Off-by-one error

An off-by-one error is an exceedingly common computer bug induced in many ways, such as by starting at zero when you should have started at one or vice-versa, or by writing "< N" instead of "<= N" or vice-versa. Often confounded with fencepost error, which is properly a particular subtype of it.

The term "Obi-Wan error" is a sometimes used as a humorous synonym. The name is derived from the similarity between the phrase "off by one" and the name of the Star Wars character Obi-Wan Kenobi.

See also zeroth.

---

Article based on off-by-one error (http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi?query=off-by-one+errors) and "Obi-Wan error" at FOLDOC (http://www.foldoc.org), used with permission.