In engineering, a bug is a

design A design is the concept or proposal for an object, process, or system. The word ''design'' refers to something that is or has been intentionally created by a thinking agent, and is sometimes used to refer to the inherent nature of something ...

defect in an engineered

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

that causes an undesired result. Although used exclusively to describe a technical issue, ''bug'' is a non-technical term; applicable without technical understanding of the system. The term ''bug'' applies exclusively to a system that is (human) designed; not to a natural system; and that the issue is within the influence of human control. For example, humans have faults but not bugs, and a server crash due to natural disaster is not a bug. In addition to or instead of ''defect'', some use: error, flaw or fault. Engineered systems is a broad classification encompassing but not limited to:

software Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital comput ...

computer hardware Computer hardware includes the physical parts of a computer, such as the central processing unit (CPU), random-access memory (RAM), motherboard, computer data storage, graphics card, sound card, and computer case. It includes external devices ...

electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

, circuitry and

machinery A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolec ...

. The undesirable result can be classified and described ''many'' ways including: intermittent, transient,

glitch A glitch is a short-lived technical fault, such as a transient one that corrects itself, making it difficult to troubleshoot. The term is particularly common in the computing and electronics industries, in circuit bending, as well as among pl ...

, crash or hang. Since desirability is subjective, what is considered undesirable to one may be considered desirable to another; even a useful feature.

History

The Middle English word '' bugge'' is the basis for the terms '' bugbear'' and '' bugaboo'' as terms used for a monster. The term ''bug'' 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 Thomas Alva Edison (February11, 1847October18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventions, ...

wrote the following words in a letter to an associate in 1878: In a

comic strip A comic strip is a Comics, sequence of cartoons, arranged in interrelated panels to display brief humor or form a narrative, often Serial (literature), serialized, with text in Speech balloon, balloons and Glossary of comics terminology#Captio ...

printed in a 1924

telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...

industry journal, a naive character hears that a man has a job as a "bug hunter" and gives a gift of a

backscratcher A backscratcher, sometimes known as a scratch-back, is a tool used for relieving an itch in an area that cannot easily be reached just by one's own hands, typically the human back, back. Although the backscratcher was an early human invention, Pr ...

. The man replies "don't you know that a 'bug hunter' is just a

nickname A nickname, in some circumstances also known as a sobriquet, or informally a "moniker", is an informal substitute for the proper name of a person, place, or thing, used to express affection, playfulness, contempt, or a particular character trait ...

for a repairman?" Baffle Ball, the first mechanical

pinball Pinball games are a family of games in which a ball is propelled into a specially designed table where it bounces off various obstacles, scoring points either en route or when it comes to rest. Historically the board was studded with nails call ...

game, was advertised as being "free of bugs" in 1931. Problems with military gear during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

were referred to as bugs (or

es). In the 1940 film, '' Flight Command'', a defect in a piece of direction-finding gear is called a ''bug''. In a book published in 1942, Louise Dickinson Rich, speaking of a powered ice cutting machine, said, "Ice sawing was suspended until the creator could be brought in to take the bugs out of his darling."

Isaac Asimov Isaac Asimov ( ; – April 6, 1992) was an Russian-born American writer and professor of biochemistry at Boston University. During his lifetime, Asimov was considered one of the "Big Three" science fiction writers, along with Robert A. H ...

used the term ''bug'' to relate to issues with a robot in his short story " Catch That Rabbit", published in 1944. Computer pioneer and rear admiral, Grace Hopper, popularized a story about a

moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...

that caused a problem in an early

electromechanical Electromechanics combine processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focus on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each ...

computer. While Hopper was working on the Mark II and Mark 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." Reportedly, the operators, including William "Bill" Burke, later of the Naval Weapons Laboratory, Dahlgren, Virginia, were familiar with the engineering term and probably making a

joke A joke is a display of humour in which words are used within a specific and well-defined narrative structure to make people laugh and is usually not meant to be interpreted literally. It usually takes the form of a story, often with dialogue, ...

by conflating the two meanings of bug (biological and defect). Although probably a joke, the story indicates that the term was commonly used in the computer field at that time. Log Book With Computer Bug
", National Museum of American History, Smithsonian Institution. The log book, complete with moth, is part of the collection of the Smithsonian

National Museum of American History The National Museum of American History: Kenneth E. Behring Center is a historical museum in Washington, D.C. It collects, preserves, and displays the heritage of the United States in the areas of social, political, cultural, scientific, and m ...

. The related term ''

debug In engineering, debugging is the process of finding the root cause, workarounds, and possible fixes for bugs. For software, debugging tactics can involve interactive debugging, control flow analysis, log file analysis, monitoring at the ap ...

'' also appears to predate its usage in computing: the ''

Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary of the English language, published by Oxford University Press (OUP), a University of Oxford publishing house. The dictionary, which published its first editio ...

''s etymology of the word contains an attestation from 1945, in the context of aircraft engines.''Journal of the Royal Aeronautical Society''. 49, 183/2, 1945 "It ranged ... through the stage of type test and flight test and 'debugging' ..."

"It's not a bug, it's a feature"

Since ''bug'' implies undesirable behavior, calling a behavior a bug is subjective. Behavior which is considered a bug by some may be considered a useful feature by others, hence a common phrase is "It's not a bug, it's a feature" (INABIAF). This quip is recorded in

The Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANE ...

dating to 1975 but dates to 1971 when

PDP-8 The PDP-8 is a family of 12-bit minicomputers that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units sold during the model's lifetime. Its basic design follows the pi ...

programmer Sandra Lee Harris at

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...

(DEC) made the distinction between issues to be fixed in the code for DEC's FOCAL interpreter and those to be documented or clarified in the user manual. Such behavior might be explicitly communicated to users, or might remain an undocumented feature.

References

{{reflist Engineering concepts Engineering