MCI Command Types

There are four types of MCI commands:

1. System commands

2. Required commands

3. Basic commands

4. Extended commands

System commands are not passed to an MCI driver. They are processed within winmm.dll.

Required commands are defined in the core command table. MCI drivers must recognize and process all required commands.

Basic commands are also defined in the core command table. MCI drivers must recognize all basic commands. However, if a basic command is not relevant to a particular device, the driver can simply return MCI_UNSUPPORTED_FUNCTION for that command.

Extended commands are those that are included in the device-type or device-specific command tables. Extended commands can either be modifications of the basic and required commands, or they can be new commands. An MCI driver only needs to recognize extended commands that are relevant for its device.

The following table lists the system, required, and basic commands. Extended commands are described within the Win32 SDK.

Command Type	Command String	Command Message
System Commands	break	MCI_BREAK
	sound	MCI_SOUND
	sysinfo	MCI_SYSINFO
Required Commands	capability	MCI_GETDEVCAPS
	close	MCI_CLOSE (Driver receives MCI_CLOSE_DRIVER.)
	info	MCI_INFO
	open	MCI_OPEN (Driver receives MCI_OPEN_DRIVER.)
	status	MCI_STATUS
Basic Commands	load	MCI_LOAD
	pause	MCI_PAUSE
	play	MCI_PLAY
	record	MCI_RECORD
	resume	MCI_RESUME
	save	MCI_SAVE
	seek	MCI_SEEK
	set	MCI_SET
	stop	MCI_STOP

All MCI commands are described in the Win32 SDK. To find the definition of a command, use the Win32 SDK keyword index to search for the command message (for example, MCI_SYSINFO).