Preference file used by TwinCAT System Manager, a PLC (Programmable Logic Controller) management program; stores the configuration for a PLC system, including system relationships, PLC programs, axis control, and connected I/O channels.

TwinCAT System Manager can configure several types of buses, including USB, serial, Ethernet, EtherCAT, Beckhoff Lightbus, PROFIBUS, ProfiNET, Interbus, CANopen, SERCOS, DeviceNet, PC printer ports, and SMB.