A virtual turing machine (vtm)

 See http://cs.marlboro.edu/courses/spring2011/formal_languages/code/vtm/
 for these files. This command line app is installed on cs, 
 at /usr/local/bin/vtm .

Install notes :

 The way that this thing runs is a bit awkward,
 mostly because the way shebang scripts and arguments interact,
 but also because its had several authors.

 VTM.pm is a perl module, which has the guts of the "Virtual Turing Machine".
 vtm.pl is a command line script which process arguments and then runs VTM.pm.
 vtm.c is a wrapper around vtm.pl, to create a vtm* executable

 Two of these (vtm.pl and vtm.c) need hard-coded full directory paths
 to do their business.

 So after downloading and unpacking the archive :
  (0) You'll need perl installed; type "which perl" at the command line
      to see if you have it.
  (1) Decide where you want these files - anywhere - and move them there.
      (The executable vtm* can be copied to e.g. /usr/local/bin/ later.)
  (2) Edit VTM.pl and vtm.c to reflect the locations of the files.
      (Search for "where VTM.pm lives" in vtm.pl; vtm.c is pretty clear.)
  (3) Compile the .c program  with e.g. "gcc vtm.c -o vtm"
  (4) Copy the executable vtm to somewhere in your search PATH, 
      e.g. /usr/local/bin/vtm

 Then once you've created a *.vtm text file, such as machine/even.vtm, 
 with a first line that looks something like this :

   #!/usr/bin/env vtm -b_ -sEven -t10110010100 

 which means that 
   _               is the blank character, 
   Even            is the start state, and 
   10110010100     is the starting tape (with the head at the left)

 make it executable with 

   $ chmod +x even.vtm

 and run it with things like

   $ ./even.vtm          # built-in arguments
   $ ./even.vtm -0       # don't show progress; just show last state
   $ ./even.vtm -t       # ask user for starting tape
   $ ./even.vtm -t1011   # run with starting tape 1011

Shebang gotcha:

 One more problem: the /usr/bin/env first line seems
 to behave differently on different systems. In particular,
 some (like cs) don't seem to treat command line args 
 on the shebang line nicely after /usr/bin/env .

 So here on cs, I've epxlicitly put /usr/local/bin/vtm 
 as the shebang line. 

 That means that these *.vtm files will work as is
 only if you put vtm in that same place. Otherwise,
 you'll need to adjust the first line of the .vtm's.