bug

Coding error in a computer program that prevents it from functioning as designed. Most software companies have a quality-assurance department which is charged with finding program bugs while the program is in development (debugging); bugs are also often detected by means of beta testing (testing of a product, often by potential consumers, before it is placed on the market). The term originated in a computer context in 1945 when a moth flew into and jammed an electrical relay of the Harvard Mark II computer; it was extracted and taped into the log book with the inscription “First actual case of bug being found” (the term having previously been used for other kinds of mechanical defects).

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