1. A computer that is attached to a network and provides services other than simply acting as a store and forward processor or communication switch. Host computers range in size from small microcomputers to large time-sharing or batch mainframes. Many networks have a hierarchical structure, with a communication subnetwork providing packet switching services for host computers to support time-sharing, remote job entry, etc. A host computer at one level of a hierarchy may function as a packet or message switch at another.

2. A computer used to develop software for execution on another computer, known as the target computer.

3. A computer used to emulate another computer, known as the target computer. See also emulation.