The ALERT.H header file contains data structures for predefined alert classes. These structures define only the fixed-length part of the information, not the ASCIIZ strings that follow some of the structures.

There are five alert types, but only four of these are actual data structures. These data structures are arrays, represented by square brackets ([]). The Network Message Received alert is not a data structure because it consists only of the ASCIIZ string of message text received. Each of the five alert types is described in the following sections.