August 29 --- Class 1  --- Introduction

Handouts:
	Syllabus
	Student Survey
	AWK tutorial (students are to print this)

Activities:

	Student Survey

		The survey was handed out when students entered.  If you
		did not hand one in at the end of class, please hand one
		in as soon as possible.  It is important for me to have
		an idea of everyone's computing and physics background.

	Class web page and syllabus

		We went over the class web page and the syllabus.  There
		were no questions.

	Setup accounts on nations cluster
		Use web page on class syllabus.  Requires network ID, password

		Everyone was asked to set up a nations cluster account
		before class.  A few people had to do it in class.  To
		get a nations cluster account select "STC Unix
		Workstatios".

	Introduction to MacOS
		Many of you are not familiar with MacOS, but hopefully
		you will become accustomed to it soon.  At the bottom of
		the screen is an application launcher called the "Dock".
		It shows running applications and has several lists of
		applications.  In the "developer" list, denoted by an
		icon with three dots, you will find the terminal
		application.  We will probably use the "xterm"
		application more frequently.

		Outside of the ADS cluster, many things are customizable
		by the user in a way that can make ones life much
		easier.  When I agreed to use the Apple cluster for this
		class, I did not realize how UITS has limited the Apple
		environment.  I will be working with UITS to try to get
		around some of these limitations.  Some of you who
		stayed after class saw me in a sometime vigorous
		discussion with the system manager of the Apple cluster.

		Starting X11

		To start X11, you need to locate it in the Finder
		application and then double click on the X11 line in
		finder or single click on the X11 icon that appears in
		the rightmost pane of Finder.

		Finder is the friendly face icon at the left side of the
		dock.  You can also get a Finder window by dragging on
		the Apple icon at the upper left hand corner of the
		screen.

		In Finder you will see an "Applications" directory in
		the leftmost pane.  Click on that and you will see all
		the files in that directory.  Click on the "Utilities"
		directory and anothe pane will show the files in
		Utilities.  Both the "Terminal" and "X11" applications
		are found in the Utilties directory.  Launch X11 and an
		"xterm" window will appear.  You can create additional
		xterm windows by holding down the "apple command key"
		(either side of the space bar) and the letter "n".  In
		the future, I will call such combinations Apple-N.
		(You don't need to capitalize the n.)

	Logging out
		To log out of the Apple, click on the apple icon in the
		left corner of the menu bar at the top of the screen.
		Drag down to the last line, which should say "Log out"
		and your user name.   (Of course, you don't want to log
		out now, but if you tell anyone how to log into a
		computer, make sure you tell them how to logout before
		leaving them.)

	Logging into Nations

		Because of the limitations of the way UITS has set up
		the Apple cluster, we will also use the Nations cluster.
		In an xterm, type this command:

		ssh -X nations

		You should be prompted for your kerberos password.  Type
		in your network password and you should be logged in.
		Anyone who still can't do this, should let me know and
		should seek help at the support office.

		ssh stands for secure shell.  I use it to get into
		computers all over the country where I have accounts and
		do work.  The -X option should set up forwarding of you
		X11 session.  It is important to use a capital X.  A
		lower case x will have the opposite effect.

		Once on the nations cluster, we needed to set up the
		environment for future work.  It is very important to
		carry out these steps and most people did it in class.

	Modify path variable
		Executables for class exercises will appear beneath my home 
		directory in a subdirectory ~sg/bin
		To add this directory to your path, look for the first
		line in your ~/.cshrc file that starts with
		set path
		Add ~sg/bin just before the closing parenthesis

		You can use any editor that you like to change the file.
		Of course, that editor has to be on the Nations cluster.
		I am old and use the vi editor which predates the emacs
		editor.  emacs is very popular nowadays.  In the old
		days, I always knew that vi would be available, but many
		systems did not have emacs.  If you start emacs on the
		nations cluster, it should open a window on your apple
		screen.  You will probably be able to use the arrow keys
		and mouse to move the cursor around the screen.

	Setting DISPLAY and permissions

		One of the wonderful things about the X Windows system is
		that it lets you pop up a window on a machine different from
		the one on which the program creating the windoe is running.
		If you make a beautiful graph you can show it to a friend in
		Alaska by setting the DISPLAY to be the computer in Alaska
		your friend is sitting in front of.  However, before we try
		that, the first thing is to make sure that you can display a
		graph from nations on your apple computer.

		This command typed into the window you used to log into
		the nations cluster may display a blank graph on your screen:

		axis </dev/null |plot -T x

		If you get the complaint: axis: Command not found., then the
		directory that contains axis is not in your path.  On the 
		Nations cluster, 
		/usr/local/bin/axis </dev/null | /usr/local/bin/plot -T x
		will avoid the problem of not having axis or plot in your path.

		If you don't get a graph at this point, it is either because
		your DISPLAY environment variable is not correctly set, or you
		do not have permission to create a window on your screen.
		If you used the -X option when you ran ssh, this should
		not happen and you should be able to skip ahead.

		DISPLAY and xhost

		If the graph does not pop up, you need to worry about
		the details of making the connect between the computer
		that is going to create the window and the computer
		where you want that window displayed.

		If you edited your .cshrc file and you were able to
		display an empty graph from nations on your apple
		computer, you were finished for the day and could leave.
		In our next class, we will learn more about unix.
		Read on for details of what to do if the X11 forwarding
		is not working.

		The variable DISPLAY tells the application where to show the
		window.  That is, the DISPLAY can be set to your own computer,
		or to your friend's computer in Alaska.

		To find out the current value of the DISPLAY variable type:

		printenv DISPLAY

		To tell xplot on which machine to make the plot issue this
		command in the window where you will issue the axis command:
		  setenv DISPLAY workstation:0.0
		For example:
		  setenv DISPLAY sioux:0.0

		The next issue is whether the computer on which you wish to
		display the window has granted permission for you to display
		a window.

		The person (probably you) who is working at the console of 
		the workstation where you want the window displayed must
		issue the xhost command to allow xplot to open a window on
		its screen.  Here is an example:
		  xhost + sioux
		This allows X processes running on sioux to open windows at
		whichever machine has been issued the above command.

		If you want to display a window on your friend's computer in
		Alaska, yuor friend in Alaska must issue the xhost command on
		the computer he or she is using.  For example, the person in
		Alaska types:

		xhost + sioux.ucs.indiana.edu

		to allow sioux.ucs.indiana.edu to display a window on the
		computer in Alaska.

		If you find that you have to issue these commands every time
		you log on to display a graph, you might want to automate
		the process as described in the next paragraph.  On many
		systems, you might find that you do not need to do this.
		Also, if you use ssh to connect to a remote system, you might
		find that things are automatically set up so the DISPLAY and
		permissions are set up.  In fact, some oranizations now have
		"firewalls" to protect their networks what will stymie your
		efforts to set the DISPLAY.  So, when you start using a new
		machine, just try to display a graph or an xterm and see if
		you succeed before you start setting the DISPLAY or running
		xhost.

		You might want to do the above operations automatically every
		time you log in.  If so, to your .login file add:
		   setenv DISPLAY `hostname`:0.0
		   xhost + `hostname`
		
		If you plan to log in from elsewhere and display graphs
		remotely, you might want to add an alias like this to your 
		.cshrc file:
		   alias dcampy    'setenv DISPLAY campy:0'
		This would only work if campy's full name is 
		campy.ucs.indiana.edu, since the nations cluster is part of
		ucs.indiana.edu.  If you want to display on a physics 
		machine, give the full name of the machine.

		This is not the most enjoyable way to start a course in
		computational physics, but once you get things set up correctly
		you will reap the benefits for the rest of the semester and
		beyond.