DEFINITION OF BUG. .?. .

What is a bug?

A bug is an error or defect in the software. A behavior is deemed a bug if the software doesn't perform as required, specified or expected.

Why error or a defect is called a bug?

The legend goes that the first digital computer, ENIAC, was having a malfunction. Lt. Grace Hopper, looking in the hardware components, found a moth trapped in the boards.

"Oh, it's just a bug."

However, The New Hacker's Dictionary [Eric Raymond, Second Edition, MIT Press, (1994)] states that the term was used prior to that event. Even so, the legendary moth is now reputed to be property of the Smithsonian Institute.