off-by-one error n. Exceedingly common error induced in
many ways, such as by starting at 0 when you should have started at
1 or vice-versa, or by writing `< N' instead of `<= N' or
vice-versa. Also applied to giving something to the person next to
the one who should have gotten it. Often confounded with
{fencepost error}, which is properly a particular subtype of it.