Types of MCI Messages

The MCI commands divide into the following categories:

• Required commands are supported by all MCI device drivers.
• Basic commands are optionally supported by some devices.
• 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.
• System commands are interpreted directly by MCI rather than being relayed to a device.

Your device driver must support all required command messages. These messages represent the minimum command set for an MCI device driver.

While your device driver might optionally support the basic commands, it must recognize and respond to all of them. If your device driver does not support one of these messages, it must respond to it by returning the error code MCI_UNSUPPORTED_FUNCTION. If your device driver does support a basic command message, it must also respond to all of its basic options.

Your device driver might add options to the required or basic command sets, or create new command messages to form an extended command set. If your device driver extends the command set for an existing device type, you should base your extended command set on one already defined. (For example, if you are developing a device driver for a new videodisc player, you should base your extended commands on the commands already defined for videodisc players.)

Your device driver does not respond to system commands. MCI manages these messages.