off by one 

Off by one or OBO is a common error in computer program whereby a loop executes one time too few or too many. It occurs most commonly with complex vector or matrix scans.

Programmer 1: This program doesn't work. Take a look and see if there's anything wrong.
Programmer 2: Oh, this for loop is OBO. You aren't scanning the whole array.

off by one by Lezard Valeth May 23, 2003

off by one 

An "Off-By-One" (OBO) in a non-programming context is the act of a touch-typist beginning to type with their hands one key offset from home position.

If the typist in question types fast enough, the resulting nonsense string of gibberish resembling a 14 year-old's SMS history or YouTube comment may actually be sent/submitted before they notice what they've done.

Ex 1:
Sm "Pgg-Nu-Pmr" )PNP_ om s mpm-ptphts,,omg vpmyrcy od yjr svy pg s ypivj-yupody nrhommomh yp yupr eoyj yjrot jsmfd pmr lru pggdry gtp, yjr jp,r ppdoyopm/ (*That was actually harder than I thought it'd be, though notice the prevalence of things like omg and gtp)

Ex. 2:
Carly1992: Wanna come over to my place?
TCAPreditorBate: rirakky!
TCAPreditorBate: totally* Sorry, off by one

off by one by ZenAtWork May 28, 2010

Off-by-one 

Cyber attack, usually originating in Russia.

Sweden was off-by-one'd last night.

Off-by-one by addelindh May 19, 2016