Pronounced "dee-mun" as in the word "demon," it is a Unix program that executes in the background ready to perform an operation when required. Functioning like an extension to the operating system, a daemon is usually an unattended process that is initiated at startup. Typical daemons are print spoolers and e-mail handlers or a scheduler that starts up another process at a designated time. The term comes from Greek mythology meaning "guardian spirit." See agent and mailer-daemon.