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A software bug is an error, flaw, failure, or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. Most bugs arise from mistakes and errors made by people in either a program's source code or its design, or in frameworks and operating systems used by such programs, and a few are caused by compilers producing incorrect code. A program that contains a large number of bugs, and/or bugs that seriously interfere with its functionality, is said to be ''buggy'' or defective. Reports detailing bugs in a program are commonly known as bug reports, defect reports, fault reports, problem reports, trouble reports, change requests, and so forth. Bugs trigger errors that can in turn have a wide variety of ripple effects, with varying levels of inconvenience to the user of the program. Some bugs have only a subtle effect on the program's functionality, and may thus lie undetected for a long time. More serious bugs may cause the program to crash or freeze. Others qualify as security bugs and might for example enable a malicious user to bypass access controls in order to obtain unauthorized privileges. The results of bugs may be extremely serious. Bugs in the code controlling the Therac-25 radiation therapy machine were directly responsible for some patient deaths in the 1980s. In 1996, the European Space Agency's US$1 billion prototype Ariane 5 rocket had to be destroyed less than a minute after launch, due to a bug in the on-board guidance computer program. In June 1994, a Royal Air Force Chinook helicopter crashed into the Mull of Kintyre, killing 29. This was initially dismissed as pilot error, but an investigation by ''Computer Weekly'' uncovered sufficient evidence to convince a House of Lords inquiry that it may have been caused by a software bug in the aircraft's engine control computer. In 2002, a study commissioned by the US Department of Commerce' National Institute of Standards and Technology concluded that "software bugs, or errors, are so prevalent and so detrimental that they cost the US economy an estimated $59 billion annually, or about 0.6 percent of the gross domestic product". == Etymology == Use of the term "bug" to describe inexplicable defects has been a part of engineering jargon for many decades and predates computers and computer software; it may have originally been used in hardware engineering to describe mechanical malfunctions. For instance, Thomas Edison wrote the following words in a letter to an associate in 1878: The Middle English word ''bugge'' is the basis for the terms "bugbear" and "bugaboo", terms used for a monster. Baffle Ball, the first mechanical pinball game, was advertised as being "free of bugs" in 1931.〔(【引用サイトリンク】title=Baffle Ball )〕 Problems with military gear during World War II were referred to as bugs (or glitches). The term "bug" was used in an account by computer pioneer Grace Hopper, who publicized the cause of a malfunction in an early electromechanical computer. A typical version of the story is given by this quote: Hopper was not actually the one who found the insect, as she readily acknowledged. The date in the log book was September 9, 1947,〔"(Bug )", ''The Jargon File'', ver. 4.4.7. Retrieved June 3, 2010.〕〔"(Log Book With Computer Bug )", National Museum of American History, Smithsonian Institution.〕 although sometimes erroneously reported as 1945.〔"(The First "Computer Bug )", Naval Historical Center. But note the Harvard Mark II computer was not complete until the summer of 1947.〕 The operators who did find it, including William "Bill" Burke, later of the Naval Weapons Laboratory, Dahlgren, Virginia,〔IEEE Annals of the History of Computing, Vol 22 Issue 1, 2000〕 were familiar with the engineering term and, amused, kept the insect with the notation "First actual case of bug being found." Hopper loved to recount the story. This log book, complete with attached moth, is part of the collection of the Smithsonian National Museum of American History.〔 The related term "debug" also appears to predate its usage in computing: the Oxford English Dictionary'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’ ..."〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Software bug」の詳細全文を読む スポンサード リンク
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