Bug

A bug or program flaw is a defect in the software (error) that occurs, for example, in a project or in the operation of the program. It causes incorrect or unexpected results, or system behavior in an unintended way.

The process of finding and fixing errors is known as debugging, and it often uses formal techniques or tools to detect errors. Since the 1950s, some computer systems have been designed to prevent, detect, or automatically correct various "computer errors" during operation.