0

0  Numeric zero, as opposed to the letter `O' (the 15th
   letter of the English alphabet).  In their unmodified forms they
   look a lot alike, and various kluges invented to make them visually
   distinct have compounded the confusion.  If your zero is
   center-dotted and letter-O is not, or if letter-O looks almost
   rectangular but zero looks more like an American football stood on
   end (or the reverse), you're probably looking at a modern character
   display (though the dotted zero seems to have originated as an
   option on IBM 3270 controllers).  If your zero is slashed but
   letter-O is not, you're probably looking at an old-style ASCII
   graphic set descended from the default typewheel on the venerable
   ASR-33 Teletype (Scandinavians, for whom Slashed-O is a letter,
   curse this arrangement).  If letter-O has a slash across it and the
   zero does not, your display is tuned for a very old convention used
   at IBM and a few other early mainframe makers (Scandinavians curse
   *this* arrangement even more, because it means two of their
   letters collide).  Some Burroughs/Unisys equipment displays a zero
   with a *reversed* slash.  And yet another convention common on
   early line printers left zero unornamented but added a tail or hook
   to the letter-O so that it resembled an inverted Q or cursive
   capital letter-O (this was endorsed by a draft ANSI standard for
   how to draw ASCII characters, but the final standard changed the
   distinguisher to a tick-mark in the upper-left corner).  Are we
   sufficiently confused yet?