MCI command strings are sent to MCI device drivers with the mciSendString and mciExecute functions. The commands divide into the following categories:
System commands are interpreted directly by MCI rather than being relayed to a device.
Required commands are supported by all MCI devices.
Basic commands are optional commands. If a device uses a basic command, it must respond to all options for that command. If a device does not use a basic command, it will return “Action not available for this device.”
Extended commands are specific to a device type or device class, for example, videodisc players. These commands contain both unique commands and extensions to the required and basic commands.