In engineering, abug is adesign defect in anengineeredsystem—such assoftware,computer hardware,electronics,circuitry ormachinery—that causes an undesired result. Defects outside the scope of design, such as a server crash due to anatural disaster, are not bugs, nor do bugs occur in natural systems such as theweather.
Bug is a non-technical term; more formal terms, besides defect, are error, flaw, andfault. Bugs may be persistent, sporadic, intermittent, or transient; in computing,crashes,freezes, andglitches are types of bug.
Since desirability is subjective, what is undesirable to one may be desirable to another, hence the often comical rejoinder occasionally offered to the report of a bug, "It's not a bug, it's afeature."
The Middle English wordbugge is the basis for the termsbugbear andbugaboo as terms used for a monster.[1]
The termbug to describe a defect has been engineering jargon since at least as far back as the 1870s, long before electronic computers and computer software. For instance,Thomas Edison wrote the following words in a letter to an associate in 1878:
It has been just so in all of my inventions. The first step is an intuition, and comes with a burst, then difficulties arise—this thing gives out and [it is] then that "Bugs"—as such little faults and difficulties are called—show themselves and months of intense watching, study and labor are requisite before commercial success or failure is certainly reached.[2]
In acomic strip printed in a 1924telephone industry journal, a naive character hears that a man has a job as a "bug hunter" and gives a gift of abackscratcher. The man replies "don't you know that a 'bug hunter' is just anickname for arepairman?"[3]
Baffle Ball, the first mechanicalpinball game, was advertised as being "free of bugs" in 1931.[4]
Problems with military gear duringWorld War II were referred to as bugs or glitches.[5]
In the 1940 filmFlight Command, a defect in a piece of direction-finding gear is called abug.
In a book published in 1942,Louise Dickinson Rich, speaking of a poweredice-cutting machine, said, "Ice sawing was suspended until the creator could be brought in to take the bugs out of his darling."[6]
Isaac Asimov used the termbug to relate to issues with a robot in his short story "Catch That Rabbit," published in 1944.
U.S. Navy Rear Adm.Grace Hopper, a computer pioneer, popularized a story about amoth that caused a problem in an earlyelectromechanical computer.[7] While Hopper was working on theMark II andMark III as Harvard faculty in about 1947, operators traced an error in the Mark II to a moth trapped in a relay. The moth was removed from the mechanism and taped in a log book with the note "First actual case of bug being found."[8]Reportedly, the operators, including William "Bill" Burke, later of theNaval Weapons Laboratory,Dahlgren, Virginia,[9] were familiar with the engineering term and probably making adouble entendrejoke by conflating the two meanings ofbug (biological and technical). Even if a joke, the story indicates that the term was commonly used in the computer field at that time.[10][11][12][13]The log book, complete with moth, is part of the collection of the SmithsonianNational Museum of American History.[12]
The related termdebug also appears to predate its usage in computing: theOxford English Dictionary's etymology of the word contains an attestation from 1945, in the context of aircraft engines.[14]
Sincebug implies undesirable behavior, calling out a bug is subjective. What some find a bug others may find a useful feature, hence the familiar phrase, "It's not a bug, it's a feature" (INABIAF).[15] This quip is recorded inThe Jargon File (1975) but dates at least to 1971, when thePDP-8 programmer Sandra Lee Harris ofDigital Equipment Corporation (DEC) made the distinction between issues to be fixed in the code for DEC'sFOCAL interpreter and those to be documented or clarified in the user manual.[16]
Such behavior may be explicitly communicated to users or remainundocumented.
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