The following example shows the elements of a debugger diagnostic
    message:

    %DEBUG-W-NOSYMBOL, symbol 'X' is not in the symbol table
      1   2    3                        4

    1  The facility name (DEBUG).

    2  The severity level (W, in this example).

    3  The message identifier (NOSYMBOL, in this example). The
       message identifier is an abbreviation of the message text.

    4  The message text.

    The identifier enables you to find the explanation for a
    diagnostic message from the debugger's online help (and the
    action you need to take, if any).