Source : Free On-Line Dictionary of Computing

TECO
     
         /tee'koh/ (Originally an acronym for "[paper]
        Tape Editor and COrrector"; later, "Text Editor and
        COrrector"]) A {text editor} developed at {MIT} and modified
        by just about everybody.  With all the dialects included, TECO
        may have been the most prolific editor in use before {Emacs},
        to which it was directly ancestral.  The first {Emacs} editor
        was written in TECO.
     
        It was noted for its powerful programming-language-like
        features and its unspeakably {hairy} {syntax} (see {write-only
        language}).  TECO programs are said to resemble {line noise}.
        Every string of characters is a valid TECO program (though
        probably not a useful one); one common game used to be predict
        what the TECO commands corresponding to human names did.
     
        As an example of TECO's obscurity, here is a TECO program that
        takes a list of names such as:
     
        	Loser, J. Random
        	Quux, The Great
        	Dick, Moby
     
        sorts them alphabetically according to surname, and then puts
        the surname last, removing the comma, to produce the
        following:
     
        	Moby Dick
        	J. Random Loser
        	The Great Quux
     
        The program is
     
        	[1 J^P$L$$
        	J <.-Z; .,(S,$ -D .)FX1 @F^B $K :L I $ G1 L>$$
     
        (where ^B means "Control-B" (ASCII 0000010) and $ is actually
        an {alt} or escape (ASCII 0011011) character).
     
        In fact, this very program was used to produce the second,
        sorted list from the first list.  The first hack at it had a
        {bug}: GLS (the author) had accidentally omitted the "@" in
        front of "F^B", which as anyone can see is clearly the {Wrong
        Thing}.  It worked fine the second time.  There is no space to
        describe all the features of TECO, but "^P" means "sort" and
        "J<.-Z; ... L>" is an idiomatic series of commands for "do
        once for every line".
     
        By 1991, {Emacs} had replaced TECO in hacker's affections but
        descendants of an early (and somewhat lobotomised) version
        adopted by {DEC} can still be found lurking on {VMS} and a
        couple of crufty {PDP-11} {operating systems}, and ports of
        the more advanced MIT versions remain the focus of some
        antiquarian interest.
     
        See also {retrocomputing}.
     
        {(ftp://usc.edu/)} for {VAX}/{VMS}, {Unix}, {MS-DOS},
        {Macintosh}, {Amiga}.
     
        [Authro?  Home page?]
     
        (2001-03-26)