EPICS interfaces to the real world with IOCs (Input Output Controllers) . These are either stock-standard PCs or VME standard embedded system processors that manage a variety of "plug and play" modules (GPIB, RS-232, IP Carrier etc.) which interface to control system instruments (oscilloscopes, network analyzers) and devices (motors, thermocouples, switches, etc.). The IOC holds and runs a database of 'records' which represent either devices or aspects of the devices to be controlled. IOC software used for hard-real-time normally use RTEMS or VxWorks, though work has been ongoing in porting to other systems. Soft real-time IOC software sometimes runs on Linux or MS-Windows based machines.

Other computers on the network can interact with the IOC via the concept of channels. Take, for example a particle accelerator with shutters between sectors. There would typically be several channels corresponding to a shutter: an output channel to activate shutter motion, an input channel to see the status of the shutter (e.g. shut, open, moving, etc.), and probably some additional analog input channels representing temperatures and pressures on each side of the shutter. Channel names are typically in the form EQUIPMENT:SIGNALNAME (e.g. ACCELERATOR_RING:TEMP_PROBE_4, although they can be much less verbose to save time).

Most operations are driven directly from a standalone GUI package such as EDM (editor/display manager) or MEDM (Motif/EDM). These allow creation of GUI screens with dials, gauges, text boxes, simple animations, etc.

However it is not just GUI software which can interact with EPICS: any software which can speak the CA protocol can get and put values of records. For example on the EPICS website there are several extension packages which allow CA support in things like MATLAB, LabVIEW, Perl, Python, Tcl, ActiveX, etc. Hence it is easy to do things like make scripts which can activate EPICS controlled equipment.