Windows defines the following data types for the MIDI input functions:
| HMIDIIN | Handle of a MIDI input device. |
| MIDIHDR | Header for a stream buffer or a block of MIDI system-exclusive data. For input applications, this structure records only system-exclusive data (streaming is not supported for MIDI input). |
| MIDIINCAPS | Structure used to inquire about the capabilities of a MIDI input device. |