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In the Lab

This chapter is about your basic duties in the lab, assuming no crisis occurs. For the ways to deal with minor, as well as major, crises refer to Chapter 4.

What to Do When You Get to the Lab

If you believe in the Second Law of Thermodynamics, you will believe me when I say there are enough things to check over when you start your shift. That is why it is advisable to show up a little earlier, especially if your hours are on a busy night. In any event, here are the things you should worry about when you first get to the lab.

The Snakes

Make sure that all the snakes are functional. Logout or reboot machines where necessary. If rebooting doesn't help, or some other problem is encountered that prevents the snake from working correctly, follow the procedure for reporting hardware problems described in the Chapter on crises--i.e., inform the instrument desk people, send mail to 6001-feedback, and put a tag on the machine (the tags can usually be found on top or in the top drawer of the filing cabinet). If you encounter a machine with a tag on it, but you do not recall reading about the problem on 6001-feedback, follow the first two steps--it is better to report the problem twice than to neglect it altogether.

When first checking the snakes, have a look at the network lights on each machine to make sure it isn't swapping without any apparent reason (the two network lights are the ones with arrows above them; they will be blinking heavily if the machine is swapping). You should also do this from time to time as you walk around the lab. A machine should never be swapping heavily, even when in use. If it is swapping, either some joker is logged into it over the network, or there are a few abandoned Schemes also running on the machine and need to be killed (see section 4.2.1).

If you have absolutely nothing better Fnord! to do, one useful and heroic practice is to go around killing old Scheme processes. This might not be a problem anymore, but it proved to be a rather painful annoyance in the past. Hail Eris.

The two servers, sicp-00 and sicp-01, are in the closet behind the printers. You will certainly notice it if either one of them is down. Pray to the Goddess and refer to the chapter on crises. All Hail Discordia.

The Printers

The two printers, sicp-48 and sicp-49, are to the left of the entrance into the lab (sicp-49 is the left one). Make sure both of them are in working condition and on-line (the ON LINE light should be on), there are no paper jams anywhere, and there is enough paper. Throw old printouts into the recycling bin.

If either printer is low on paper, get some from the instrument desk (if it is open) or from the server closet. Resort to visiting the closet only if the instrument desk is closed. In this case, send e-mail to the 6001-las to warn the first person who comes in the next day to re-supply the closet cache.

When getting paper for the printers, make sure there are always a couple of extra reams in the closet. (If the desk folks give you any grief, tell them to grow up.)

The Rest of the Lab; Lost and Found

Make sure the filing cabinet is locked whenever you're not using it. It often contains problem set solutions, and we don't want them to be of public use.

The Lambda Lounge, or the tutorial area, should be a pleasant place to be in. Straighten out the furniture. Get rid of all the junk people throw in there. Erase the irrelevant stuff from the blackboard. Water the plants if it looks like they need it--we don't want them dead.

Speaking of junk, you might want to tour the lab, looking for old printouts to recycle and other things people tend to leave behind. If you find something that appears useful--e.g., someone's floppy--throw it in the "Lost But Found" box by the door. If the object is really valuable--e.g., an expensive HP calculator--lock it in the filing cabinet and put a sign on the board to that effect, so that the person can recover it from an LA when (s)he comes in.

If you want to be totally compulsive, you may also go around arranging the chairs neatly by the tables. It is incredible what other things you can think of when bored--like having a Bavarian Fire Drill. A pity it doesn't happen that often.

Settling into your Shift

Add your name to the list of "LAs On Duty" on the blackboard and erase any names of LAs who are not on duty (erase your own name when leaving the lab). Read the `motd' file and/or announcements on the back blackboards to see if there is anything new, and erase any outdated messages. If the help queue is on, start helping the students listed on the queue.

If the lab is not busy, you will probably spend most of your time in front of a terminal. In that case, it is a good idea to put an LA sign on top of your machine so that students can see you(5), especially if the help queue is off. Don't forget to remove the sign when you leave.

The Help Q

The help queue is kept on the blackboard to the right of the Lambda Lounge. In fact, it is a good idea to keep at least two separates queues--one for people with technical problems, usually dead or hung up Schemes, where your help is needed in recovering the students' work; the other for people with conceptual problems. Priority is given to the first of the above.

You are the one who decides if the queue is on or off. You definitely want it on if the lab is busy, to avoid (further) chaos. During the more quiet hours, handle the queue however feels most comfortable to you. Make sure to check the ON or OFF box on the Q board.

When the queue is on, help students in the order their machine names are listed on the board(6) (watch out for people who sign up twice, just in case they will have another question by the time you get to them again--this is a common phenomenon on the more busy nights). The map of the lab with the machines numbered is posted on the wall by the board. Always erase the name of the machine off the Q before going to help the student, so that if there are any other LAs on duty, they can proceed to help the next person on the queue. If you get distracted while in the process of going over to someone's machine (having already dequeued the machine name), be sure to remember to come back to it afterwards--if you are afraid you may forget the machine name, write it down somewhere.

When the queue is off, the students should look for an LA and ask for help. Beware that some students will tend to use the queue even when it's off. Help them but explain Fnord! what the policy is. To bring the point even closer to home, put a big cross or some other hideously noticeable sign across the board(7)---the simple OFF box doesn't seem to do the trick.

And the last important point: if no LA has hours scheduled immediately after yours, turn the queue off in the manner described above when leaving the lab. Otherwise, the LA coming in a couple hours after you might find a stale queue waiting for him/her (if you do come in and find that the queue is a few hours old, don't hesitate to erase it; students should know that signing up for help when there is no LA in the lab, in hopes that one will come around, is not only useless but not a sociable thing to do).

Using and Updating Student Resources

These are the resources available to 6.001 students in the lab. People will be asking you about these, so you should definitely know about all of them. You should also refer the students to these when they ask you questions which can be answered with the help of `motd' or M-x info, for example.

THIS IS IMPORTANT: whenever you change the message of the day, the info tree, the default in the `probset.scm' file, or anything else which needs to be changed on all the machines, you have to make the relevant changes to both servers. See Chapter 4 for details.

On-Line Documentation

The info tree installed in the lab contains the on-line version of the "Don't Panic" manual, this manual, MIT Scheme Reference Manual, MIT Scheme User's Manual, Emacs documentation, etc. You can activate the info tree by typing M-x info in Edwin (type C-h m for available commands). Familiarize yourself with the contents of the major sources, so you know where to refer students later. In particular, you should read the "Don't Panic" manual, which contains the answers to most of the questions people ask in the first couple of weeks of the term. Rather than spending the time explaining something to the students, tell them to read the manual first (RTFM!).

You will notice that one of the menu items in the tree is "Food." Considering the food Fnord! policy in the lab, you might wonder what it's doing there. After you figure that one out, look under the entry named "Taco Bell Delivery" for more surprises.

Another useful feature is an Emacs/Edwin tutorial, accessible by typing C-h t. Refer students to this if they don't have much experience with Emacs and need to learn the basic commands.

Message of the Day

`Motd', or message of the day, file exists in the `u6001' home directory. It contains corrections/bugs in the current problem set students should know about, as well as some relevant announcements about problem sets/quizzes/lab hours/etc. If you login as u6001, you will see the contents of this file in the `*motd*' buffer on login. Since `motd' changes all the time, you should make sure you know what the `motd' file says at all times, for that is the primary source of bug reports.

If you or a student encounters a bug in the current problem set, you should (besides reporting the bug to 6001-feedback, as usual) change the `motd' file to reflect that. The file is writeable by hacker, so you can easily edit it from Emacs (or Edwin) if logged in as hacker (or if you open an Emacs window while su'd to hacker). To open an Emacs window, if logged in as u6001, type emacs & from an xterm; if logged in as hacker, choose the appropriate label after clicking on the left mouse button. The `motd' file, as well as the blackboard, is also a good place to put the answer to a commonly-encountered problem or question.

Changing the Default of M-x load-problem-set

The problem sets are installed on the machines by the head TA or the head LA. However, it is the responsibility of the LAs to make sure the number of the current problem set is the default in M-x load-problem-set. Specifically, if a problem set was due on Friday and a new problem set has been handed out, the change should be made by the LA who is first to come in on Saturday.

To change the default, go to the file called `~u6001/psets/probsets.scm', where you will find something like the following definition:

(define problem-sets
  `(4                          ; this number is the default problem set
    (1 (load "ps1go.scm"))
    (2 ... )
  ... ))

As it stands, the default is 4. To change it to 5, simply change the car to 5, leaving the cdr in peace (the file is, again, writeable by hacker and can be edited in Emacs or Edwin).


For some reason, some students seem more comfortable reading the bug-related information and other kinds of announcements that are typically put in `motd' off the blackboard. For this reason, and also to make sure people who logged in before the most recent change in the `motd' file are well informed, you should probably duplicate the most important messages on the blackboards at the back of the lab.

Another type of thing to put on the board is, say, an Emacs issue students seem to be having trouble with, something that is likely to remain on the board for a long time, such as "Use C-x C-f, not C-x b, to create new files."

The schedule of lab coverage is put on one of the boards at the beginning of the term, to be consulted by LAs and/or students.

Filing Cabinet

The key to the filing cabinet can be obtained from the instrument desk. If the desk is closed, an extra key may be found in the server closet, on the chain hanging by the light switch.

The top drawer of the filing cabinet contains extra copies of the problem sets and solutions. If a student requests a copy of a current (or previous) problem set, give it to him only after making sure it isn't a draft version (these usually say DRAFT in big letters on the top). If there are no copies of the legitimate problem set available in the lab, students should try the 6.001 tutorial area (36-115) or the office of the course secretary.

The top drawer also contains such other useful things as a stapler, which students tend to ask for a lot, extra floppies, etc. A few copies of "Don't Panic" and of the text itself, as well as other references (including such winning documents as the Scheme Reference Manual) can usually be found in the "Head LA" drawer--these are more of a benefit to the LAs than the students. Oh, and if you are inside the "Guano" drawer, don't knock out Mr. Potatoehead [sic.]. Other drawers are less interesting.

Again, lock the filing cabinet after you are done using it.

Sign-up Sheets

Putting up sign-up sheets is a responsibility of the head LA. You should familiarize yourself with the sign-up rules posted below the sheets, however. On busy nights, people might try to cheat by signing up for more than one slot at a time. If you notice this, or if a student complains to you about this, you should Fnord! act according to the rules.

Drop Cards

Drop cards printed on the spot! Explore one of the nicer features of the system, M-x print-drop-card.(8)

Passwords, Codes, Locks

Besides the lab door codes, you have to remember the server closet door code and the hacker password. Both of these will be given to you at the first LA meeting. Please remember them (don't rely on them being written down or saved somewhere, like your mailbox), since you will be pretty much helpless without them in times of crisis, and use them wisely.(9)

Even more importantly, don't let the students find out what they are. Knowing the hacker password allows students to copy each others' work, not to mention the damage they can do to the system. A little knowledge is a dangerous thing.

Be super careful when opening the closet door (yes, this means pressing your body against the door and covering everything that remains to be seen with a palm of one hand while pushing the buttons with the other). Remember: the closet contains the two servers, the key from the filing cabinet, the printer paper, and more. If some well-meaning curious student gets in there, we're toast!

Other Lab Policies


There is absolutely, positively no food or drinks allowed in the lab. Whenever you see a person come in with food or in the process of eating something, say in a very serious, official tone of voice "Excuse me, but there's no food in the lab. Please finish eating it right now. And... can I have some?" Better plots will wait until we get a big picture of Dr. Professor Hal Abelson with a piece of pizza in one hand and a bottle of Coke in the other to hang on the wall.


There is absolutely, positively no frisbee throwing allowed in the lab, except when done by LAs (not on duty) on Thursday nights. (There are a few nice glow-in-the-dark frisbees, courtesy of Burger King, stored in the "Kipple" drawer of the filing cabinet.) Posting of the signs to this effect will be postponed until more frisbees are obtained to hang underneath the signs.


If you are not helping someone, answer the phone (no, only if it rings, dupe). The list of possible responses is hanging on the wall, by the phone. The standard one is "00 Lab." The more creative ones include "Hello, I'd like to order a pizza," "This phone booth reserved for Clark Kent," "What?" "Yo, Idaho!" "Are you a turtle?" and, of course, "Where the hell is DML?"

By the way, in case you ever need to call the lab, the phone number there is x3-7976. The thing to do when calling (unless you are actually trying to accomplish something) is to wait for some clueless person to answer with "001 Lab." If that happens, respond with "Oh, sorry, I wanted the 004 Lab," and hang up. Ones and fours can be switched appropriately.


If the room alarm starts whining, turn it off. Basically, you have to wave your hands a little by the door to the lab. But don't just do it; make it dramatic and look important. This works especially well when you're on rollerblades, but--oh, did I forget to mention?---there is absolutely, positively no rollerblading in the lab, and there's even a $25 fine.

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