Information system

1. A system, whether automated or manual, that comprises people, machines, and/or methods organized to collect, process, transmit, and disseminate data that represent user information.

2. Any telecommunications and/or computer related equipment or interconnected system or subsystems of equipment that is used in the acquisition, storage, manipulation, management, movement, control, display, switching, interchange, transmission, or reception of voice and/or data, and includes software, firmware, and hardware.

Source: from Federal Standard 1037C and from MIL-STD-188 and from the National Information Systems Security Glossary

In Dana Scott's domain theory (theory of computability and approximability), an information system is used as a representation of a domain.