Messages numbers displayed by ALP have the following format:
ALPnnnn:
Message numbers always have a three-letter prefix that designates the component issuing the message (ALP), followed by a four digit decimal number given by nnnn. All messages issued by the assembler are uniquely numbered; however, not all messages displayed by the assembler will be accompanied by a formatted message number (for instance, the assembler banner).
Messages issued during assembler initialization, command line processing, or exception handling are numbered from 0 to 999. Other messages occur during input stream processing and are grouped according to their severity type: 1000 through 1999 for fatal errors, 3000 through 3999 for regular errors, 4000 through 4999 for warnings, and 5000 through 5999 for informational messages.
It should be noted that messages are numbered for reference only; it is not guaranteed that messages will be numbered identically for each subsequent assembler release, or that individual messages will be retained or remain unmodified in future releases.