Before playing or recording MIDI data, you must determine the capabilities of the MIDI hardware present in the system. MIDI capability can vary from one multimedia computer to the next; applications should not make assumptions about the hardware present in a given system.
Windows provides the following functions to determine how many MIDI devices are available for input or output in a given system:
| midiInGetNumDevs | Retrieves the number of MIDI input devices present in the system. |
| midiOutGetNumDevs | Retrieves the number of MIDI output devices present in the system. |
Like other audio devices, MIDI devices are identified by a device identifier, which is determined implicitly from the number of devices present in a given system. Device identifiers range from zero to the number of devices present, minus one. For example, if there are two MIDI output devices in a system, valid device identifiers are 0 and 1.
After you determine how many MIDI input or output devices are present in a system, you can inquire about the capabilities of each device. Windows provides the following functions to determine the capabilities of audio devices:
| midiInGetDevCaps | Retrieves the capabilities of a given MIDI input device and places this information in the MIDIINCAPS structure. |
| midiOutGetDevCaps | Retrieves the capabilities of a given MIDI output device and places this information in the MIDIOUTCAPS structure. |
Each of these functions has a parameter specifying the address of a structure that the function fills with information about the capabilities of a specified device.