The DCPU-16 supports up to 65535 connected hardware devices. These devices can be anything from additional storage, sensors, monitors or speakers. How to control the hardware is specified per hardware device, but the DCPU-16 supports a standard enumeration method for detecting connected hardware via the HWN, HWQ and HWI instructions.
Interrupts sent to hardware can't contain messages, can take additional cycles, and can read or modify any registers or memory adresses on the DCPU-16. This behavior changes per hardware device and is described in the hardware's documentation.