ON- LINE
The status of a device or hardware subsystem that is currently physically and logically connected with a separate controlling system, such as a CPU, where the controlling system is controlling I/O from the device or subsystem. Compare with Off-Line. The status of a human user that is currently logged onto a session with a computer or network system that is physically separate from the user's terminal or workstation. A system supporting interactive user or device activity where all I/O is controlled by a central controller, such as a mainframe CPU, usually using synchronous, polled I/O. Compare with real-time.
More: Hardware User System