MCI
Command Strings and Messages
MCI supports
command strings and command messages. You can use either strings or messages,
or both, in your MCI application.
The command-message interface
consists of constants and structures. You use the mciSendCommand function to send a message
to an MCI device.
The command-string interface
provides a textual version of the command messages. You use the mciSendString function to send a string
to an MCI device. Command strings duplicate the functionality of the command
messages. The Microsoft Windows operating system converts the command strings
to command messages before sending them to the MCI driver for processing.
The command
messages that retrieve information do so in the form of structures, which are
easy to interpret in a C application. These structures can contain information
on many different aspects of a device. The command strings that retrieve
information do so in the form of strings, and can only retrieve one string at a
time. Your application must parse or test each string to interpret it. You
might find that the command messages are easier to use than the command strings
in some cases, but the command strings are easy to remember and implement. Some
MCI applications use command strings when the return value will not be used
(other than to verify success) and command messages when retrieving information
from the device.
When commands
are discussed, this overview uses the string form of the command followed by
the message form in parentheses.