Event Class Numbers
If you define your own event classes, you must associate it with an event class number. Event class numbers are 32-bit integers. Each event class number is a tuple made up of a set ID and the class event ID. The set ID corresponds to a set of event classes and is assigned by OSF to an organization or vendor. The class event ID identifies an event class within the set of event classes. The organization or vendor manages the issuance of the class ID numbers to generate an event class number.
The structure and administration of event class numbers can be likened to the structure and administration of IP addresses. Recall that an IP address is a tuple of a network ID (analogous to the set ID) and a host ID (analogous to the class event ID).