Message names, like function names, begin with a prefix. Related messages are grouped together with a common prefix. An underscore character (_) follows the prefix in each message name. One or more words describing the purpose of the message appear after the underscore. Message names use only uppercase letters.
The following is an example of a message name:
WOM_CLOSE
The prefix (WOM) indicates that the message is a waveform output message. The descriptive portion of the message (CLOSE) indicates the purpose of the message. This message is sent whenever a waveform output device is closed.