A marker of some type used in processing or interpreting information; a signal indicating the existence or status of a particular condition. Flags are used in such areas as communication, programming, and information processing. A flag can be a code, embedded in data, that identifies some condition, such as the beginning or end of a word or a message; or it can be one or more bits set internally by hardware or software to indicate an event of some type, such as an error or the result of a comparison of values.