I'm not sure what made me remember this - maybe reading the MSDN article 
on file name validity. But here's a story for you...

At the school I went to, the teachers didn't really "believe in" 
electricity. They saw it as the work of Satan. It was a necessary evil 
because it pervades the Real World [a place most of the teachers had 
only read about], but it's something that children should be protected 
from as much as possible.

As you can imagine, when the Government created the National Curriculum, 
which insists that children have to learn about computers, it caused a 
bit of a stir. Eventually one of the old unused rooms in the school was 
kitted out with 6 RM Nimbus 80186-SX machines and a couple of colour 
dot-matrix printers. It then fell to one of the Religious Education 
teachers to read the manuals and find out how computers actually work, 
and then teach it to us.

I presume it goes without saying that as an experienced programmer with 
5 years of BASIC and 3 years of Pascal behind me, being taught how to 
draw rectangles with LOGO was hardly challenging material. It /was/ nice 
to be able to /type/ my English essays in Word 2.0 rather than write 
them by hand, however.

This was also roughly around the time the shareware version of DOOM 
appeared. One of my classmates was a big DOOM enthusiast. He managed to 
smuggle the disks in to school, and while no-one was looking, he hid a 
copy of DOOM on the school computer, in a "hidden" folder.

Now, baring in mind this was a school for stupid people, and Adam had no 
particular computer training, what he did was, in retrospect, quite 
clever. He hid DOOM in a folder named "..".

The first thing to notice is that, under MS-DOS, every directory listing 
always begins with a dummy directory entry for ".", followed by another 
dummy entry for "..". So adding a /real/ folder actually named ".." just 
causes this line to be repeated. A typical user ignores all the headers 
and footers and just looks at the meat in the middle; thus, in all the 
years we were at the school, nobody ever found this hidden folder.

The second thing to notice is that ".." is a reserved name. Every time 
you utter it, the computer interprets it as an /instruction/ rather than 
a /name/. This makes it bafflingly difficult to /do/ anything to this 
folder. Even if you notice it exists, you can't access it. Every time 
you utter it's name, the computer assumes you mean the parent folder!

DIR ..      Just lists the parent folder.
CD ..       Takes you to the parent folder.
DEL ..      Tries to delete the parent folder. (And fails, because 
you're currently inside it.)
RENAME ..   Also fails.

In short, each time you try to interact with this folder, something 
baffling happens. Baffling, that is, if your knowledge of computing is 
so limited that you had to actually read the manual just to figure out 
which cable plugs into which socket. ;-) If, on the other hand, you 
happen to be quite skilful with computers, you can figure out the 
special incantation to make DOS interpret the name as a literal name, 
rather than a command. And /then/ you can play DOOM! :-D

In a way, I guess it's like shooting fish in a barrel. When they got the 
shiny new 80286-SX, that had Windows 2 on it, and it was "locked" so you 
need a username and password to get in, and us kids only had privileges 
to run a few Windows applications. In particular, you couldn't exit to 
DOS. Only the staff can do that.

We knew, of course, that the username was "manager". Once again, it was 
Adam who cracked the password. It was "teacher". :-D

With such a level of computer sophistication, it seems a little 
premature to claim a technological victory. Our adversary clearly had no 
clue what they were doing.

On the first hand again, most of the kids in my school probably couldn't 
*spell* teacher correctly. :-P

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