To operate in a way identical to a different system. For example, the Apple II 2780/3780 Protocol Emulator and the Apple II 3270 BSC Protocol Emulator, together with the Apple Communications Protocol Card (ACPC), allow the Apple II, Apple II Plus, or Apple IIe to emulate the operations of IBM 3278 and 3277 terminals and 3274 and 3271 control units.