlyrae, you need to get back to your machine (seyfert:1 in the above
example) by entering (in UNIX)

	{\it rrlyrae $>$ logout}

\noindent This gets you off of rrlyrae and back to seyfert, leaving you 
with the UNIX prompt

	{\it seyfert $>$ }

\noindent {\bf 5. OUR TUTORIAL.}

	Our tutorial is based an early IDL tutorial book entitled {\it
IDL BASICS}. We provide here only specific sections of this book, the
ones required to get started and do what's necessary for your first lab
report. We also provide some additional information that we feel is
necessary for your initial forays into IDL-land.

	This book is out of print. We provide its title page and
table of contents so that you can get a little appreciation for what IDL
can do when you unleash its full power. 

\end
