Software is supposed to be error free, but all too often isn't. A mistake in a computerprogram is known as a bug-hence debuging refers to the process of correcting programming errors. According to legend, the first bug was an unlucky moth that was crushed to death in one of the relays of the electromechnanical Mark II computer, bringing the machine's operation to a screeching halt. the cause of the failure was discovered by Grace Happer, an early computer pioneer, who promptly taped the moth to her logbook, noting "First case of bug being found".