quine

quine: /kwin/ n.  [from the name of the logician Willard
   van Orman Quine, via Douglas Hofstadter] A program that generates a
   copy of its own source text as its complete output.  Devising the
   shortest possible quine in some given programming language is a
   common hackish amusement.  Here is one classic quine:

     ((lambda (x)
       (list x (list (quote quote) x)))
      (quote
         (lambda (x)
           (list x (list (quote quote) x)))))

   This one works in LISP or Scheme.  It's relatively easy to write
   quines in other languages such as Postscript which readily handle
   programs as data; much harder (and thus more challenging!) in
   languages like C which do not.  Here is a classic C quine for ASCII
   machines:

     char*f="char*f=%c%s%c;main()
     {printf(f,34,f,34,10);}%c";
     main(){printf(f,34,f,34,10);}

   For excruciatingly exact quinishness, remove the interior line
   breaks.  Some infamous {Obfuscated C Contest} entries have been
   quines that reproduced in exotic ways.