Software defect (nonfiction)

A page from the Harvard Mark II electromechanical computer's log, featuring a dead moth that was removed from the device.

A software defect (or 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.

A program that contains a large number of defects, and/or defects that seriously interfere with its functionality, is said to be buggy.

In his memoirs, pioneering computer scientist Maurice Wilkes (nonfiction) wrote:

I well remember when this realization first came on me with full force. The EDSAC was on the top floor of the building and the tape-punching and editing equipment one floor below. [...] It was on one of my journeys between the EDSAC room and the punching equipment that "hesitating at the angles of stairs" the realization came over me with full force that a good part of the remainder of my life was going to be spent in finding errors in my own programs.